JP5440893B2 - Information processing apparatus, information processing method, reflector, and communication system - Google Patents

Description

  The present invention relates to an information processing apparatus and information processing method for performing wireless communication with a reflector via radio waves, a reflector, and a communication system.

  In recent years, the use of RFID (Radio Frequency Identification) tags (wireless tags) has become widespread. RFID tags are expected to replace barcodes, particularly in the field of logistics, and are expected to become widespread in the near future.

  Currently, the frequency band for RFID tags includes a 13.56 MHz band, a so-called UHF band of around 800 MHz to 950 MHz, and a 2.45 GHz band. Among these, UHF band and 2.45 GHz band radio waves (Radio Wave) have the advantage of easily extending the communication distance compared to 13.56 MHz band radio waves. In addition, the UHF band radio wave has an advantage that it easily sneaks into the shadow as compared to the 2.4 GHz band radio wave. For this reason, development of RFID tags and reader / writers that use radio waves in the UHF band is underway.

  When using radio waves in the UHF band, the distance over which the reader / writer can communicate with the wireless tag may be extended from about several tens of centimeters to about several meters, compared to the case where the current mainstream 13.56 MHz band radio waves are used. it can. Therefore, if a UHF band radio wave is used, the communication area, which is a space area in which the reader / writer can communicate with the wireless tag, can be expanded to a relatively wide range.

  In order to estimate the position of such an RFID tag, a technique for measuring the distance from a communication station that communicates with the RFID tag has been proposed. As one example, a technology in which a number of base stations receive signals from an active IC tag as an RFID tag, and a distance and a position are estimated based on the received signals from the active IC tag at each base station. There is. In this example, the distance between each base station and the active IC tag is estimated based on the strength of the received signal from the active IC tag. That is, the distance is estimated using the correlation between the intensity of the received signal and the distance. Also, a method of estimating the distance of the active IC tag by measuring the amount of delay of the reception timing by providing an access point with a known position and simultaneously transmitting a signal from the active IC tag and the access point is also adopted. ing.

  Further, in Patent Document 1, as shown in FIG. 38, in the RF communication system, signals 40 and 42 having different frequencies are transmitted from the interrogator 36 as a reader to the RF tag 38. A technique is disclosed in which the distance between the interrogator 36 and the RF tag 38 is estimated by counting the number of null points of the synthesized wave on which signals are superimposed.

  Further, in Patent Document 2, as shown in FIG. 39, in a communication device 138 that performs radio communication with an RFID tag, a reflected signal from the RFID tag is received via an antenna 140 and a received signal input from a circulator 92 is received. And the carrier signals input from the circulator 90 and the splitter 98 are multiplied by the mixers 100 and 102 to generate an I signal and a Q signal. Based on the I signal and the Q signal, a reflected signal from the RFID tag is generated. A technique for calculating the amplitude and phase is disclosed. Further, it is disclosed that the distance to the RFID tag is obtained using the phase difference between the carrier signal and the reflected signal of the RFID tag.

  On the other hand, a technique for detecting whether or not an RFID tag is present in a predetermined area using a technique for measuring the distance to the RFID tag has been proposed.

  For example, Patent Document 3 discloses a reading device that reads a model piece tag for each section mounting surface and reads information on the model piece tag placed on the section mounting surface.

  Patent Document 4 discloses that a dog is based on whether information obtained from a position detection device having a GPS or the like provided on a dog collar indicates that the dog is located outside a predetermined stray dog detection area. A technique for determining whether or not the dog is a lost dog is disclosed.

Further, Patent Document 5 discloses a technique in which at-home alert processing is automatically executed when all of a plurality of mobile localizers enter the inside alert surface.
JP-T-2004-507714 (Fig. 2 etc.) European Patent Application No. 1239634 (FIG. 3 etc.) Utility Model Registration No. 3069344 (first page, FIG. 1 etc.) US Patent Application Publication No. 2004/0189477 (first page, FIG. 1 etc.) US Patent Application Publication No. 2005/0073404 (first page, FIG. 1 etc.)

  When an RFID communication system using UHF band radio waves is used, long-distance communication is possible, so that communication is possible even for remote RFID tags that do not need to be processed, and there is no need for such RFID tags. Problems such as troublesome processing and degradation of response performance due to the influence of multipath arise. In order to solve these problems, a method is conceivable in which the reader / writer obtains the distance to each RFID tag, and thereby sorts the RFID tags that are to be subjected to processing such as analysis / rewriting of the data portion. Here, as a method for obtaining the distance between the reader / writer and the RFID tag, there are the following problems when the above-described conventional technique is used.

  First, when estimating the distance based on the reception intensity of the signal from the RFID tag and the delay time, there is a problem that the distance measurement accuracy is low. The accuracy when the distance is estimated by such a method is actually about 1 m to several m. For example, when applied to a physical distribution management system or the like, this level of accuracy is not practical and higher distance measurement accuracy is required.

  In the technique disclosed in Patent Document 1, since the distance is estimated by counting the number of null points of the synthesized wave obtained by superimposing two signals having different frequencies, the distance accuracy is very high. There is a problem of being bad. More specifically, according to the example described in paragraph [0025] of Patent Document 1, when the first signal of 880 MHz and the second signal of 884 MHz are used, the distance from the interrogator 36 is about 37.5 m. Null points occur at approximately 75 m, and additional null points occur approximately every 75 m thereafter. For example, if three nulls are counted between the interrogator 36 and the RF tag 38, the estimated distance between the interrogator 36 and the RF tag 38 is 187.5 m or more and less than 262.5 m. The range is 75 m. When multipath occurs, there is a problem that the propagation distance of the radio signal becomes long and a distance different from the actual distance of the RFID tag is calculated.

  As described above, since the distance measurement accuracy cannot be increased in the conventional technique, the measurement accuracy of the position of the RFID tag calculated based on the result of the distance measurement cannot be increased. Therefore, by detecting the position of the RFID tag and determining whether or not the RFID tag exists at a predetermined position, it is determined whether or not the RFID tag is a target to be subjected to processing such as analysis / rewriting of the data portion. In the case of performing the process of classifying these, since the accuracy of detecting the position of the RFID tag is not high, it is not possible to accurately determine whether or not the RFID tag is in a predetermined position. There is a problem that the accuracy of sorting the RFID tags to be performed is lowered, and the processing accuracy is lowered.

  The present invention has been made in view of the above problems, and an object thereof is to provide an information processing apparatus, an information processing method, a reflector, and a communication system that can accurately measure the distance of an RFID tag. It is to provide. In addition, the purpose includes providing an information processing apparatus, an information processing method, a reflector, and a communication system that can measure the distance of the RFID tag without using a special RFID tag. Furthermore, the purpose of the information processing apparatus and information is to be able to classify the RFID tag to be processed with high accuracy according to the position where the RFID tag exists and to perform different processing on the classified RFID tag. To provide a processing method, a reflector, and a communication system.

  In order to solve the above-described problems, an information processing apparatus according to the present invention transmits a request signal, which is a signal composed of one frame, using radio waves having a plurality of different carrier frequencies, and transmits the request signal using the transmission unit. The received signal is reflected by a reflector while receiving a predetermined modulation, and a reflected signal that is a signal composed of one frame is received via an antenna, and the receiving means receives the reflected signal. A phase information acquisition unit that calculates the amount of phase change between the reflected signal and the request signal for each carrier frequency transmitted by the transmission unit, and a phase change for each carrier frequency acquired by the phase information acquisition unit. A distance calculating unit that calculates a distance between the antenna and the reflector based on an amount and a carrier frequency; and the reflector based on the distance calculated by the distance calculating unit A position information acquisition unit that acquires position information that is information related to a position, and based on the position information acquired by the position information acquisition unit, determines whether or not the reflector exists at a predetermined position, and a determination result And a processing unit that performs a predetermined process based on the determination result.

  Here, the reflector is, for example, an RFID tag including an IC (Integrated Circuit) for wireless communication, a storage unit, and an antenna. An RFID tag does not have a power source such as a battery, and a circuit is operated by power transmitted by radio waves from a reader / writer, and a passive type RFID tag that performs wireless communication with the reader / writer or a power source such as a battery. An active type RFID tag is included. An RFID tag having unique ID information is also included.

  With such a configuration, the phase change amount of the reflected signal at each carrier frequency is acquired, and the distance is calculated from the phase change amount and the carrier frequency. Here, although details will be described later, the distance can be accurately calculated if the phase change amount and the carrier frequency of the signal due to the plurality of carrier frequencies are obtained. In particular, when calculating the distance using the reflection signals of a plurality of frames, if the reflector is moving, the calculated distance is also large because the reflector moves while the reflection signals are sequentially transmitted. Although an error may occur, in the present invention, the distance can be calculated using the reflection signal composed of one frame, so that a plurality of such reflection signals are transmitted even when the reflector is moving. Therefore, it is possible to reduce a distance calculation error caused by the interval between the reflected signals. That is, according to the configuration as described above, it is possible to accurately calculate the distance accurately by receiving the reflection signal transmitted from the reflector, and to accurately detect the position of the reflector, Processing according to the position of the reflector can be performed with high accuracy.

  In the information processing apparatus according to the present invention, in the information processing apparatus, the reception unit receives the reflected signal via a plurality of antennas, and the phase information acquisition unit includes the plurality of antennas. The amount of phase change is calculated for each received reflected signal, and the distance calculation unit is based on the amount of phase change calculated for each reflected signal received via the plurality of antennas. Calculating the distance between the plurality of antennas and the reflector, and the position information acquisition unit obtains the position information of the reflector based on the distance between the plurality of antennas and the reflector. It is an information processing apparatus to acquire.

  With this configuration, the detailed position of the reflector, for example, the x coordinate, the y coordinate, the z coordinate, and the like can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  The information processing apparatus of the present invention further includes an area information storage unit that stores area information that is information about a predetermined area in the information processing apparatus, and the position determination unit is acquired by the position information acquisition unit. In this information processing apparatus, the position information is compared with the area information to determine whether or not the reflector is arranged at the predetermined position, and to obtain a determination result.

  With this configuration, different processing can be performed depending on whether or not the reflector is present in a predetermined region.

  Further, the information processing apparatus according to the present invention is the information processing apparatus, wherein the information processing apparatus further includes a self-position information acquisition unit that acquires self-position information that is information related to a position of the self-device, and the position determination unit Determines whether or not the reflector is disposed at the predetermined position by determining whether or not the position information acquired by the position information acquisition unit and the own position information satisfy a predetermined relationship. This is an information processing apparatus that determines a determination result and obtains a determination result.

  With this configuration, different processing can be performed depending on the relative positional relationship between the reflector and the information processing apparatus.

  In the information processing apparatus according to the present invention, in the information processing apparatus, the processing unit may receive the reflection received by the reception unit when the determination result indicates that the reflector is present at the predetermined position. An information processing apparatus that outputs a signal.

  With this configuration, it is possible to output only the reflected signal received from the reflector present at a predetermined position, for example, to another device.

  In the information processing apparatus according to the aspect of the invention, in the information processing apparatus, the processing unit may perform predetermined processing on the reflector when the determination result indicates that the reflector is present at the predetermined position. It is the information processing apparatus which transmits the information.

  With this configuration, it is possible to transmit predetermined information only to the reflector present at a predetermined position.

  The information processing apparatus according to the present invention is the information processing apparatus, wherein the processing unit outputs a control signal for controlling communication with the reflector based on the determination result.

  With such a configuration, for example, it is possible to enable communication only with a reflector present at a predetermined position.

  The information processing apparatus according to the present invention includes an obstacle information storage unit that can store obstacle information that is information on an obstacle arranged in a communication path between the reflector and the antenna. And a correction unit that corrects the position information of the reflector based on the obstacle information, and the position determination unit is configured such that the reflector is a predetermined value based on the position information corrected by the correction unit. It is an information processing apparatus which determines whether it exists in the position of and acquires a determination result.

  With this configuration, it is possible to correct the position information of the erroneously detected reflector due to the influence of the obstacle, and it is possible to obtain highly accurate position information of the reflector. As a result, different operations can be performed depending on the more accurate position of the reflector.

  In the information processing apparatus of the present invention, in the information processing apparatus, the transmission unit sets a plurality of divided periods within a period in which one request signal is transmitted, and the carrier frequencies differ from each other in each divided period. It is the information processing apparatus to control to.

  With this configuration, the distance can be calculated only by transmitting one reflected signal, so that transmission / reception of signals necessary for calculating the distance can be reduced, thereby improving communication efficiency. The distance can be calculated without dropping. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  The information processing apparatus according to the present invention is an information processing apparatus that controls the transmission unit so that the request signal is transmitted by one carrier frequency composed of different carrier frequency components.

  With this configuration, the distance can be calculated only by transmitting one reflected signal, so that transmission / reception of signals necessary for calculating the distance can be reduced, thereby improving communication efficiency. The distance can be calculated without dropping. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  Further, in the information processing apparatus of the present invention, in the information processing apparatus, a reflection signal is transmitted from the reflector at three or more different carrier frequencies, and the phase information acquisition unit is configured to transmit a signal of each carrier frequency. Among these, the information processing apparatus acquires a phase change amount by selecting signals of two carrier frequencies that satisfy a predetermined criterion when the signal state calculates the distance.

  In the reflected signal, depending on the carrier frequency, it may be considered that the state of the signal is not suitable for calculating the distance due to the occurrence of multipath, for example. On the other hand, according to the above-described configuration and method, signals having two carrier frequencies satisfying a predetermined criterion in calculating the distance among the three or more different carrier frequencies are selected. Thus, since the phase change amount is detected based on these, it is possible to improve the accuracy of the phase change amount detection. Therefore, it is possible to improve the accuracy of distance calculation. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  In the information processing apparatus according to the present invention, in the information processing apparatus, the reception unit includes a frequency conversion unit that performs frequency conversion processing of the received reflected signal, and the frequency conversion unit converts the reflected signal into an I signal. And Q signal.

  With this configuration, the received reflected signal is converted into an I signal and a Q signal, thereby performing frequency conversion. This makes it easy to detect the phase.

  The information processing apparatus according to the present invention is an information processing apparatus in which the distance calculation unit calculates the distance using a high-resolution spectrum analysis method in the information processing apparatus.

  Conventionally, the high-resolution spectrum analysis method is used for the purpose of estimating the arrival direction of radio waves by using reception signals received by a plurality of antenna elements as inputs. On the other hand, in the above configuration and method, the received signal from each antenna element in the direction-of-arrival estimation by the conventional high-resolution spectrum analysis method is replaced with the reception signal of each carrier frequency described above. The distance is estimated by changing the application model.

  With such a high-resolution spectrum analysis method, it is possible to calculate the estimation target value with the most probable value, so even if multipath occurs, it is possible to exclude this multipath distance. It becomes. That is, according to the above-described configuration and method, it is possible to accurately calculate the distance even when multipath occurs. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  Further, in the information processing apparatus of the present invention, in the information processing apparatus, the distance calculation unit uses a MUSIC (Multiple Signal Classification) method as the high resolution spectrum analysis method, and inputs a plurality of different ones as an input of the MUSIC method. An information processing apparatus that uses a reflected signal received by a carrier frequency, calculates a MUSIC evaluation function using a mode vector as a function of the distance, and calculates the distance by calculating a peak value of the MUSIC evaluation function.

  Here, although the peak value of the MUSIC evaluation function usually appears only at one location, for example, when multipath occurs, peak values may appear at a plurality of locations. Even in this case, since the distance corresponding to the multipath is longer than the distance to be calculated, the multipath is generated by setting the smallest distance among the distances where the peak is generated as the distance to be calculated. It is also possible to calculate the distance accurately. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  The information processing apparatus according to the present invention is the information processing apparatus in which the distance calculation unit calculates the distance by using the received intensity of the received reflected signal together.

  With this configuration, the distance is calculated based also on the reception intensity of the reflected signal. For example, when there are a plurality of distance value candidates, an appropriate distance is selected by considering the reception intensity. It becomes possible to calculate the distance more accurately. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  In the information processing apparatus of the present invention, in the information processing apparatus, the information of the data part included in the reflected signal is acquired, and the distance information calculated by the distance calculation part and the information of the data part are obtained. The information processing apparatus includes a reception control unit that outputs the data to the outside.

  With this configuration, for example, information for identifying the reflector that has transmitted the reflection signal can be recognized based on the information of the data portion included in the reflection signal. The reception control unit recognizes the distance information measured by the distance calculation unit and the information of the data unit in association with each other. As a result, even when there are a plurality of reflectors with which the information processing apparatus communicates, the distances between the reflectors can be distinguished and recognized. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  The information processing apparatus according to the present invention is an information processing apparatus in which, in the information processing apparatus, the distance calculation unit measures a direction in which a reflector that has transmitted the reflection signal is positioned based on the reflection signal.

  With this configuration, it is possible to recognize not only the distance of the reflector but also the direction of the existing position. This makes it possible to recognize the position of the reflector. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  The information processing apparatus according to the present invention is the information processing apparatus according to the information processing apparatus, wherein the distance calculation unit calculates the distance by analyzing a signal in a preamble portion of the reflected signal.

  With this configuration, the distance is calculated by analyzing the signal in the preamble portion of the reflected signal. Here, the preamble portion indicates data indicating the start of the reflected signal, and is within predetermined data common to all reflectors within the same standard (for example, EPC). Therefore, since the length of the preamble part is the same regardless of the signal from any reflector, the signal can be analyzed reliably. Further, since all signals in the preamble part are common, for example, it is possible to calculate the distance even when PSK modulation is performed. As a result, the position of the reflector can be detected with high accuracy, and processing according to the position of the reflector can be performed with high accuracy.

  The information processing method of the present invention includes a transmission step of transmitting a request signal, which is a signal composed of one frame, using radio waves having different carrier frequencies, and the request signal transmitted in the transmission step is reflected. A reception step of receiving, via an antenna, a reflection signal that is a signal composed of one frame, which is generated by being reflected while being subjected to predetermined modulation by the body, and the reflection signal received in the reception step and the request signal Based on the phase information acquisition step for calculating the phase change amount for each carrier frequency transmitted by the transmission means, and the phase change amount and carrier frequency for each carrier frequency acquired by the phase information acquisition step A distance calculating step for calculating a distance between the antenna and the reflector, and a distance calculated in the distance calculating step. A position information acquisition step for acquiring position information which is information relating to the position of the reflector, and based on the position information acquired in the position information acquisition step, whether or not the reflector is present at a predetermined position. An information processing method comprising: a position determination step for determining and outputting a determination result; and a processing step for performing a predetermined process based on the determination result.

  With this configuration, by receiving a reflected signal transmitted from the reflector, the distance can be calculated accurately and accurately, the position of the reflector can be detected with high accuracy, and the distance corresponding to the position of the reflector can be determined. Processing can be performed with high accuracy.

  Further, the communication system according to the present invention includes an information processing apparatus according to the present invention and an article, a person associated with the reflector based on a result of communication with the reflector by the information processing apparatus. , And a management device that manages at least one of the organisms.

  With such a configuration, it is possible to easily construct a system capable of executing processing according to position information when managing articles, people, and living organisms associated with the reflector.

  As described above, the information processing apparatus according to the present invention is a distance measuring device that performs processing for receiving reflected signals transmitted from a plurality of different carrier frequencies from the reflector, and the reflection transmitted from the reflector. It is a structure provided with the distance calculation part which calculates the distance of this reflector and the said distance measurement apparatus by analyzing a signal. Thereby, it becomes possible to calculate the distance between the reflector and the distance measuring device more accurately.

  By using these configurations, it is possible to classify the RFID tag to be processed with high accuracy according to the position where the RFID tag exists, and to perform different processing on the sorted RFID tag. There is an effect.

  Hereinafter, an information processing apparatus will be described as an embodiment of the present invention with reference to the drawings. In addition, since the component which attached | subjected the same code | symbol in embodiment performs the same operation | movement, description may be abbreviate | omitted again.

(Embodiment 1)
(Configuration of reader / writer)
FIG. 2 is a block diagram illustrating a schematic configuration of a communication system including the RFID tag and the reader / writer according to the present embodiment. As shown in the figure, the communication system includes one or more RFID tags 1 (reflectors)... And a reader / writer (information processing apparatus) 2.

  The RFID tag 1 is attached to various articles, and records information on the attached article or related items and people. The RFID tag 1 includes a wireless communication IC (Integrated Circuit), a storage unit, an antenna, and the like.

  In the present embodiment, the RFID tag 1 does not have a power source such as a battery, and a passive RFID that performs wireless communication with the reader / writer 2 by operating a circuit with power transmitted by radio waves from the reader / writer 2. It is assumed that tags will be used. The RFID tag used in the present embodiment is not limited to the passive RFID tag as described above, and may be an active RFID tag having a power source such as a battery.

  The reader / writer 2 is a device that performs wireless communication with each RFID tag 1 and reads / writes information stored in the RFID tag 1. In the present embodiment, the reader / writer 2 reads and writes information stored in the RFID tag 1, but the present invention is not limited to this, and the information stored in the RFID tag 1 is read. It may be an RFID reader that performs only the above.

  In this embodiment, the frequency band of the radio wave transmitted and received by the reader / writer 2 is a so-called UHF band of about 800 MHz to 960 MHz. By using radio waves in such a frequency band, the reader / writer 2 can communicate with the RFID tag 1 located within a distance range of several meters to several tens of meters. In the present embodiment, communication using the UHF band is assumed. However, the present invention is not limited to this, and the 13.56 MHz band, 2.45 GHz band, and the like as frequency bands for RFID tags are used. A frequency band may be used, and further, communication using another frequency band capable of performing wireless communication may be performed.

  The reader / writer 2 includes a transmission antenna 3, a reception antenna 4, a transmission processing unit 5, a reception processing unit 6, a communication control unit 7, a position measurement unit 8, an external communication unit 9, an area determination unit 10, and an area information storage unit 11. It has a configuration with.

  The transmission antenna 3 is an antenna that transmits radio waves to the RFID tags 1... And the reception antenna 4 is an antenna that receives radio waves transmitted from the RFID tags 1. The transmission antenna 3 and the reception antenna 4 are configured by, for example, a patch antenna or an array antenna. In this configuration example, the transmitting antenna 3 and the receiving antenna 4 are provided separately, but one antenna may be used as having both functions of the transmitting antenna 3 and the receiving antenna 4.

  The transmission processing unit 5 performs processing such as modulation and amplification of a transmission signal transmitted from the transmission antenna 3. The reception processing unit 6 performs processing such as amplification and demodulation of the reception signal received by the reception antenna 4.

  The communication control unit 7 performs reading and / or writing control of information with respect to the RFID tag 1 to be communicated via the transmission antenna 3 and / or the reception antenna 4.

The transmission processing unit 5 and the part that performs processing related to the transmission of the communication control unit 7 constitute a transmission unit that transmits a transmission signal to the RFID tag 1. This transmission means may include the transmission antenna 3. Further, the communication control unit 7 may not be included in this transmission means.
The reception processing unit 6 and the part that performs processing related to reception by the communication control unit 7 constitute reception means for receiving a signal transmitted from the RFID tag 1, for example, a reflected signal. This receiving means may include the receiving antenna 4. Further, the communication control unit 7 may not be included in this transmission means.

  The position measuring unit 8 measures the position of the RFID tag 1 based on the received signal received from the RFID tag 1. Although details will be described later, the position of the RFID tag 1 is measured by measuring the distance between the reader / writer 2 and the RFID tag 1, measuring the direction of the RFID tag 1 when viewed from the reader / writer 2, and the RFID tag 1. Measurement of the spatial position. Strictly speaking, the distance between the reader / writer 2 and the RFID tag 1 corresponds to an average of the distance between the transmission antenna 3 and the RFID tag 1 and the distance between the RFID tag 1 and the reception antenna 4 in the reader / writer 2. To do. When the RFID tag 1 is an active type, this corresponds to the distance between the receiving antenna 4 and the RFID tag 1.

  The area determination unit 10 determines whether the RFID tag 1 is located within a predetermined space area (communication area) based on the position measured by the position measurement unit 8. Area information about what kind of spatial area the communication area is stored in the area information storage unit 11. The area determination unit 10 determines whether or not the position measured by the position measurement unit 8 exists in the communication area defined by the area information, so that the RFID tag 1 exists in the communication area. Judge whether it is.

  The external communication unit 9 transmits information on the RFID tag 1 read by the reader / writer 2 to an external device, and receives write information on the RFID tag 1 from the external device. Communication between the external device and the external communication unit 9 is established by wired or wireless communication. Here, the external device that operates based on the read / write processing on the RFID tag 1 by the reader / writer 2 may be configured to incorporate the reader / writer 2.

  The area information stored in the area information storage unit 11 is set according to the environment in which the reader / writer 2 is installed. The setting of the area information may be performed from an external device, for example, via the external communication unit 9, or the reader / writer 2 may be provided with a user interface for inputting area information. .

  Note that the communication control unit 7, the position measurement unit 8, the area determination unit 10, and the external communication unit 9 included in the reader / writer 2 may be configured by hardware logic. (Read Only Memory) or a configuration realized by executing a program stored in a storage unit such as a RAM.

  When each of the above-described configurations is configured by calculation means such as a CPU and storage means, a computer having these means reads the recording medium on which the program is recorded, and executes the program, whereby the communication control unit 7, position Various functions and various processes of the measurement unit 8, the area determination unit 10, and the external communication unit 9 can be realized. In addition, by recording the program on a removable recording medium, the various functions and various processes described above can be realized on an arbitrary computer.

  As this recording medium, a program medium such as a memory (not shown) such as ROM may be used for processing by a computer, and a program reader is provided as an external storage device (not shown). The program medium may be readable by inserting a recording medium therein.

  In any case, the stored program is preferably configured to be accessed and executed by the microprocessor. Furthermore, it is preferable that the program is read out, and the read program is downloaded to a program storage area of the microcomputer and the program is executed. It is assumed that this download program is stored in advance in the main unit.

  In addition, if the system configuration is capable of connecting to a communication network including the Internet, the recording medium is preferably a recording medium that fluidly carries the program so as to download the program from the communication network.

  Further, when the program is downloaded from the communication network as described above, it is preferable that the download program is stored in the main device in advance or installed from another recording medium.

(Configuration for distance measurement)
Next, a configuration for measuring the distance between the RFID tag 1 and the reader / writer 2 in the reader / writer 2 will be described with reference to FIG. As shown in the figure, the transmission processing unit 5 includes a PLL (Phase Locked Loop) unit 5A as a frequency adjustment unit, a modulation unit 5B, a power amplification unit 5C, and a transmitter 5D. The reception processing unit 6 includes an amplification unit 6A and a frequency conversion unit 6B. The position measurement unit 8 includes a phase information acquisition unit 8A and a distance calculation unit 8B. The communication control unit 7 includes a frequency control unit 7A, a transmission control unit 7B, and a reception control unit 7C.

  In the transmission processing unit 5, the PLL unit 5A sets a carrier frequency of a transmission signal transmitted from the transmission antenna 3, and is configured by a PLL circuit. The modulation unit 5B performs a process of modulating the carrier signal generated by the PLL unit 5A and the transmitter 5D and superimposing data on the transmission signal. In the present embodiment, the modulation unit 5B generates a transmission signal by ASK (Amplitude Shift Keying) modulation. Note that the transmission signal modulation method is not limited to the above-described ASK modulation, and other digital modulation methods such as FSK (Frequency Shift Keying) modulation and PSK (Phase Shift Keying) modulation may be adopted. . The power amplifier 5C amplifies the transmission signal.

  In the reception processing unit 6, the amplification unit 6 </ b> A amplifies the reception signal received by the reception antenna 4. The frequency conversion unit 6B performs a process of converting the frequency of the reception signal amplified by the amplification unit 6A and converting it to a lower frequency signal.

  In the position measurement unit 8, the phase information acquisition unit 8A detects the amount of change in the phase of the reception signal frequency-converted by the frequency conversion unit 6B, and acquires this as phase information. Note that the amount of change in phase of the received signal indicates the amount of change in phase that occurs when the received signal propagates a predetermined distance.

More specifically, assuming that the carrier signal output from the PLL unit 5A is sin2πf ₁ t, the frequency converter 6B receives the carrier signal sin2πf ₁ t and the received signal D (t) Asin (2πf ₁ t input from the amplifier 6A. The value (D (t) Acosφ) obtained by multiplying + φ) is sent to the phase information acquisition unit 8A. The phase information acquisition unit 8A calculates the phase change amount φ based on the value sent from the frequency conversion unit 6B. Here, t is time, D (t) is a baseband signal when ASK modulation is performed in the modulation unit 5B, A is the amplitude of the carrier signal itself, and φ is a phase change caused by propagating a distance of 2r round-trip. Each amount is shown.

  The distance calculation unit 8B calculates the distance between the corresponding RFID tag 1 and the reader / writer 2 based on the phase change amount information acquired by the phase information acquisition unit 8A. Details of this distance calculation method will be described later.

  In the communication control unit 7, the frequency control unit 7A controls the frequency of the carrier signal set by the PLL unit 5A. The transmission control unit 7B inputs data for modulating the transmission signal to the modulation unit 5B. The reception control unit 7C performs processing in which the communication control unit 7 receives the distance information calculated by the distance calculation unit 8B.

(Details of distance measurement)
Next, details of the distance measurement process will be described. In the present embodiment, the reader / writer 2 transmits an R / W request signal (request signal) to the RFID tag 1, and the RFID tag 1 returns a response signal (reflection signal) accordingly. Yes. This is shown in FIGS. 3 (a) to 3 (c). FIG. 3A is a diagram illustrating a state in which an R / W request signal and a response signal are transmitted and received between the reader / writer and the RFID tag. FIG. 3B shows a signal transmitted from the reader / writer to the RFID tag and its carrier frequency on the time axis. FIG. 3C is a diagram showing a signal transmitted from the RFID tag to the reader / writer and its carrier frequency on a time axis.

  The reader / writer 2 always transmits a specific signal (a signal for supplying power to the RFID tag 1), while transmitting a response signal (hereinafter referred to as a tag response signal) to the RFID tag 1. When requesting this, as shown in FIG. 3B, an R / W request signal for requesting a reply of the tag response signal is transmitted. That is, the transmission control unit 7B in the reader / writer 2 controls the modulation unit 5B to transmit data indicating the steady state in the steady state, and configures the R / W request signal when requesting the tag response signal. The modulation unit 5B is controlled to transmit data. The RFID tag 1 constantly monitors the signal sent from the reader / writer 2 and, when detecting that the R / W request signal has been received, transmits the tag response signal in response to the signal.

More specifically, the reader / writer 2 transmits a signal of one frame composed of an R / W request signal and CW (continuous carrier wave). RFID tag 1 transmits from the reader-writer 2 receives the R / W request signal and CW (continuous carrier wave), CW a tag response signal consisting of a carrier frequency f ₁ corresponding to the frequency (continuous carrier wave) to the reader writer 2 . 3B and 3C, the R / W request signal and the CW (continuous carrier wave) are transmitted by the carrier frequency f ₁ , and the tag response signal is transmitted by the carrier frequency f ₁ accordingly. .

  As shown in FIG. 3C, the tag response signal is composed of a frame having a preamble part and a data part. The preamble portion indicates data indicating the start of a tag response signal, and is predetermined data common to all RFID tags 1 within the same standard (for example, EPC). The data part is transmitted subsequent to the preamble part, and indicates data indicating substantial information transmitted from the RFID tag 1. Examples of the information included in the data part include ID information unique to each RFID tag 1. Information to be transmitted from the RFID tag 1, for example, various information stored in the storage part in the RFID tag 1. Etc. may be included.

The reader / writer 2 transmits the R / W request signal twice and sets the carrier frequencies in the transmission of each R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal) to each other. It is different. That is, the frequency controller 7A of the reader writer 2, when transmitting the first R / W request signal, and controls the PLL section 5A to output the carrier signal at a first frequency f _1, 2 nd R / When transmitting the W request signal, the PLL unit 5A is controlled so as to output the carrier signal at the second frequency f ₂ different from the _first frequency f ₁ .

As shown in FIGS. 1 and 3, when the first R / W request signal transmitted at the frequency f ₁ RFID tag 1 receives the tag response signal is returned again in the first frequency f _1. Then, the reader-writer 2, by analyzing the preamble portion of the tag response signal phase information acquiring section 8A receives, detects the phi ₁ that indicates the phase change amount of the tag response signal. Similarly, when the second R / W request signal transmitted at the frequency f ₂ RFID tag 1 receives the tag response signal is returned again at the second frequency f _2. Then, the reader-writer 2, by analyzing the preamble portion of the tag response signal phase information acquiring section 8A receives, detects the phi ₂ showing the phase change amount of the tag response signal. The analysis described here is processing for detecting the amount of change in the phase of the tag response signal.

  In the above example, the amount of change in the phase of the tag response signal is detected by analyzing the preamble part. However, the present invention is not limited to this, and the phase change including the data part is also included. The amount of change may be detected, or the amount of phase change may be detected in the data portion. However, when the modulation method is PSK, it is difficult to detect the amount of change in phase with distance based on the data part whose contents can change. Therefore, in the preamble part whose contents are fixed, It is preferable to detect the amount of change. A specific example of analyzing the preamble part or the data part will be described later.

As described above, when the phase information acquiring unit 8A detects a change amount phi ₁ and phi ₂ of the phase information of the amount of change in the phase is transmitted to the distance calculation section 8B. Distance calculator 8B based on the phi ₁ and phi _2, is calculated as follows distance between the RFID tag 1 and the reader-writer 2.

First, it is assumed that the distance from the transmitting antenna 3 to the RFID tag 1 and the distance from the receiving antenna 4 to the RFID tag 1 are equal, and this is set as a distance r. Phase change amounts φ ₁ and φ ₂ caused by propagation of a signal carried by the first frequency f ₁ and the second frequency f ₂ through the distance of the round trip 2r are expressed by the following equations.

In the above formula, c represents the speed of light. Based on the above two formulas, the distance r is obtained by the following formula.

As described above, the distance r from the transmission antenna 3 to the RFID tag 1 can be obtained based on the phase change amounts φ ₁ and φ ₂ . Note that, in the RFID tag 1, it is expected that a phase shift will occur between the reception of the R / W request signal and the transmission of the tag response signal. This phase shift is caused by the first frequency f _1. and it becomes even the same amount in both of the signal carried by the second frequency f _2. Therefore, a phase shift that occurs during signal transmission / reception in the RFID tag 1 does not affect the calculation of the distance.

In Equation 2, when φ ₂ is 2π or more, the distance r cannot be calculated accurately. That is, the maximum value rmax of the distance r that can be measured is when Δφ = 2π, and is represented by the following equation.

Here, for example, when the difference between the first frequency f ₁ and the second frequency f ₂ is 5 MHz, the maximum distance rmax is 30 m from Equation 3. Similarly, when the difference between the first frequency f ₁ and the second frequency f ₂ is 2 MHz, the maximum distance rmax is 75 m from Equation 3. In the RFID communication system using the UHF band, since the assumed maximum communication distance is about 10 m, it can be understood that the above measurement has no practical problem.

  Even when the measurement of the maximum distance rmax or more is necessary, it is possible to measure the distance r by using, for example, measurement of the reception intensity of the received signal. Specifically, when Δφ may be 2π or more, the candidate r ′ for the distance r is r ′ = r + n · rmax (n is an integer of 0 or more). Therefore, it is possible to specify the value of n by using the fact that the reception intensity of the reception signal decreases as the distance r increases.

  When an active type RFID tag is used, the distance is measured based on the tag response signal actively sent from the RFID tag side without sending the R / W request signal from the reader / writer 2 side. It may be like this.

(Specific example of the reception processing unit)
In the distance measurement described above, processing for detecting the amount of change in the phase of the received signal is performed. Regarding the specific configuration of the reception processing unit 6 that enables detection of the amount of change in phase, This will be described below with reference to FIG. In this specific example, the reception processing unit 6 separates the received signal into an I signal and a Q signal and inputs the signals to the position measurement unit 8, thereby enabling the phase measurement amount detection processing in the position measurement unit 8. It has become a thing. As shown in the figure, the reception processing unit 6 includes two amplification units 6A1 and 6A2 as amplification units 6A, mixers 6B1 and 6B2 as frequency conversion units 6B, and a 90 ° phase shift unit 6B3.

  A reception signal received by the reception antenna 4 is branched into two paths, one of which is input to the amplification unit 6A1 and the other is input to the amplification unit 6A2. The amplifying unit 6A1 amplifies the input received signal and inputs it to the mixer 6B1. The amplifying unit 6A2 amplifies the input received signal and inputs it to the mixer 6B2.

  The mixer 6B1 outputs an I signal by multiplying the reception signal input from the amplification unit 6A1 and the carrier signal output from the PLL unit 5A, and inputs this I signal to the phase information acquisition unit 8A. The mixer 6B2 multiplies the reception signal input from the amplification unit 6A2 and the carrier signal output from the PLL unit 5A and whose phase has been changed by 90 ° through the 90 ° phase shift unit 6B3, thereby multiplying the Q signal. The Q signal is output to the phase information acquisition unit 8A.

  Details of the reception process and the distance r calculation process performed in the above configuration will be described below.

Signal received distance propagated in the reader writer 2 of reciprocating 2r, when the frequency of the carrier signal f _1, is expressed by the following equation.

In the above equation, t is time, s ₁ (t) is the state of the signal transmitted by the carrier signal of frequency f ₁ , D (t) is the baseband signal when ASK modulation is performed in the modulator 5B, A Represents the amplitude of the carrier signal itself, and φ ₁ represents the amount of change in phase due to propagation through the distance of 2r round-trip. In this case, I ₁ (t) indicating the state of the I signal output by the mixer 6B1 and Q ₁ (t) indicating the state of the Q signal output by the mixer 6Bl are expressed by the following equations.

From the above, based on the I signal and the Q signal, the signal phase change φ ₁ due to the carrier signal having the frequency f ₁ can be obtained by the following equation.

Similarly, the amount of signal phase change φ ₂ due to the carrier signal of frequency f ₂ can be obtained by the following equation.

As described above, the phase information acquiring section 8A based on the input I and Q signals, to obtain the change amounts phi ₁ and phi ₂ phases. Then, the distance calculation unit 8B calculates the distance r by the following formula.

(Distance measurement process flow)
Next, the flow of the distance measurement process in the reader / writer 2 will be described with reference to the flowchart shown in FIG.

First, when the distance measurement process is started, in step 1 (hereinafter referred to as S1), the frequency controller 7A sets the frequency of the carrier signal when transmitting the R / W request signal to the first frequency f. _The PLL unit 5A is controlled to be ₁ .

Next, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. Then, the transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S2). When the R / W request signal is transmitted, CW (continuous carrier wave) is subsequently transmitted at the first frequency f ₁ (S3).

When the RFID tag 1 detects the R / W request signal, it subsequently returns a tag response signal having a carrier frequency corresponding to the first frequency f ₁ of the detected CW (continuous carrier wave). The reception antenna 4 receives this tag response signal, the reception processing unit 6 performs reception processing (S4), and the phase information acquisition unit 8A performs phase information acquisition processing (S5).

That is, in the reception processing unit 6, the frequency conversion unit 6B multiplies the reception signal input from the amplification unit 6A and the carrier signal output from the PLL unit 5A based on the mathematical formulas 4 to 6 described above. To obtain the I signal and the Q signal. When the phase information acquisition unit 8A receives the I signal and the Q signal from the frequency conversion unit 6B, the phase information acquisition unit 8A calculates the phase change amount φ ₁ of the first frequency f ₁ on the basis of the mathematical expression 7 described above, and the carrier signal Is stored in the table in correspondence with the frequency used as (first frequency f ₁ ).

When the reception processing unit 6 finishes receiving the tag response signal from the RFID tag 1 (S6), the phase information acquisition unit 8A ends the phase information acquisition process (S7). Thereafter, the transmission processing unit 5 ends the transmission of CW (continuous carrier wave), that is, the transmission of a signal consisting of one frame (S8). The reception control unit 7C determines whether or not reception signals of all frequencies to be received have been received. If it is determined that all reception signals have not been received (NO in S9), the process returns to the process from S1. Here, in the above example, since the first frequency f ₁ and the second frequency f ₂ are assumed as the frequencies of the reception signal, the reception control unit 7C has the first frequency f ₁ and the second frequency f 2. It is determined whether or not both received signals of the frequency f ₂ are received.

Since this point has received only the first reception signal of the frequency f _1, so that the processing from Sl is performed. Then, in the processing of the second S1, so that the frequency controller 7A becomes a carrier signal (and CW (continuous carrier wave)) frequency f ₂ to the frequency of the second of the occasion of transmitting the R / W request signal PLL Control part 5A. Then, the second frequency f _2, as well as with respect to the first frequency f _1, the process of S2~S8 is performed, it is determined that it has received the reception signals of all frequencies to be received at (S9 YES), the process proceeds to S10.

  In S10, based on the acquired phase information, the distance calculation unit 8B calculates the distance between the RFID tag 1 and the reader / writer 2 by the method described above. More specifically, the distance calculation unit 8B extracts the amount of phase change for each frequency from the table, and calculates the distance r based on the above mathematical formula 9. The calculated distance information is transmitted to the reception control unit 7C. Thus, the distance measurement process is completed.

Here, the process of analyzing the phase information performed by the phase information acquisition unit 8A in step S5 will be described by taking a specific process after obtaining the I signal and the Q signal as an example. First, it is assumed that the tag response signal is a signal for transmitting a digital signal composed of “0” and “1”. Further, it is assumed that the frequencies of “0” and “1” in the tag response signal are different, that is, the periods of “0” and “1” are different. The phase information acquisition unit 8A performs Fourier transform on the I signal received from the frequency conversion unit 6B. By performing the Fourier transform, for example, peaks appear at the positions of the frequency of “0” and the frequency of “1” constituting the tag response signal. Similarly, when the phase information acquisition unit 8A performs Fourier transform on the Q signal received from the frequency conversion unit 6B, peaks appear at the respective frequency positions of “0” and “1”. The height of the peak appearing at the frequency position of “0” is proportional to the number of “0” in the tag response signal, and the height of the peak appearing at the frequency position of “1” is “ It is proportional to the number of “1”. The peak height of “1” (and “0”) obtained from the I signal is proportional to I ₁ (t), and “1” (and “0”) obtained from the Q signal. The height of the peak is proportional to Q ₁ (t). Therefore, the phase information acquiring section 8A is the height of the peak of the "1" obtained from the I signal, the height of the peak of the "1" obtained from the Q signal, respectively, I ₁ number 7 described above By substituting for (t) and Q ₁ (t), φ ₁ can be calculated. Then, the calculated φ ₁ is stored in a table in correspondence with the frequency (first frequency f ₁ ) used as the carrier signal. At this time, instead of the height of the peak of “1”, the height of the peak of “0” obtained from the I signal and the height of the peak of “0” obtained from the Q signal may be used. Good. Note that the peak of “0” or “1” obtained by the Fourier transform due to the fluctuation of the frequency of “0” or “1” or the occurrence of an error due to the transmission state of the tag response signal or the like is “0”. ”And“ 1 ”are often scattered in the vicinity of the frequency, and usually, a peak in the vicinity of the frequency of“ 0 ”and“ 1 ”is detected from the result obtained by Fourier transform. The obtained peak is defined as a peak of “0” or “1” obtained by Fourier transform.

Here, when the frequencies of “0” and “1” in the tag response signal are different as described above, either one of “0” and “1” is obtained from the result obtained by Fourier transform. Although it is necessary to detect the peak, the content of the data included in the data part of the tag response signal changes, so the number of either “0” or “1” is extremely small, and the peak is sufficient. May not be detected. For this reason, when obtaining the peak height from the result obtained by Fourier transform of the data portion, it is necessary to first detect the peak near both the frequency of “0” and the frequency of “1”. It takes a long time, and there is a risk of inconvenience when processing close to real time is performed. On the other hand, if the preamble part in the frame is within the same standard, the content of the data is fixed, so the number of “0” and “1” can be known in advance. For this reason, if it is determined in advance that a peak having a larger number of “0” and “1” among peaks obtained by Fourier transform is to be detected, the determined “0” or “1” is determined. It is only necessary to detect a peak only in the vicinity of the frequency, and the peak detection process can be shortened compared to the case of detecting the peak from the result obtained by Fourier transforming the data portion. For this reason, it is preferable to calculate φ ₁ by analyzing the preamble portion as described above in order to perform the phase information acquisition process at high speed.

If the frequency of “0” and the frequency of “1” constituting the tag response signal are the same, the peak obtained by performing the Fourier transform is one, and the height is “ The phase information acquisition unit 8A has a peak height of “0” and “1” obtained from the I signal and “0” obtained from the Q signal. ”And“ 1 ”peaks can be substituted for I ₁ (t) and Q ₁ (t) in Equation ₇ to obtain φ ₁ .

Such processing is the same when obtaining φ ₂ .

  Further, the phase information acquisition process performed by the phase information acquisition unit 8A may be a process other than the above.

(Distance measurement using multiple frequencies)
In the above example, the distance is measured by receiving reception signals of two different frequencies. However, as shown below, the configuration is such that reception signals of three or more different frequencies are received. Also good.

  When signals are transmitted and received between the reader / writer 2 and the RFID tag 1, basically, the signal transmitted from the reader / writer 2 directly reaches the RFID tag 1, and the signal transmitted from the RFID tag 1 directly The reader / writer 2 is reached. However, it is conceivable that a signal does not directly reach between the reader / writer 2 and the RFID tag 1 but arrives after being reflected by some surrounding object (multipath). In this case, the received signal received by the reader / writer 2 may be affected by multipath, and noise may be mixed with the original phase state, resulting in degradation of S / N. That is, in the method for calculating the distance based on the phase, the accuracy of the obtained phase information is deteriorated, so that the accuracy of the calculated distance is also deteriorated.

  Also, in the above example, the method of separating the received signal into the I signal and the Q signal and detecting the amount of phase change based on these is shown. However, depending on the phase state, either the I signal or the Q signal is shown. Can be significantly smaller. In this case, the influence of the measurement error of the signal that is remarkably small greatly affects the calculation of the phase. That is, when either the I signal or the Q signal is remarkably small, the error in the measured phase increases and the accuracy of the calculated distance also deteriorates.

  Therefore, the above-described problem can be solved by performing the following processing. That is, first, the reader / writer 2 transmits three or more R / W request signals having different frequencies and receives a tag response signal for each. Then, two received signals having higher S / N and higher I / Q signal levels are selected from the received signals, and the phase change amount is detected based on the two received signals selected. And position calculation.

(Flow of distance measurement processing using multiple frequencies)
Next, the flow of the distance measurement process using the multiple frequencies in the reader / writer 2 will be described with reference to the flowchart shown in FIG.

First, when the distance measurement processing is started, in S11, the frequency controller 7A is controlled PLL section 5A so that frequency of the carrier signal as a first frequency f ₁ at the time of transmitting the R / W request signal To do.

Next, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. Then, the transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S12). When the R / W request signal is transmitted, CW (continuous carrier wave) is then transmitted at the first frequency f ₁ (S13).

  When the RFID tag 1 detects the R / W request signal, it subsequently returns a tag response signal having a carrier frequency corresponding to the first frequency f1 of the detected CW (continuous carrier wave). The tag response signal is received by the reception antenna 4, the reception processing unit 6 performs reception processing (Sl4), and the phase information acquisition unit 8A performs phase information acquisition processing (S15).

That is, in the reception processing unit 6, the frequency conversion unit 6B multiplies the reception signal input from the amplification unit 6A and the carrier signal output from the PLL unit 5A based on the above mathematical expressions 4 to 6. Thus, the I signal and the Q signal are obtained. When the phase information acquisition unit 8A receives the I signal and the Q signal from the frequency conversion unit 6B, the phase information acquisition unit 8A calculates the phase change amounts φ ₁ and φ ₂ of the first frequency f ₁ based on the mathematical expressions 7 to 8 described above. In addition to the calculation, the signal level s (t) is obtained based on the following equation (10). Then, the phase information acquisition unit 8A stores the obtained phase change amount and signal level in a table in association with the frequency (first frequency f ₁ ) used as the carrier signal.

  When the reception processing unit 6 finishes receiving the tag response signal from the RFID tag 1 (S16), the phase information acquisition unit 8A ends the phase information acquisition process (S17). Thereafter, the transmission processing unit 5 ends the transmission of CW (continuous carrier wave), that is, the transmission of a signal consisting of one frame (S18). Thereafter, the reception control unit 7C determines whether or not reception signals of all frequencies to be received have been received (S19), and if it is determined that all signals have not been received, the process returns to the process from S11. Here, assuming that the first to fourth frequencies are set as the frequencies of the reception signals, the reception control unit 7C determines whether or not all the reception signals of the first to fourth frequencies have been received. It will be judged.

  In S20, a frequency selection process by the phase information acquisition unit 8A and a distance calculation process by the distance calculation unit 8B are performed, and the distance measurement process ends.

  Next, the flow of the frequency selection process by the phase information acquisition unit 8A and the distance calculation process by the distance calculation unit 8B in S20 will be described with reference to the flowchart shown in FIG.

  First, in S21, the phase information acquisition unit 8A acquires signal levels of received signals of all frequencies received from the table.

  Next, in S22, the phase information acquisition unit 8A determines whether or not the signal level of the reception signal at each frequency exceeds a predetermined threshold value. This predetermined threshold value is set in advance as a minimum value at which sufficient accuracy can be obtained in distance calculation. Then, the phase information acquisition unit 8A determines whether the number of frequencies of the received signal that exceeds the predetermined threshold is less than 2, greater than 2, or 2.

  If it is determined that the number of frequencies of the received signal exceeding the predetermined threshold is less than 2, in S23, the phase information acquisition unit 8A re-acquires the received signal with other frequencies. Instructs the communication control unit 7 to transmit an R / W request signal at another frequency.

  On the other hand, if it is determined that the number of frequencies of the received signal exceeding the predetermined threshold is greater than 2, first, in S24, the phase information acquisition unit 8A determines that the frequency of the received signal does not exceed the predetermined threshold. Is removed from the selection candidates. Then, in S25, the phase information acquisition unit 8A extracts, as a minimum component, a component having a smaller signal level from among the I signal and the Q signal for each of the frequencies of the reception signal remaining as selection candidates. Thereafter, in S25, the phase information acquisition unit 8A selects two of the minimum components of each frequency from the one with the higher signal level. For a received signal having a frequency corresponding to the two selected minimum components, the phase information acquisition unit 8A acquires phase information from the table and transmits it to the distance calculation unit 8B. In S27, the distance calculation unit 8B performs a distance calculation process based on the received phase information.

  On the other hand, when it is determined that the number of received signals exceeding the predetermined threshold is 2, the phase information acquiring unit 8A acquires phase information regarding the two received signals, and this is calculated as a distance calculating unit. Transmit to 8B. In S27, the distance calculation unit 8B performs a distance calculation process based on the received phase information.

FIG. 8 schematically shows an example of the frequency selection process. In this example, it is assumed that a reception signal having a frequency of f _{1 to} f ₄ is received. The I signal component in the received signal at frequency f ₁ is I ₁ , the Q signal component is Q ₁ , and the received signal level is S ₁ , the I signal component in the received signal at frequency f ₂ is I ₂ , the Q signal component is Q ₂ , and the received signal level and S _2, the I signal component in the received signal frequency f3 I _3, Q signal component Q _3, and the received signal level and S _3, the I signal component in the received signal frequency f ₄ I ₄ , the Q signal component is Q ₄ , and the received signal level is S 4.

First, in S22 in the above, among the S1~S4 signal level, S2 is equal to or less than a predetermined threshold value, the processing of S24, the received signal of frequency f ₂ is removed from the selection candidates. Next, as a minimum component, the frequency f ₁ is selected as Q ₁ , the frequency f ₃ is selected as I ₃ , and the frequency f ₄ is selected as Q ₄ by the processing of S 25. Then, by the processing of S25, _Q, of the I 3, _{Q 4,} by which the signal level is selected is greater than _Q 1, _{I 3,} the received signal of frequency _{f 1} and frequency _{f 3} is selected.

  As a result of the above processing, one of the received signals having the S / N deteriorated due to the influence of the multipath, the I signal and the Q signal is remarkably reduced. It is possible to select the received signal by eliminating the received signal. As a result, the accuracy of distance calculation can be kept high in any situation.

(Distance calculation method using MUSIC method)
Next, another example of the distance calculation method will be described. In the above example, the amount of change in the phase of the received signal at two frequencies is detected, and based on these, the distance r is calculated by the above equation (9). On the other hand, as shown below, the distance r can be calculated by applying the concept of the MUSIC (Multiple Signal Classification) method, which is one of the high resolution spectrum analysis methods.

Conventionally, the MUSIC method is widely known as a method for estimating the arrival direction of radio waves. In this MUSIC method, the direction of arrival of radio waves is estimated by analyzing received signals received by a plurality of antenna elements. In this MUSIC method, the received signal from each antenna element in the direction of arrival estimation is replaced with the received signal of each frequency described above, and an applied model in MUSIC method (mode vector a (θ _i ) used in direction of arrival estimation) The distance r can be estimated by changing the equation 11) to the mode vector a (r _i ) (the following equation 12) used in the distance estimation. In this way, by applying the MUSIC method in the estimation of the distance r, as shown below, it becomes possible to further reduce the influence of multipath under a certain real environment such as the occurrence of multipath, and further improve the accuracy. Can be increased.

That is, if the number of elements of the array antenna is K, the wavelength of the incoming wave is λ, the number of incoming waves is L, and the arrival angle of the i-th incoming wave is θ _i (i = 1... L), The vector a (θi) is a (θ _i ) = [exp {jΦ ₁ (θ _i )}, ..., exp {jΦ _K (θ _i )}] ^T ; Φ _N (θ _i ) =-(2π / λ) d _N sin (θ _i ) (Φ _N (θ _i ) is the reception phase of the i-th wave in the N-th antenna element, ^T is transposed, and d _N is the N-th antenna element position) (Equation 11).

In Equation 11, K: The number of frequencies using the number of elements of the array antenna (f ₁ , f ₂ , f ₃ ... F _K ), and the arrival angle θ _i of the i-th incoming wave up to the i-th tag the distance _{r i (r 1 ... r L} ), the array response vector a _{(r i)} for array response vector a with respect to the i-th arrival wave (theta _i) the i-th tag, the N-th antenna element reception phase ΦN of the signal reception phase ΦN of the i wave (theta _i) from the i-th tag in the N-th frequency in the _{(r i) (Φ N (} r i) = - 2πf N · 2r i / c and (c: speed of light (3 × 108))) are respectively substituted, and the mode vector a (r _i ) (Equation 12) is derived (see FIG. 9C).

  Details of distance measurement processing (referred to as distance estimation MUSIC method) applying the MUSIC method will be described below. The distance measurement process described below is performed in the position measurement unit 8.

In the received signal of frequency f ₁ , I ₁ (t) indicating the state of the I signal and Q ₁ (t) indicating the state of the Q signal are expressed by the above-described Expression 5 and Expression 6. Here, x ₁ (t) representing the received signal of frequency f _{1 in} a complex expression is represented by the following equation.

Similarly, x _N (t) representing the reception signal of frequency f _{N in} a complex expression is represented by the following expression.

Here, considering the case where received signals are received at K frequencies, a correlation matrix R _xx shown below is generated based on received signals of frequencies f _{1 to} f _K.

In the above formula, H represents a complex conjugate transpose, and E [] represents a time average. Next, eigenvalue decomposition of the correlation matrix R _xx obtained above is performed as follows.

In the above equation, e _i is an eigenvector of R _xx , μ _i is an eigenvalue, and σ ² is noise power. From these, the following relationship holds.

From the above, the mode vector and the MUSIC evaluation function P _MUSIC in the distance estimation MUSIC method are given as follows.

In the above equation, a graph as shown in FIG. 9B is obtained by changing r. In this graph, the horizontal axis is r, and the vertical axis is _PMUSIC . As shown in this graph, a peak occurs in the evaluation function P _MUSIC , and the value of r where the peak occurs corresponds to the distance r to be calculated.

In the graph shown in FIG. 9B, the peak of the evaluation function P _MUSIC appears only at one place, but the peak may appear at other places. This is because, as shown in FIG. 9A, when affected by a multipath, a peak appears at a distance corresponding to the multipath. However, since the distance corresponding to the multipath is longer than the distance r to be calculated, the multipath is generated by setting the smallest r among the distances where the peaks are generated as the distance r to be calculated. Also, the distance r can be accurately calculated.

  In the above example, the MUSIC method as a high-resolution spectrum analysis method is applied to distance measurement, but other high-resolution spectrum analysis methods such as Beamformer method, Capon method, LP (Linear Prediction) method, Min -Norm method and ESPRIT method may be applied to distance measurement.

(Flow of distance measurement process using MUSIC method)
Next, the flow of distance measurement processing using the above MUSIC method in the reader / writer 2 will be described with reference to the flowcharts shown in FIGS. 10 and 11.

First, when the distance measurement processing is started, in S31, the frequency controller 7A is controlled PLL section 5A so that frequency of the carrier signal as a first frequency f ₁ at the time of transmitting the R / W request signal To do.

Next, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. The transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S32). When the R / W request signal is transmitted, CW (continuous carrier wave) is then transmitted at the first frequency f ₁ (S33).

When the RFID tag 1 detects the R / W request signal, it subsequently returns a tag response signal having a carrier frequency corresponding to the first frequency f ₁ of the detected CW (continuous carrier wave). The reception antenna 4 receives this tag response signal, the reception processing unit 6 performs reception processing (S34), and the phase information acquisition unit 8A performs phase information acquisition processing (S35).

That is, in the reception processing unit 6, the frequency conversion unit 6B multiplies the reception signal input from the amplification unit 6A and the carrier signal output from the PLL unit 5A based on the above mathematical expressions 4 to 6. Thus, the I signal and the Q signal are obtained. When the phase information acquisition unit 8A receives the I signal and the Q signal from the frequency conversion unit 6B, the phase information acquisition unit 8A x ₁ that represents the reception signal of the first frequency f _{1 in} a complex expression based on the above mathematical expressions 13 to 14. (T) is calculated and stored in the table in correspondence with the frequency (first frequency f ₁ ) used as the carrier signal.

  When the reception processing unit 6 finishes receiving the tag response signal from the RFID tag 1 (S36), the phase information acquisition unit 8A ends the phase information acquisition process (S37). Thereafter, the transmission processing unit 5 ends the transmission of CW (continuous carrier wave), that is, the transmission of a signal consisting of one frame (S38). Thereafter, the reception control unit 7C determines whether or not reception signals of all frequencies to be received have been received. If it is determined that all signals have not been received, the process returns to S31. Here, if the first to Nth frequencies are set as the frequencies of the reception signals, the reception control unit 7C determines whether or not all the reception signals of the first to Nth frequencies have been received. It will be judged.

At this point, since the received only the first reception signal of the frequency f _1, so that the processing from S31 is performed. Then, in the processing of S31 in the second, so that the frequency controller 7A becomes a carrier signal (and CW (continuous carrier wave)) frequency _{f 2} to the frequency of the second of the occasion of transmitting the R / W request signal PLL Control part 5A. Thereafter, the processing of S32 to S38 is performed, and this is repeated until reception of all the received signals of the Nth frequency is confirmed. If it is determined in S39 that reception signals of all frequencies to be received have been received, the process proceeds to S40.

In S40, the position measurement unit 8 reads the reception signal x _n (t) of each frequency from the table, and creates a correlation matrix R _xx based on the reception signal of each frequency. Next, the position measurement unit 8 performs eigenvalue decomposition of the correlation matrix _Rxx , decomposes noise components (S41), and creates a spectrum of the MUSIC evaluation function P _MUSIC , thereby searching for a peak value (S42). . Thereby, the distance r is calculated in S43.

(Frequency switching within one frame)
In the above, the reader / writer 2 transmits the R / W request signal a plurality of times, and changes the carrier frequency in each transmission, thereby receiving tag response signals having different carrier signal frequencies. On the other hand, by changing the carrier frequency at least once in the middle of transmitting the R / W request signal and CW (continuous carrier wave) consisting of one frame, it consists of one frame in which the carrier frequency changes at least once in the middle. The tag response signal can be received and the distance can be measured based on the tag response signal.

As shown in FIG. 12 (a), the reader / writer 2 always transmits a specific signal, while returning a tag response signal when requesting the RFID tag 1 to transmit a tag response signal. The requested R / W request signal is transmitted. Here, the frequency control unit 7A sets a plurality of divided periods within a period in which an R / W request signal (more specifically, a CW (continuous carrier wave) following the R / W request signal) is transmitted, and in each divided period, The PLL unit 5A is controlled so that the carrier frequencies are different from each other. In the example shown in FIG. 12A, three division periods are set, and the frequency f ₁ is set in the first division period, the frequency f _{2 is set} in the _second division period, and the frequency f ₃ is set in the third division period. Control is done.

The RFID tag 1 constantly monitors the signal sent from the reader / writer 2 and, when detecting that the R / W request signal has been received, transmits the tag response signal in response to the signal. Here, the carrier frequency of the tag response signal changes according to the time change of the carrier frequency in the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal). In the example shown in FIG. 12B, the frequency f ₁ is in the first period of the tag response signal, the frequency f _{2 is} in the _second period, and the frequency f ₃ is in the third period.

  By receiving such a tag response signal, the position measuring unit 8 can detect the state of the received signal at a plurality of different frequencies. The timing of the frequency conversion process of the tag response signal in the reception processing unit 6 is based on the frequency switching timing at the time of transmitting the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal). Is set.

  Here, in the tag response signal, the period during which the carrier frequency is switched is preferably within the period of the preamble portion. This is because, in the tag response signal, the length of the data portion varies while the length of the preamble portion is fixed, so that a period during which the carrier frequency is switched can be ensured.

(Distance measurement process flow with frequency switching within one frame)
Next, the flow of distance measurement processing that involves frequency switching in the above-described one frame in the reader / writer 2 will be described with reference to the flowchart shown in FIG.

  First, when the distance measurement process is started, the frequency control unit 7A sets the frequency of the carrier signal (more specifically, the CW (continuous carrier wave) following the R / W request signal) when transmitting the R / W request signal. The PLL unit 5A is controlled so as to be switched for each of the plurality of divided periods. Then, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. Then, the transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S51). When the R / W request signal is transmitted, CW (continuous carrier wave) is transmitted at a different frequency for each of the plurality of divided periods (S53, S55, S58). Thereby, the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal) whose frequency is switched for each divided period is transmitted.

When the RFID tag 1 detects the R / W request signal, followed by detecting CW carrier frequency (continuous carrier wave) (frequency _{f 1,} f 2, _{f 3)} of the carrier frequency changes according to the time variation (frequency _{f 1} , F ₂ , f ₃ ) is returned. The reception antenna 4 receives this tag response signal, the reception processing unit 6 performs reception processing (S53, S56, S59), and the phase information acquisition unit 8A performs phase information acquisition processing (S54, S57, S60). In the tag response signal received here, the carrier frequency changes according to the time change of the carrier frequency in the CW (continuous carrier wave) after the R / W request signal.

That is, in the reception processing unit 6, the frequency conversion unit 6B recognizes the preamble part in the tag response signal, and based on the above equations 4 to 6, the I signal and Q for the frequency of each divided period in the preamble part Find the signal. When the phase information acquisition unit 8A receives the I signal and the Q signal of each frequency from the frequency conversion unit 6B, the phase information acquisition unit 8A calculates the phase change amounts φ ₁ and φ ₂ of each frequency based on the above formulas 7 to 8. And stored in a table corresponding to the frequency used as the carrier signal. Here, the switching timing of each divided period is set based on the frequency switching timing at the time of transmitting the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal).

The frequency conversion and phase information acquisition processing for each frequency (frequency f ₁ , f ₂ , f ₃ ) in each divided period in the preamble portion of the tag response signal in the reception processing unit 6 and the phase information acquisition unit 8 A is performed in the transmission processing unit 5. This is performed while a CW (continuous carrier wave) having a corresponding frequency is being transmitted. For example, when the transmission processing unit 5 starts transmission of CW (continuous carrier wave) at the first frequency f ₁ (S52), the RFID tag 1 transmits the signal of the first division period in the preamble portion of the tag response signal to the first frequency to reply at a frequency _{f 1.} The reception processing unit 6 receives the tag response signal of the frequency f ₁ (S53), and the phase information acquisition unit 8A acquires the phase information of the frequency f ₁ (S54). After a certain period of time, the transmission processor 5 starts transmission of CW (continuous carrier wave) at the second frequency _{f 2} (S55). When receiving the CW (continuous carrier wave) of the second frequency f ₂ , the RFID tag 1 transmits a signal of the next divided period in the preamble portion of the tag response signal at the second frequency f ₂ . The reception processing unit 6 receives the tag response signal of the frequency f ₂ (S56), and the phase information acquisition unit 8A acquires the phase information of the frequency f ₂ (S57). After a certain period of time, then the transmission processing unit 5 with respect to the third frequency f _3, the reception processing section 6 and phase information acquiring section 8A repeats the same operation (S58 from S60).

  When the reception processing unit 6 finishes receiving the tag response signal from the RFID tag 1 (S61), the transmission processing unit 5 finishes transmission of CW (continuous carrier wave), that is, transmission of a signal consisting of one frame (62). . Thereafter, the distance calculation unit 8B calculates the distance r based on the phase information at a plurality of different frequencies stored in the table, and the process ends (S63).

  In the above example, the distance r is calculated based on the phase. However, the distance measurement process using the MUSIC method described above can be similarly applied. It is also possible to select two reception signals having higher I signal / Q signal levels and perform phase change detection and position calculation based on the two selected reception signals.

(Recognize the distance of each RFID tag)
As described above, the tag response signal includes the data portion. When the ID information unique to each RFID tag 1 is included in this data portion, the distance measured as described above by the tag response signal can be recognized in association with the RFID tag 1 that transmitted the tag response signal. It becomes possible. A configuration for realizing this will be described below with reference to FIG.

  The configuration shown in the figure is different from the configuration shown in FIG. 4 in that the reception processing unit 6 is provided with a preamble extraction unit 6C. The other configuration is the same as the configuration shown in FIG.

  The preamble extraction unit 6C receives the I signal and the Q signal output from the mixer 6B1 and the mixer 6B2, extracts the preamble portion in the tag response signal, transmits this to the position measurement unit 8, and transmits data in the tag response signal. Are transmitted as reception frames to the reception control unit 7C in the communication control unit 7. The position measuring unit 8 measures the distance as described above by analyzing the preamble part, and transmits the measured information to the reception control unit 7C.

  The reception controller 7C in the communication controller 7 recognizes the ID information of the RFID tag 1 that transmitted the tag response signal by analyzing the data part received from the preamble extractor 6C. In addition, the reception control unit 7C recognizes the distance measurement result of the RFID tag 1 measured by the position measurement unit 8 and the ID information. Thereby, even when there are a plurality of RFID tags 1 in the RFID tag communication system, the distances between the RFID tags 1 can be distinguished and recognized.

  Note that the information recognized in connection with the distance information is not limited to the ID information unique to each RFID tag 1, but may be any information as long as it is indicated by the data portion included in the tag response signal. Any information may be used.

(Flow of distance measurement processing that identifies each RFID tag)
Next, the flow of distance measurement processing for identifying each RFID tag in the reader / writer 2 will be described with reference to the flowchart shown in FIG.

First, when the distance measurement processing is started, in S71, the frequency controller 7A is controlled PLL section 5A so that frequency of the carrier signal as a first frequency f ₁ at the time of transmitting the R / W request signal To do.

Next, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. Then, the transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S72). When the R / W request signal is transmitted, CW (continuous carrier wave) is then transmitted at the first frequency f ₁ (S73).

When the RFID tag 1 detects the R / W request signal, it subsequently returns a tag response signal having a carrier frequency corresponding to the first frequency f ₁ of the detected CW (continuous carrier wave). The reception antenna 4 receives this tag response signal, the reception processing unit 6 performs reception processing (S74), and the phase information acquisition unit 8A performs phase information acquisition processing (S75).

That is, in the reception processing unit 6, the frequency conversion unit 6B multiplies the reception signal input from the amplification unit 6A and the carrier signal output from the PLL unit 5A based on the above mathematical expressions 4 to 6. Thus, the I signal and the Q signal are obtained. The preamble extraction unit 6C extracts the preamble part in the received tag response signal (I signal and Q signal) and transmits it to the position measurement unit 8, and transmits the data part in the tag response signal to the reception control unit 7C. . When the position measurement unit 8 receives the preamble from the preamble extraction unit 6C, the position measurement unit 8 calculates the phase change amounts φ ₁ and φ ₂ of the first frequency f ₁ based on the mathematical formulas 7 to 8 described above, The frequency is used as a signal (first frequency f ₁ ) and stored in a table (S75).

  When the reception processing unit 6 finishes receiving the tag response signal from the RFID tag 1 (S76), the position measurement 8 finishes the phase information acquisition process (S77). Thereafter, the transmission processing unit 5 ends the transmission of CW (continuous carrier wave) (S78). The reception control unit 7C determines whether or not reception signals of all frequencies to be received have been received, and when it is determined that all signals have not been received (NO in S79), the process returns to S71. On the other hand, when it is determined that reception signals of all frequencies to be received have been received (YES in S79), the process proceeds to S80.

  On the other hand, when receiving the data part from the preamble extraction part 6C, the reception control part 7C confirms the ID information of the RFID tag 1 that has transmitted the tag response signal based on the data part (S81). Then, the reception control unit 7C associates and registers the distance information received from the position measurement unit 8 and the ID information of the RFID tag 1 (S82). Note that the information obtained by combining the ID information of the RFID tag 1 and the distance is registered in a recording unit (not shown) provided in the communication control unit 7, and then transmitted to the external device via the external communication unit 9 shown in FIG. The Thus, the distance measurement process is completed.

(Position estimation process)
In the above description, the distance between the RFID tags 1 is measured. However, the direction of the position of each RFID tag 1 when viewed from the reader / writer 2 may also be measured. By doing this, the distance and direction of each RF ID tag 1 can be specified, and therefore the location of each RFID tag 1 can be specified. As a method for estimating the position of the RFID tag 1, there is a method in which a plurality of antenna elements of the receiving antenna 4 are arranged in an array and a difference in phase of a signal received by each antenna element is detected. Below, the estimation process of the presence position direction of this RFID tag 1 is demonstrated.

  FIG. 16 is a diagram schematically illustrating an estimation process of the existence position direction of the RFID tag 1. In the figure, the receiving antenna 4 is composed of two antenna elements, a first antenna element 4A and a second antenna element 4B. Further, θ is an angle indicating the direction in which the RFID tag 1 is present. This θ is an angle when the normal direction of the plane including both radio wave reception points in the first antenna element 4A and the second antenna element 4B is 0 °.

When the interval between the radio wave reception points in the first antenna element 4A and the second antenna element 4B is d, the phase difference Δφ of the signals received by the first antenna element 4A and the second antenna element 4B is expressed by the following equation: It is represented by

よって、位相差△φに基づいて、存在位置方向θは次の式で表される。

すなわち、位相差△φを求めることによって、存在位置方向θを求めることができる。 Here, if d = λ / 2, the phase difference Δφ is expressed by the following equation.

Therefore, the existence position direction θ is expressed by the following expression based on the phase difference Δφ.

That is, the existence position direction θ can be obtained by obtaining the phase difference Δφ.

  FIG. 17 shows the configuration of the reader / writer 2 when the direction is calculated. 4 differs from the configuration shown in FIG. 4 in that the position measurement unit 8 is provided with a direction calculation unit 8C and the reception processing unit 5 is provided with a selector 6D. Yes. The other configuration is the same as the configuration shown in FIG.

  The selector 6D selectively switches between a signal received by the first antenna element 4A and a signal received by the second antenna element 4B in the receiving antenna 4 and transmits the signals to the amplifying unit 6A1 and the amplifying unit 6A2. The selection control of the selector 6D is performed by the reception control unit 7C.

  The direction calculation unit 8C acquires information on the phase difference between the signal received by the first antenna element 4A and the signal received by the second antenna element 4B from the phase information acquisition unit 8A, and based on the information, the direction calculation unit 8C Thus, the existence position direction θ of the RFID tag 1 is calculated. Then, the reception control unit 7C acquires the distance information calculated by the distance calculation unit 8B and the existing position / direction information calculated by the direction calculation unit 8C, and transmits this information to the area determination unit 10 shown in FIG. To do.

  The area determination unit 10 determines whether or not the RFID tag 1 is located within a predetermined question area (communication area) based on the distance information and the existing position / direction information as position information. At this time, the area determination unit 10 determines whether the RFID tag 1 is present in the communication area based on the area information stored in the area information storage unit 11.

  Note that the method for obtaining the existence position direction θ of the RFID tag 1 is not limited to the above method, and various known methods can be used. For example, techniques for estimating a direction of arrival (DOA) include a beamformer method, a capon method, an LP (linear prediction) method, a min-norm method, a MUSIC method, and an ESPRIT method.

(Flow of position estimation processing)
Next, the flow of the position estimation process in the reader / writer 2 will be described with reference to the flowcharts shown in FIGS.

First, the control when the position estimation process is started, in S91, the frequency controller 7A is a PLL section 5A so that frequency of the carrier signal as a first frequency f ₁ at the time of transmitting the R / W request signal To do.

Next, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. The transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S92). When the R / W request signal is transmitted, CW (continuous carrier wave) is subsequently transmitted at the first frequency f ₁ (S93).

After that, when the RFID tag 1 detects the R / W request signal, it subsequently returns a tag response signal having a carrier frequency corresponding to the first frequency f ₁ of the detected CW (continuous carrier wave). The reception antenna 4 receives this tag response signal. At this time, the selector 6D has selected the first antenna element 4A, the reception processing unit 6 performs reception processing based on the signal received by the first antenna element 4A (S94), and phase information acquisition The unit 8A performs a phase information acquisition process (S95).

That is, in the reception processing unit 6, the frequency conversion unit 6B multiplies the reception signal input from the amplification unit 6A and the carrier signal output from the PLL unit 5A based on the above mathematical expressions 4 to 6. Thus, the I signal and the Q signal are obtained. When the phase information acquisition unit 8A receives the I signal and the Q signal from the frequency conversion unit 6B, the phase information acquisition unit 8A calculates the phase change amounts φ ₁ and φ ₂ of the first frequency f ₁ based on the mathematical expressions 7 to 8 described above. The calculated frequency is stored in the table in correspondence with the frequency (first frequency f ₁ ) used as the carrier signal (S95).

  When the reception processing unit 6 finishes receiving the tag response signal from the RFID tag 1 (S96), the phase information acquisition unit 8A ends the phase information acquisition process (S97). Thereafter, the transmission processing unit 5 ends the transmission of CW (continuous carrier wave), that is, the transmission of a signal consisting of one frame (S98). The reception control unit 7C determines whether or not reception signals of all frequencies to be received have been received. If it is determined that all reception signals have not been received (NO in S99), the process returns to S91. On the other hand, when it is determined that reception signals of all frequencies to be received have been received (YES in S99), distance calculation is performed in distance calculation unit 8B (S100), and the process proceeds to S101. Note that the position measurement unit 8 may calculate the distance not only by calculating the distance based on the phase information, but also by a method applying the MUSIC method as described above. The distance calculation may be performed before and after S111 and S112, which will be described later.

In S101, the selector 6D is switched to select the second antenna element 4B. Then, R / W request signal and CW (continuous carrier wave) is transmitted by the first frequency _{f 1} based on the control of the transmission controller 7B (S102 from S104). When the RFID tag 1 detects the R / W request signal, it subsequently returns a tag response signal having a carrier frequency corresponding to the first frequency f ₁ of the detected CW (continuous carrier wave). The reception antenna 4 receives this tag response signal. At this time, the selector 6D has selected the second antenna element 4B, and the reception processing unit 6 performs reception processing based on the signal received by the second antenna element 4B (S105).

  That is, in the reception processing unit 6, the frequency conversion unit 6B multiplies the reception signal input from the amplification unit 6A and the carrier signal output from the PLL unit 5A based on the above mathematical expressions 4 to 6. Thus, the I signal and the Q signal are obtained and output to the phase information acquisition unit 8A. When reception of the tag response signal from the RFID tag 1 is completed in the reception processing unit 6 (S106), the transmission processing unit 5 ends transmission of CW (continuous carrier wave), that is, transmission of a signal consisting of one frame (S107). .

  Next, the processing from S108 to S109 is performed regarding the direction calculation processing.

  In S108, the phase information acquisition unit 8A detects the phase difference between the signal received by the first antenna element 4A and the signal received by the second antenna element 4B, and based on this, the direction calculation unit 8C The existence position direction (existence direction) of the tag 1 is calculated (S109). Note that when direction estimation is performed based on the phase difference between the antenna elements as described above, it is necessary to compare the phase difference at a certain (same) frequency.

Thereafter, the reception control unit 7C acquires the distance information calculated by the distance calculation unit 8B and the existing position / direction information calculated by the direction calculation unit 8C, and transmits this information to the area determination unit 10. The area determination unit 10 calculates the position of the RFID tag 1 based on the distance information and the existing position / direction information (S110). Thus, the position measurement process is completed.
(Simultaneous transmission of multiple frequencies within one frame)

  In the above, the reader / writer 2 changes the carrier frequency one or more times during the transmission of the R / W request signal and CW (continuous carrier wave) consisting of one frame, so that the carrier frequency changes one or more times during the transmission. A tag response signal composed of a frame is received, and a distance measurement is performed based on the received tag response signal. On the other hand, the carrier frequency for transmitting the R / W request signal consisting of one frame and CW (continuous carrier wave) is composed of a plurality of frequency components, thereby comprising one frame of a carrier frequency having a plurality of frequency components. The tag response signal can be received and the distance can be measured based on the tag response signal.

As shown in FIG. 20 (a), the reader / writer 2 always transmits a specific signal, while returning a tag response signal when requesting the RFID tag 1 to transmit a tag response signal. The requested R / W request signal is transmitted. Here, the frequency control unit 7A includes a PLL unit 5A so that the carrier frequency of the R / W request signal (more specifically, the CW (continuous carrier wave) following the R / W request signal) is composed of a plurality of frequency components. To control. In the example shown in FIG. 20A, the control is performed so that the carrier frequency is composed of the first frequency f ₁ , the second frequency f ₂ , and the third frequency f ₃ .

The RFID tag 1 constantly monitors the signal sent from the reader / writer 2 and, when detecting that the R / W request signal has been received, transmits the tag response signal in response to the signal. Here, the tag response signal is transmitted at a carrier frequency corresponding to a carrier frequency composed of a plurality of frequency components in the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal). In the example shown in FIG. 20B, the tag response signal has a frequency f ₁ in the first period, a frequency f ₂ in the _second period, and a frequency f ₃ in the third period.

  By receiving such a tag response signal, the position measuring unit 8 can detect the state of the received signal at a plurality of different frequencies.

  A configuration for realizing this will be described below with reference to FIG.

  In the configuration shown in FIG. 4, in the configuration shown in FIG. 4, the transmission processing unit 5 is provided with transmitters 5D1, 5D2, and 5D3 and a synthesizer 5E corresponding to each frequency, and the reception processing unit 6 has a bandwidth. The difference is that pass filters 6C1, 6C2, 6C3 and mixers 6B3, 6B4, 6B5 as frequency converters 6B are provided. The other configuration is the same as the configuration shown in FIG.

  In the communication control unit 7, the frequency control unit 7A is configured so that the carrier frequency of the R / W request signal (more specifically, the CW (continuous carrier wave) following the R / W request signal) is composed of a plurality of frequency components. The PLL unit 5A is controlled. The carrier signals generated by the PLL unit 5A and the transmitters 5D1, 5D2, and 5D are combined by the combiner 5E, and then transmitted through the modulation unit 5B and the power amplification unit 5C.

  A reception signal received by the reception antenna 4 is branched into three paths via the amplification unit 6A and input to the bandpass filters 6C1, 6C2, and 6C3, respectively. Each of the band pass filters 6C1, 6C2, and 6C3 takes out a signal having a specific frequency component from the input reception signal and inputs the signal to the mixers 6B3, 6B4, and 6B5.

  The I signal and Q signal of each frequency component obtained by the mixers 6B3, 6B4, and 6B5 are input to the phase information acquisition unit 8A, and the amount of phase change of each frequency component and the distance calculation based thereon are performed.

  4 and 13, the reception processing unit 6 calculates the amount of change in phase of each frequency component while the transmission processing unit 5 is transmitting CW (continuous carrier wave).

  In the above example, the distance r is calculated based on the phase. However, the distance measurement process using the MUSIC method described above can be similarly applied. It is also possible to select two reception signals having higher I signal / Q signal levels and perform phase change detection and position calculation based on the two selected reception signals.

(Active type RFID tag)
In the above description, the configuration in which the RFID tag 1 is a passive type has been described. However, as described above, the RFID tag 1 may be an active type. In this case, the RFID tag 1 includes a power supply unit so that the signal generation unit that generates the tag response signal and the tag response signal generated by the signal generation unit are transmitted using a plurality of different carrier frequencies. A configuration including a frequency control unit to be controlled is conceivable. In this case, the reader / writer 2 can eliminate the need to transmit the R / W request signal.

  Similarly to the frequency control unit 7A described above, the frequency control unit in the RFID tag 1 sets a plurality of divided periods within a period in which one tag response signal is transmitted, and carrier frequencies different from each other in each divided period. It is also possible to perform control so that the carrier frequencies differ from each other every time the tag response signal is transmitted. It is also possible to control the carrier frequency so as to be composed of a plurality of frequency components.

(Application example of communication system using RFID tag)
Next, an example in which the communication system using the RFID tag according to the present embodiment is applied to a specific system will be described. FIG. 22 shows an example in which a communication system using the RFID tag is applied to a system that performs inspection and confirmation of a distributed article in a system in which the article is distributed. In the example shown in the figure, an article to which the RFID tag 1 is attached is conveyed by a plurality of belt conveyors. In addition, articles with the RFID tag 1 attached are stacked at a place away from the belt conveyor. The reader / writer 2 communicates with each RFID tag 1 in order to inspect the article conveyed by the belt conveyor. Thereby, distribution of each article can be managed.

  Note that, in such a communication system using an RFID tag, a management device that manages distribution items is provided as the external device that communicates with the reader / writer 2.

  In the case of such a system, if the communication system is an RFID tag communication system in which the communication area is not clearly set, communication is also performed with the RFID tag 1 at a position away from the belt conveyor, which does not require communication. On the other hand, according to the RFID tag communication system according to the present embodiment, the distance (or position) of the name RF ID tag 1 can be detected by the processing in the reader / writer 2, and therefore only with the RFID tag 1 to be communicated with. Communication can be performed.

  Moreover, according to the communication system using the RFID tag according to the present embodiment, the distance (or position) of each RFID tag 1 can be detected with relatively high accuracy, so that the RFID tag being conveyed to which belt conveyor line Whether it is 1 or not can be recognized on the reader / writer 2 side.

  In order to construct a communication system using an RFID tag having such a function, it is only necessary to install one reader / writer 2. That is, for example, it is possible to eliminate the necessity of providing a member for limiting the range in which radio waves reach or the need to install a plurality of reader / writers 2. Therefore, according to the communication system using the RFID tag according to the present embodiment, setting can be easily performed regardless of the installation environment.

  FIG. 23A shows an example of a case where a communication system using the RFID tag is applied to a system that monitors theft of merchandise and stocked goods in a store or the like. In this example, the communication area is set to a range in which an article to which the target RFID tag 1 is attached can originally exist, and by detecting that the article has disappeared from the communication area, the corresponding article is stolen. Determine that it may have been done. FIG. 23B shows an application example of a security system in which the RFID tag 1 is attached to a window or door and the position of the RFID tag 1 is monitored to detect that the window or door has been opened. ing. When constructing the crime prevention system as described above, it is only necessary to perform a simple setting of attaching the RFID tag 1 conventionally used to an object. In addition, a communication system using an RFID tag can be constructed flexibly in various environments.

  In this example as well, the communication system using the RFID tag is provided with a management device that performs crime prevention management as the external device that communicates with the reader / writer 2.

  FIG. 24 shows an example in which this RFID tag communication system is applied to a place where a ticket gate such as a station or a movie theater is required. In recent years, for example, a ticket gate using an RFID tag is widely used in a ticket gate of a station. In this system, a ticket gate is provided by providing a reader / writer at a gate. On the other hand, according to the RFID tag communication system according to the present embodiment, it is possible to perform a ticket gate without providing a gate by setting the entire passage where the ticket gate is performed as a communication area. In this case, the RFID tag 1 may be built in a mobile phone possessed by the user.

  In the system application example shown in FIG. 24, if there is a user who cannot be allowed to pass due to the result of communication with the RFID tag 1, it may be necessary to identify the unauthorized user. In this case, it is possible to leave the proof of the unauthorized user and the evidence by photographing with the monitoring camera toward the position of the unauthorized user specified by the reader / writer 2.

  Also in this example, a management device that performs traffic permission management is provided in the communication system using the RFID tag as the external device that communicates with the reader / writer 2. And this management apparatus will perform imaging | photography control of the said monitoring camera.

  FIG. 25 shows an example in which a communication system using this RFID tag is applied to a keyless entry system such as an automobile. A reader / writer 2 is provided inside the automobile, and a user has a key with a built-in RFID tag 1. When the reader / writer 2 detects that the RFID tag 1 built in the key possessed by the user has entered a predetermined range around the automobile, the reader / writer 2 instructs the lock of the key to be released. As a result, the user can release the lock only by approaching the automobile while holding the key.

  Also in this example, a management device that controls and manages the lock state of the key is provided as the external device that communicates with the reader / writer 2 in the communication system using the RFID tag.

(Embodiment 2)
The communication system according to the second embodiment acquires the position information of the reflector using the configuration of performing the distance measurement process with frequency switching in one frame of the communication system described in the first embodiment. From the obtained position information, it is determined whether or not the reflector is located at a predetermined position, and different processing is performed based on the determination result.

  Hereinafter, a case where the reflector is an RFID tag will be described as an example.

  FIG. 26 is a block diagram illustrating a configuration of a communication system including the RFID tag and the reader / writer according to the second embodiment. As shown in the figure, the communication system includes one or more RFID tags l (reflectors)... And a reader / writer (information processing apparatus) 200. The RFID tag 1 and the reader / writer 200 can transmit and receive information wirelessly. Although a case where a plurality of RFID tags 1 are provided as the RFID tag 1 will be described here, the number of RFID tags may be one.

The configuration of the RFID tag 1 is the same as that of the first embodiment. Here, in particular, the RFID tag 1 constantly monitors the signal sent from the reader / writer 2 and detects that the R / W request signal has been received, and responds to it as shown in FIG. The tag response signal is transmitted. Here, the carrier frequency of the tag response signal changes according to the time change of the carrier frequency in the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal). The tag response signal has a frequency f ₁ in the first period, a frequency f ₂ in the _second period, and a frequency f ₃ in the third period. Each RFID tag may store information such as identification information (ID information) that is information for identifying each RFID tag from other RFID tags in a storage unit (not shown).

  The reader / writer 200 is a device that performs wireless communication with each RFID tag 1 and reads / writes information stored in the RFID tag 1. In the present embodiment, the reader / writer 200 reads and writes information stored in the RFID tag 1, but the present invention is not limited to this, and the information stored in the RFID tag 1 is read. It may be an RFID reader that performs only the above.

  In the present embodiment, the frequency band of radio waves transmitted and received by the reader / writer 200 is a so-called UHF band of about 800 MHz to 960 MHz. By using radio waves in such a frequency band, the reader / writer 200 can communicate with the RFID tag 1 located within a distance range of about several meters to several tens of meters. In the present embodiment, communication using the UHF band is assumed. However, the present invention is not limited to this, and the 13.56 MHz band, 2.45 GHz band, and the like as frequency bands for RFID tags are used. A frequency band may be used, and further, communication using another frequency band capable of performing wireless communication may be performed.

  The reader / writer 200 includes a transmission antenna 3, a reception antenna 4, a transmission processing unit 5, a reception processing unit 6, a communication control unit 7, a position measurement unit 208, an external communication unit 9, a position determination unit 210, an area information storage unit 211, and A processing unit 212 is provided.

  The position measurement unit 208 further includes a phase information acquisition unit 8A, a distance calculation unit 8B, and a position information acquisition unit 208C.

  The configurations of the transmission antenna 3, the reception antenna 4, the transmission processing unit 5, the reception processing unit 6, the communication control unit 7, and the external communication unit 9 are the same as those in the above-described first embodiment, and thus description thereof is omitted. Note that the reader / writer 200 may include only one reception antenna 4 or a plurality of reception antennas 4. In addition, a plurality of reception processing units 6 that perform reception processing of signals respectively received via the plurality of reception antennas 4 may be included, and signals received respectively via the plurality of reception antennas 4 may be included. The reception process may be performed by one reception processing unit 6. The antennas 3 and 4 may be provided outside the reader / writer 2. Further, the antennas 3 and 4 may be arranged at positions different from the reader / writer 2.

Here, the reader / writer 2 always transmits a specific signal, but when requesting the RFID tag 1 to transmit a tag response signal, the reader / writer 2 transmits a tag response signal as shown in FIG. It is assumed that an R / W request signal for requesting a reply is transmitted. For this reason, as described in the first embodiment, the frequency control unit 7A includes a plurality of R / W request signals (more specifically, CW (continuous carrier wave) following the R / W request signal) within a period. And the PLL unit 5A is controlled so that the carrier frequencies are different from each other in each divided period. In the example shown in FIG. 12A, three division periods are set, and the frequency f ₁ is set in the first division period, the frequency f _{2 is set} in the _second division period, and the frequency f ₃ is set in the third division period. Control is done.

  As described in the first embodiment, the timing of the frequency conversion processing of the tag response signal in the reception processing unit 6 is the R / W request signal (more specifically, CW (continuous carrier wave following the R / W request signal). )) It shall be set based on the frequency switching timing at the time of transmission.

  Further, as described in the first embodiment, in the tag response signal, the period during which the carrier frequency is switched is preferably within the period of the preamble portion. This is because, in the tag response signal, the length of the data portion varies while the length of the preamble portion is fixed, so that a period during which the carrier frequency is switched can be ensured.

  The position measurement unit 208 measures the position of the RFID tag 1 based on the received signal received from the RFID tag 1 and acquires position information that is information related to the position of the RFID tag 1. The “position information” may be any information as long as it can indicate the position of the RFID tag 1, for example, coordinate information of the RFID tag. The coordinate information may be absolute coordinate information such as latitude and longitude, or relative coordinate information based on a predetermined position, for example, the position of the information processing apparatus 200 or the receiving antenna 4. Also good. The “position information” may include information such as an angle with respect to the reference axis. “Position information” is usually three-dimensional information, but may be one-dimensional information or two-dimensional information. For example, information specifying the x-axis, y-axis, and z-axis at the position where the RFID tag 1 exists may be used, or information specifying only the x-axis and y-axis may be used. It may be information specifying only the value of. Although details will be described later, the position measurement unit 208 measures the position of the RFID tag 1 by measuring the distance between the reader / writer 2 and the RFID tag 1, measuring the direction of the RFID tag 1 when viewed from the reader / writer 2, and the like. Done with. Strictly speaking, the distance between the reader / writer 2 and the RFID tag 1 corresponds to an average of the distance between the transmission antenna 3 and the RFID tag 1 and the distance between the RFID tag 1 and the reception antenna 4 in the reader / writer 2. To do. When the RFID tag 1 is an active type, this corresponds to the distance between the receiving antenna 4 and the RFID tag 1. In this embodiment, for the sake of convenience, the distance between the reader / writer 2 and the RFID tag 1 obtained based on the tag response signal received by each receiving antenna 4, particularly the distance between the receiving antenna 4 and the RFID tag 1. Called. Here, a case will be described in which position measurement section 208 performs distance measurement processing based on tag response information whose frequency is switched within one frame, as described in the above embodiment. The position measuring unit 208 detects the states of received signals at a plurality of different frequencies by receiving a tag response signal as shown in FIG. The position measurement unit 208 can usually be realized by an MPU, a memory, or the like. The processing procedure of the position measurement unit 208 is usually realized by software, and the software is recorded in a recording medium such as a ROM. However, it may be realized by hardware (dedicated circuit).

  The configurations of the phase information acquisition unit 8A and the distance calculation unit 8B in the position measurement unit 208 are the same as those in FIG.

  The position information acquisition unit 208C in the position measurement unit 208 specifies the position where the RFID tag 1 exists based on the distance calculated by the distance calculation unit 8B. For example, when the RFID tag 1 is a passive type and a plurality of receiving antennas 4 are provided, the distance between the receiving antenna 4 and the RFID tag 1 by the distance calculation unit 8B based on the tag response signal received by each receiving antenna 4. And the sum of the distance between the transmitting antenna 3 and the RFID tag 1 is calculated for each receiving antenna 4. And if the positional information (for example, coordinate information) of each receiving antenna 4 and the transmitting antenna 3 is known, the positional information acquisition unit 208C is based on the plurality of distance information and the positional information of each receiving antenna 4. The position of the RFID tag 1 is a two-dimensional coordinate (for example, when there are three receiving antennas and three types of distances are obtained, the sum of the distances from the coordinates of each receiving antenna 4 and the coordinates of the transmitting antenna 3 is Two-dimensional coordinates obtained as intersections of three ellipses that are a set of points equal to the distance obtained by the distance calculation unit 8B) or three-dimensional coordinates (for example, four receiving antennas and four types of obtained distances) In this case, the sum of the distances from the coordinates of each receiving antenna 4 and the coordinates of the transmitting antenna 3 is an intersection of four elliptical rotators that is a set of points equal to the distance obtained by the distance calculation unit 8B. Sought It can be specified as a dimension coordinates) and the like. The coordinate information of the identified RFID tag 1 is the position information of the RFID tag 1.

  The position determination unit 210 determines whether the RFID tag 1 is present at a predetermined position based on the position information acquired by the position measurement unit 208, and acquires the determination result. The “predetermined position” may be an absolute position represented by latitude, longitude, or the like, or a relative position with respect to the position of the reader / writer 200 or the like. The “predetermined position” is, for example, “an arbitrary position in the predetermined area”, and specifically, “an arbitrary position in the predetermined space area (communication area)”. The position determination unit 210 determines whether the RFID tag 1 exists in a predetermined position by determining whether the RFID tag 1 exists in a predetermined communication area within a preset coordinate system, for example. It is determined whether or not. Area information, which is information that is set as to what spatial area the communication area is, is stored in the area information storage unit 211, for example. Here, the position determination unit 210 determines whether the position measured by the position measurement unit 208 exists in the communication area set by the area information, so that the RFID tag 1 has a predetermined position. A case will be described in which it is determined whether or not it exists. Details of this determination processing will be described later. The position determination unit 210 can usually be realized by an MPU, a memory, or the like. The processing procedure of the position determination unit 210 is usually realized by software, and the software is recorded in a recording medium such as a ROM. However, it may be realized by hardware (dedicated circuit).

  The area information storage unit 211 stores area information that is information about a predetermined area (region). The “area” described here may be any of a region in space, a region in a plane, a region on a line, or a region on a point. “Area information” is information for specifying a predetermined area. “Area information” includes, for example, one or more one-dimensional information, two-dimensional information, three-dimensional information, and the like. For example, the area information may be information that specifies all areas on the surface defined by x = 0. In addition, the area information may be information that designates an area on a line segment that has two points, (x, y) = (10, 20) and (x, y) = (60, 50). . The shape of the area specified by the area information does not matter. For example, the shape of the region specified by the area information may be a spherical region or a rectangular parallelepiped shape as long as the region is a three-dimensional space region. The area information stored in the area information storage unit 211 is set according to the environment where the reader / writer 200 is installed. The setting of the area information may be performed from an external device, for example, via the external communication unit 9, or the reader / writer 2 may be provided with a user interface for inputting area information. . The area information storage unit 211 is preferably a non-volatile recording medium, but can also be realized by a volatile recording medium.

  The processing unit 212 performs predetermined processing based on the determination result of the position determination unit 210. Specifically, “perform a predetermined process based on the determination result” means that the predetermined process is performed only when the determination result indicates that the RFID tag is present at a predetermined position. If the RFID tag indicates that the RFID tag does not exist at the position, the predetermined processing is not performed, or if the determination result indicates that the RFID tag does not exist at the predetermined position, the predetermined processing is performed. When it indicates that the RFID tag is present at the position, the predetermined processing is not performed, when the determination result indicates that the RFID tag is present at the predetermined position, and when the RFID tag is not present at the predetermined position. This is a concept including performing predetermined processes different from each other. The “predetermined process” may be any operation, for example, a process related to the RFID tag 1. Specifically, information indicating that the RFID tag 1 exists or does not exist at a predetermined position is output through the external communication unit 9 or the like, or transmitted from the RFID tag 1 For example, a process of outputting information through the external communication unit 9 or the like, a process of transmitting predetermined information to the RFID tag 1, or the like. For example, when the determination result indicates that one or more RFID tags 1 of the plurality of RFID tags 1 are arranged at a predetermined position, the processing unit 212 uses the RFID arranged at the predetermined position. Information such as identification information received by the reception processing unit 6 from the tag 1 is output to an external device (not shown) through the external communication unit 9 or the like. The output described here is a concept including display on a display, transmission to another device, output to a printer, and temporary storage in a storage medium such as a memory. The processing unit 212 may or may not include an output device such as a display. In addition, when the determination result indicates that one or more RFID tags 1 among the RFID tags 1 are disposed at a predetermined position, the processing unit 212 detects that the RFID tag 1 is disposed at the predetermined position. In response to this, predetermined information is transmitted through the transmission processing unit 5. The predetermined information is, for example, a request signal requesting the RFID tag 1 to read information in the tag, a command for instructing processing such as rewriting of information in the tag or transmission of predetermined information. In addition, the predetermined information may include identification information received by the reception processing unit 6 as information for designating an RFID tag that operates according to a command transmitted by the processing unit 212 or the like. Further, the processing performed by the processing unit 212 may be set in accordance with an instruction received from the user via a receiving unit (not shown) or the like. The processing unit 212 can usually be realized by an MPU, a memory, or the like. The processing procedure of the processing unit 212 is usually realized by software, and the software is recorded on a recording medium such as a ROM. However, it may be realized by hardware (dedicated circuit).

  Next, the operation of the communication system according to the present embodiment will be described.

  First, the operation of outputting a tag response signal consisting of one frame having a plurality of frequencies of the RFID tag 1 is the same as that in the first embodiment, and thus the description thereof is omitted.

  Next, the operation of the information processing apparatus 200 will be described using the flowchart of FIG. In the figure, the same reference numerals as those in FIG. 13 indicate the same or corresponding processing steps.

  First, when the distance measurement process is started, the frequency control unit 7A sets the frequency of the carrier signal (more specifically, the CW (continuous carrier wave) following the R / W request signal) when transmitting the R / W request signal. The PLL unit 5A is controlled so as to be switched for each of the plurality of divided periods. Then, the transmission control unit 7B controls the modulation unit 5B so as to superimpose data indicating the R / W request signal on the carrier signal. Then, the transmission signal modulated by the modulation unit 5B is amplified by the power amplification unit 5C and then output from the transmission antenna 3 (S51). When the R / W request signal is transmitted, CW (continuous carrier wave) is transmitted at a different frequency for each of the plurality of divided periods (S53, S55, S58). Thereby, the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal) whose frequency is switched for each divided period is transmitted.

When the RFID tag 1 detects the R / W request signal, followed by detecting CW carrier frequency (continuous carrier wave) (frequency _{f 1,} f 2, _{f 3)} of the carrier frequency changes according to the time variation (frequency _{f 1} , F ₂ , f ₃ ) is returned. The reception antenna 4 receives this tag response signal, the reception processing unit 6 performs reception processing (S53, S56, S59), and the phase information acquisition unit 8A performs phase information acquisition processing (S54, S57, S60). In the tag response signal received here, the carrier frequency changes according to the time change of the carrier frequency in the CW (continuous carrier wave) after the R / W request signal.

That is, in the reception processing unit 6, the frequency conversion unit 6B recognizes the preamble part in the tag response signal, and based on the above equations 4 to 6, the I signal and Q for the frequency of each divided period in the preamble part Find the signal. When the phase information acquisition unit 8A receives the I signal and the Q signal of each frequency from the frequency conversion unit 6B, the phase information acquisition unit 8A calculates the phase change amounts φ ₁ and φ ₂ of each frequency based on the above formulas 7 to 8. And stored in a table corresponding to the frequency used as the carrier signal. Here, the switching timing of each divided period is set based on the frequency switching timing at the time of transmitting the R / W request signal (more specifically, CW (continuous carrier wave) following the R / W request signal).

The frequency conversion and phase information acquisition processing for each frequency (frequency f ₁ , f ₂ , f ₃ ) in each divided period in the preamble portion of the tag response signal in the reception processing unit 6 and the phase information acquisition unit 8 A is performed in the transmission processing unit 5. This is performed while a CW (continuous carrier wave) having a corresponding frequency is being transmitted. For example, when the transmission processing unit 5 starts transmission of CW (continuous carrier wave) at the first frequency f ₁ (S52), the RFID tag 1 transmits the signal of the first division period in the preamble portion of the tag response signal to the first frequency to reply at a frequency _{f 1.} The reception processing unit 6 receives the tag response signal of the frequency f ₁ (S53), and the phase information acquisition unit 8A acquires the phase information of the frequency f ₁ (S54). After a certain period of time, the transmission processor 5 starts transmission of CW (continuous carrier wave) at the second frequency _{f 2} (S55). When receiving the CW (continuous carrier wave) of the second frequency f ₂ , the RFID tag 1 transmits a signal of the next divided period in the preamble portion of the tag response signal at the second frequency f ₂ . The reception processing unit 6 receives the tag response signal of the frequency f ₂ (S56), and the phase information acquisition unit 8A acquires the phase information of the frequency f ₂ (S57). After a certain period of time, then the transmission processing unit 5 with respect to the third frequency f _3, the reception processing section 6 and phase information acquiring section 8A repeats the same operation (S58 from S60).

  When reception of the tag response signal from the RFID tag 1 is completed in the reception processing unit 6 (S61), the transmission processing unit 5 terminates transmission of CW (continuous carrier wave), that is, transmission of a signal consisting of one frame (S62). . Thereafter, the distance calculation unit 8B calculates the distance r based on the phase information at a plurality of different frequencies stored in the table (S63).

  Here, if the number of the receiving antennas 4 is two or more, the processes of steps S53, S54, S56, S57, S59, S60, S61, S63 and the like are processed in order or in parallel for each receiving antenna. Thus, the distance r is obtained for each receiving antenna.

  The position measurement unit 208 acquires position information based on the distance r calculated in step S63 (S2701). For example, if there is only one reception antenna 4, the position measurement unit 8 acquires, as position information, information on a position where the distance of the path from the transmission antenna 3 through the RFID tag 1 to the reception antenna 4 is 2r. Further, if there are a plurality of receiving antennas 4, the position measuring unit 8 has a distance of 2r from the transmitting antenna 3 through the RFID tag 1 to each receiving antenna 4 (where r is received by each receiving antenna 4). Information on a position that satisfies the condition (distance calculated based on the tag response signal) is acquired as position information. If strict position information is not required, a circle having a radius r (where r is a distance calculated based on a tag response signal received by each receiving antenna 4) centered on each receiving antenna 4 or the like is used. Alternatively, the position information of the intersection of the spheres may be acquired as the position information of the RFID tag 1. However, it is assumed that the position information of the reception antenna 4 and the transmission antenna 3 is set in advance.

  The position determination unit 210 acquires the position information acquired in step S2701 and the area information stored in the area information storage unit 211, and determines whether or not the RFID tag 1 exists at a predetermined position ( S2702). For example, when the position information (coordinate information) acquired in step S2701 exists in the area specified by the area information, the position determination unit 210 determines that the RFID tag 1 exists at a predetermined position, and the area information is When the position information acquired in step S2705 does not exist in the designated area, it is determined that the RFID tag 1 does not exist at a predetermined position. If the RFID tag 1 is present at the predetermined position, the process proceeds to step S2703, and if not, the process proceeds to step S2704.

  The processing unit 212 performs a first predetermined process (S2703). For example, when an instruction to output the identification information of the RFID tag 1 to the outside of the reader / writer 200 is received from a user via a reception unit (not shown), the processing unit 212 determines that the RFID is present at a predetermined position. The identification information of the tag 1 is acquired based on the received tag response signal and output to the outside via the external communication unit 9 or the like. In addition, the processing unit 212 has a predetermined request signal for the RFID tag 1, for example, a request signal for writing predetermined information (for example, a write command), a request signal for setting the information to be unchangeable (for example, a lock command), When the request signal (for example, the kill command) for inactivating or disabling the RFID tag 1 is set to be transmitted, the processing unit 212 sends these request signals to the communication control unit 7. Is transmitted together with the identification information of the RFID tag 1 determined to be present at a predetermined position. Based on this instruction, the communication control unit 7 controls the transmission processing unit 5 to output the identification information of the RFID tag 1 and the request signal via the transmission antenna 3. Here, the first predetermined process may be that no process is performed. Then, the process ends.

  The processing unit 212 performs a second predetermined process (S2704). The second predetermined process is different from the first predetermined process. However, as long as the second predetermined process is different from the first predetermined process, the same process as the process described as the example of the first predetermined process described above may be used. Then, the process ends.

  In the flowchart of FIG. 27, the tag response signal received by the reception processing unit 6 in steps S53, S56, S59, etc. may be only a tag response signal transmitted from one RFID tag 1, or a plurality of tag response signals may be received. A plurality of tag response signals transmitted from the RFID tag 1 may be used. A step of determining whether or not the reception processing unit 6 has received a signal a predetermined number of times after processing (S53, S56, S59) for receiving a tag response signal when the number of RFID tags 1 is known in advance. If the signal has not been received a predetermined number of times, the processes of steps S53, S56, S59, etc. may be repeated until the predetermined number is reached. In addition, after the processing of steps S53, S56, S59, etc., there is a step of determining whether or not a predetermined time has elapsed after the transmission processing unit 5 performs the transmission processing, and when the predetermined time has not elapsed, Until the predetermined time is reached, the processes in steps S53, S56, S59, etc. may be repeated.

  In the flowchart of FIG. 27, when the RFID tag 1 is an active type tag that spontaneously transmits a signal, processing for transmitting a request signal, CW (continuous carrier wave), and the like may be omitted.

  Next, a specific operation of the communication system will be described.

  Here, it is assumed that the information processing apparatus 200 includes four or more receiving antennas 4 whose coordinates are known. Here, the distance r obtained from the tag response signal received by each receiving antenna 4 is assumed to be a distance from the coordinates of each receiving antenna 4. In addition, when a plurality of pieces of position information about one RFID tag 1 are obtained, position information that is the center between these pieces of position information is set as the position information.

  First, the process of calculating the distance r by the position measurement unit 208 based on the tag response signal received by each receiving antenna 4 is the same as that in the first embodiment, and thus the description thereof is omitted.

  Next, the position measurement unit 208 satisfies a condition that satisfies the distance r from each receiving antenna 4 (where r is a distance calculated based on the tag response signal received by each receiving antenna 4). Find the coordinates of. When a plurality of coordinates of a position satisfying such a condition are obtained, here, a coordinate serving as a center between the obtained plurality of coordinates is obtained. These coordinates are used as position information (here, coordinate information) of the RFID tag 1.

Here, for example, the area information stored in the area information storage unit 11 is information for designating a rectangular parallelepiped space region 60 as shown in FIG. 28, and this area information is the minimum in the x-axis direction. It is assumed that the value is x1, the maximum value is x2, the minimum value y1 in the y-axis direction, the maximum value is y2, the minimum value in the z-axis direction is z1, and the maximum value is z2. Assuming that the position information acquired by the position information acquisition unit 208C is (x3, y3, z3), the RFID tag 1 falls within the area specified by the area information if all of the following three conditional expressions are satisfied. Presumed to exist.

  Therefore, when the position information of the RFID tag 1 satisfies the above three conditional expressions, the position determination unit 210 determines that the RFID tag 1 exists at a predetermined position as shown in FIG. If even one conditional expression is not satisfied, it is determined that the RFID tag 1 does not exist at a predetermined position.

  Here, when the RFID tag 1 is determined not to exist at a predetermined position by the position determination unit 210, a process of performing no process is selected as the predetermined process. This process ends.

  When the position determination unit 210 determines that the RFID tag 1 is present at a predetermined position, the processing unit 212 uses the identification information acquired from the RFID tag 1 to perform a predetermined operation or user The operation etc. which received the instruction from is performed.

  For example, when an instruction to rewrite information stored in the RFID tag 1 existing at a predetermined position with predetermined information has been received from a user in advance via a reception unit (not shown), the processing unit 212 receives the request described above. Similar to the process of transmitting the signal to the RFID tag 1, request information for rewriting the information stored in the RFID tag 1 with predetermined information is transmitted. However, here, information for limiting the RFID tag 1 determined to be in a predetermined position to the transmission destination of the request information, specifically, identification information of the RFID tag 1 received by the reception processing unit 6 is included. The information is transmitted together with the request information or included in the request information.

  Each RFID tag 1 that has received the request information determines whether or not the identification information stored in the storage unit (not shown) matches the identification information transmitted together with the request information. The process indicated by the received request information is executed. In this case, the RFID tag 1 with the matching identification information executes a process instructed by the request information, and rewrites part or all of the information stored in the storage unit to predetermined information.

  In addition, when it is set in advance that the identification information of the RFID tag 1 existing at a predetermined position is transmitted to another device (not shown), the processing unit 212 receives the RFID tag 1 received by the reception processing unit 6. The identification information is transmitted to other devices by wired or wireless communication.

  In the above specific example, as shown in FIG. 28, the case where the area specified by the area information has a rectangular parallelepiped shape has been described. However, in the present invention, the shape of the area does not matter as described above. For example, the area specified by the area information may be spherical or one point in the space. The area specified by the area information may be a straight line or a line segment in the space.

  Hereinafter, an example of processing of the position determination unit 210 when the area specified by the area information has a spherical shape will be described with reference to FIG.

For example, as shown in FIG. 29, the area information stored in the area information storage unit 211 is information specifying a spherical space area 61, and this area information is the coordinate A ( x1, y1, z1) and information specifying the radius r of the sphere. The position information acquired by the position information acquisition unit 208C is assumed to be coordinates B (x2, y2, z2). In this case, if the distance L between the coordinate A of the center point and the coordinate B as the position information is obtained and L ≦ r holds, it is considered that the RFID tag 1 exists in the area indicated by the area information. The distance L is obtained by the following formula.

  Therefore, the position determination unit 210 calculates the distance L using this equation. If L ≦ r, the position determination unit 210 determines that the RFID tag 1 exists at a predetermined position, and if L> r, the RFID tag 1 It determines with not existing in a predetermined position.

  In the present embodiment, the area information may be information specifying a two-dimensional area or a one-dimensional area. For example, when the area information is information specifying a two-dimensional area, for example, information specifying only the x-axis range and y-axis range of the area, the two-dimensional position information of the RFID tag 1 It is determined whether or not the RFID tag 1 exists at a predetermined position by determining whether or not the information of x, for example, the value of the x coordinate and the value of the y coordinate are included in the range specified by the area information can do.

  Similarly, when the area information is information specifying a one-dimensional region, for example, information specifying only the range of the x-axis value of the region, one-dimensional information of the position information of the RFID tag 1, for example, By determining whether or not the value of the x coordinate is included within the range specified by the area information, it is possible to determine whether or not the RFID tag 1 is present at a predetermined position.

  FIG. 30 is a diagram illustrating an example of a package sorting system 70 using the information processing apparatus 200. In this parcel sorting system 70, the information processing apparatus 200 reads information on the RFID tags 1 attached to a plurality of parcels 72 to 74 flowing on the belt conveyor 71, acquires information on the delivery destination of each parcel, and sorts parcels. Based on the acquired information, the sorting device 77, which is a device for performing the processing, places the packages 72 to 74 on the belt conveyor 71 on the belt conveyors 71a and 71b corresponding to the respective delivery destinations. ˜74 can be sorted by delivery destination. The sorting device 77 has, for example, a mechanism for moving the cargo arranged on the upper part thereof to the belt conveyor 71a or the belt conveyor 71b.

  Here, the area information stored in the area information storage unit 211 sets an area 79 located above the sorting device 77. The information processing apparatus 200 acquires the position information of the RFID tag 1, and when it is determined that the RFID tag 1 is located in the area 79, the identification information of the RFID tag is separated by wired or wireless communication. 77. The sorting device 77 has a database (not shown) that stores information in which identification information in the RFID tag 1 is associated with information on the destination of each package. When the information is received from the information processing apparatus 200, information on the delivery destination of the package to which the RFID tag 1 is attached is acquired from the database based on the identification information, and on the sorting device 77 according to the information on the delivery destination. , In this case, the luggage 73 in the region 79 is placed on either the belt conveyor 71a or the belt conveyor 71b. Note that the configuration of the belt conveyors 71, 71a, 71b and the like and the configuration in which the sorting device 77 places the packages on the predetermined belt conveyors 71a, 71b are well-known techniques, and thus the description thereof is omitted.

  In the package sorting system 70, the information processing apparatus 200 determines that only the RFID tag 1 attached to the package 73 in the region 79 on the sorting apparatus 77 is the RFID tag 1 existing at a predetermined position. Only the identification information of the RFID tag 1 is transmitted to the sorting device 77. Also, RFID tags that do not need to be read at the present time, such as the RFID tag 1 attached to the luggage 74 moving on the belt conveyor 71 and the RFID tag 1 attached to the luggage 72 on the belt conveyor 71a. That is, for the RFID tag that is not in the region 79, the information in the tag can be prevented from being read. For this reason, since the identification information transmitted from the information processing device 200 is the identification information of the RFID tag 1 attached to the package on the sorting device 77, the sorting device 77 uses the sorting information 77 based on this identification information. The delivery destination for the above package can be determined, and the package can be sorted according to the delivery destination.

  When a conventional RFID tag reading device, such as a so-called tag reader, is used in such a system, a tag reader having a short communication distance is arranged above the sorting device 77, and the package has moved to the information of the sorting device 77. For example, it is necessary to limit the communicable area by making it possible to read out only the RFID tag with a tag reader or providing a radio wave blocking structure or the like. However, when a tag reader with a short communication distance is used, it is necessary to always provide the tag reader in the vicinity of the sorting device 77. However, depending on the location, it is difficult to arrange the tag reader, and there is a problem that the tag reader cannot be arranged. Furthermore, when the site operation is changed and the position of the sorting device 77 is changed, or when the position for reading the RFID tag of the package is changed, the position where the tag reader is provided needs to be changed in accordance with the change. The work is not easy. Even when a radio wave blocking structure or the like is used, it is necessary to change the arrangement or setting of the radio wave blocking structure or the like in accordance with the change of the arrangement of the sorting device 77, and the case where a tag reader with a short communication distance is used. Similar problems arise.

  On the other hand, if the information processing apparatus 200 according to the present embodiment is used, the area information may be set in the area of the space on the sorting apparatus 77, and therefore the information processing apparatus 200 itself can be arranged freely. The problem that the processing device 200 is not disposed does not occur. In addition, when changing the position of the sorting device 77, the reading position of the RFID tag, etc., it is only necessary to change the area specified by the area information, so that handling is very easy. Convenience in system operation is also high.

  As described above, according to the present embodiment, the position information of the RFID tag 1 is acquired, and it is determined whether the RFID tag 1 is present at a predetermined position based on the position information. Different predetermined operations can be performed depending on the existing position. For example, the information processing apparatus may selectively acquire information such as identification information of an RFID tag that exists at a predetermined position, for example, an area, and may not acquire information about an RFID tag that exists at another position. It becomes possible.

  Also, the distance between the receiving antenna 4 and the RFID tag 1 is calculated using a tag response signal in which a plurality of divided periods are set in one frame and each divided period is transmitted by a different carrier frequency. Since the position information is acquired, the position measuring unit 208 can calculate the distance by analyzing the signal state in each divided period in one tag response signal. As a result, there is no need to calculate the distance based on tag response signals of a plurality of frames having different carrier frequencies, and even when the RFID tag 1 is moving, a tag response signal of a plurality of frames is received. An error in position detection due to movement of the RFID tag 1 in the transmission interval between the tag response signal and the tag response signal can be reduced. As a result, the accuracy of the position information of the RFID tag 1 acquired by the position measuring unit 208 can be improved. In addition, the distance can be calculated only by transmitting / receiving one request signal and one reflected signal, thereby reducing the transmission / reception of signals required for calculating the distance. The distance can be calculated without reducing the communication efficiency.

  In addition, since it is determined whether or not the RFID tag 1 exists in a predetermined position by determining whether or not the position information of the RFID tag 1 exists in the area specified by the area information. By simply changing the area information, the area used for determining the position where the RFID tag exists can be easily changed without moving the information processing apparatus.

  In the present embodiment, the RFID tag using the configuration in which the distance r between the information processing apparatus 200 and the RFID tag 1 is calculated using tag response information having different frequencies in one frame in the first embodiment. In the present invention, the other distance measurement processing described in the first embodiment is performed (for example, FIG. 1, FIG. 4, FIG. 14, FIG. 17, FIG. 21). The position information of the RFID tag 1 may be acquired by using the above-described structure etc., and the position information of the RFID tag 1 may be combined by any combination of the structures described in the first embodiment. May be obtained. For example, the distance measurement process using the MUSIC method described in the first embodiment can be similarly applied. It is also possible to select two reception signals having higher I signal / Q signal levels and perform phase change detection and position calculation based on the two selected reception signals.

  In the above example, the position information of the RFID tag 1 is specified based on the position information of one or more receiving antennas 4 and the like and the distance information calculated from the tag response information received by the receiving antenna 4. The present invention is not limited to such a configuration. For example, the position measurement unit 208 of the present embodiment is configured such that the position calculation unit 8 having the direction calculation unit 8C as described with reference to FIG. By detecting the direction of the RFID tag 1 when viewed, the position information of the RFID tag 1 may be specified by appropriately combining information on this direction, distance information, position information of the receiving antenna 4 and the like. .

  In the present embodiment, the device that detects whether or not the RFID tag 1 is present at a predetermined position, the information stored in the RFID tag 1 is read, the information is written to the RFID tag, The device that outputs the request information may be a different device. The same applies to other embodiments.

  In the above embodiment, each component may be configured by dedicated hardware, or a component that can be realized by software may be realized by executing a program. For example, each component can be realized by a program execution unit such as a CPU reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory. The same applies to other embodiments. Note that the software that realizes the information processing apparatus in the above embodiment is the following program. That is, the program includes a transmission step of transmitting a request signal, which is a signal consisting of one frame, using radio waves having different carrier frequencies to a computer, and the request signal transmitted in the transmission step is reflected by a reflector. And receiving a reflected signal, which is a signal composed of one frame generated by being reflected while receiving a predetermined modulation by the antenna, between the reflected signal received in the receiving step and the request signal. Phase information acquisition step for calculating the phase change amount for each carrier frequency transmitted by the transmission means, and the phase change amount and carrier frequency for each carrier frequency acquired by the phase information acquisition step, Calculated by a distance calculating step for calculating a distance between the antenna and the reflector, and the distance calculating step The position information acquisition step of acquiring position information that is information related to the position of the reflector based on the separation, and the position of the reflector is present based on the position information acquired in the position information acquisition step. It is a program for executing a position determination step for determining whether or not, and outputting a determination result, and a processing step for performing a predetermined process based on the determination result.

  In the above program, in a transmission step for transmitting information, a reception step for receiving information, etc., processing performed by hardware, for example, processing performed by a modem or an interface card in the transmission step (only performed by hardware). Not included) is not included. The same applies to other embodiments.

  Further, this program may be executed by being downloaded from a server or the like, and a program recorded on a predetermined recording medium (for example, an optical disk such as a CD-ROM, a magnetic disk, a semiconductor memory, or the like) is read out. May be executed by

  Further, the computer that executes this program may be singular or plural. That is, centralized processing may be performed, or distributed processing may be performed. The same applies to other embodiments.

(Embodiment 3)
The information processing apparatus according to the present embodiment determines whether or not the reflector is present in a predetermined region and determines whether or not the reflector is present at a predetermined position in the information processing apparatus described above. Instead of determining, whether or not the reflector exists at a predetermined position is determined based on whether or not the relative positional relationship between the position of the reflector and the position of the information processing device satisfies the predetermined relationship. It is what I did.

  Hereinafter, a case where the reflector is an RFID tag will be described as an example.

  FIG. 31 is a block diagram showing a configuration of a communication system including a reader / writer (information processing apparatus) 202 according to the present embodiment. The configuration of the RFID tag 1 is the same as that shown in FIG.

  The reader / writer 202 includes a transmission antenna 3, a reception antenna 4, a transmission processing unit 5, a reception processing unit 6, a communication control unit 7, a position measurement unit 208, an external communication unit 9, a processing unit 212, a local position information acquisition unit 410, and A position determination unit 411 is provided. The configurations of the transmission antenna 3, the reception antenna 4, the transmission processing unit 5, the reception processing unit 6, the communication control unit 7, the position measurement unit 208, the external communication unit 9, and the processing unit 212 are the same as in FIG. Is omitted.

  The own position information acquisition unit 410 acquires own position information that is information related to the position of the own device. The own device described here is specifically the reader / writer 202. The self position information is the same as the position information of the RFID tag except that it is information related to the position of the reader / writer 202 instead of the RFID tag. When the receiving antenna 4 is disposed away from the reader / writer 202 main body, one position of the receiving antenna 4 may be used as the own position information. The own position information acquisition unit 410 may use information regarding the position of any part of the reader / writer 202 as own position information. The self-location information may be information related to the position where the processing for acquiring the position information is performed. In addition, the own position information acquisition unit 410 may acquire the own position information in any way. For example, the preset coordinate information of the reader / writer 202 may be stored as self-location information in a storage medium such as a memory (not shown). Moreover, you may receive and acquire the own position information transmitted from another apparatus etc. as needed via the receiving part etc. which are not shown in figure. Further, when the position information is absolute coordinates such as latitude and longitude, the reader / writer 202 and the receiving antenna 4 are provided with a GPS (global positioning system) receiver (not shown) as a means for acquiring the absolute coordinates. The absolute coordinate information acquired by the GPS receiver may be used as the own position information of the reader / writer 202 and the receiving antenna 4. Further, the principle of a system for measuring a position such as PHS may be used. Further, the RFID tag similar to the RFID tag 1 is provided in the reader / writer 202, and the positional information of the RFID tag is acquired by the same processing as that of the position measuring unit 208. The acquired positional information is the reader / writer 202. It is good also as position information. Note that the information on the position of the receiving antenna 4 that is not at the same position as the main body of the reader / writer 202 is necessary when acquiring the position information of the RFID tag 1, so that it may be set in advance or acquired by some means. It is necessary to keep. For example, regarding the position information of the receiving antenna 4, one or more positioning RFID tags whose position information is known are provided in advance, and the position of the RFID tag is detected by using the receiving antenna 4. The position may be obtained. Further, a GPS receiver or the like may be provided on the reception antenna 4 and information on the position of the reception antenna 4 may be acquired using this GPS receiver. The self-location information acquisition unit 410 can be usually realized by an MPU, a memory, or the like. The processing procedure of the own position information acquisition unit 410 is usually realized by software, and the software is recorded on a recording medium such as a ROM. However, it may be realized by hardware (dedicated circuit).

  The position determination unit 411 determines whether the RFID tag 1 is present at a predetermined position based on the position information acquired by the position measurement unit 208. Specifically, by determining whether or not the position information of the RFID tag 1 and the own position information of the reader / writer 202 (or the receiving antenna 4) satisfy a predetermined relationship, the RFID tag 1 It is determined whether or not it exists at the position. The “predetermined relationship” described here may be any relationship as long as the positional relationship between the position of the reader / writer 202 (or the receiving antenna 4) and the position of the RFID tag 1 can be specified. For example, the position determination unit 411 may determine that the predetermined relationship is satisfied if the distance between the position of the reader / writer 202 and the position of the RFID tag 1 is within a predetermined range. If the direction in which the RFID tag 1 is located with respect to the reader / writer 202 is a predetermined direction, it may be determined that a predetermined relationship is satisfied. Alternatively, it may be determined that the predetermined relationship is satisfied if the difference between the values of the x, y, and z coordinates of the reader / writer 202 and the RFID tag 1 are all within a predetermined range. The determination as to whether or not the position information of the RFID tag 1 and the own position information of the information processing apparatus 202 satisfy a predetermined relationship is information for setting a determination condition stored in a memory or the like (not shown), for example. This is performed based on the determination information. The position determination unit 411 may have this determination information. The position determination unit 411 can usually be realized by an MPU, a memory, or the like. The processing procedure of the position determination unit 411 is usually realized by software, and the software is recorded on a recording medium such as a ROM. However, it may be realized by hardware (dedicated circuit).

  Next, the operation of the reader / writer 202 will be described using the flowchart of FIG. 32, the same reference numerals as those in FIG. 27 indicate the same or corresponding processing steps, and the description thereof will be omitted.

  (Step S3201) The own position information acquisition unit 410 acquires own position information. The own position information acquisition unit 410 may acquire the own position information stored in advance in a memory or the like, for example. In addition, an RFID tag is provided in the reader / writer 202 in advance, and based on tag response information transmitted from the RFID tag, position information of the RFID tag is obtained by the same processing as the processing in steps S51 to S63 and step S2701. And the position information may be used as the own position information. Note that the processing in step S3201 may be executed as processing prior to step S51.

  (Step S3202) The position determination unit 411 determines whether or not the own position information acquired in step S3201 and the position information of the RFID tag 1 acquired in step S2701 satisfy a predetermined relationship. If the predetermined relationship is satisfied, the process proceeds to step S2703. If the predetermined relationship is not satisfied, the process returns to step S2704.

  Note that the processing is ended by powering off or interruption for aborting the processing in the flowchart in FIG.

  Next, a specific example will be described. FIG. 33 is a schematic diagram showing an example in which the reader / writer 202 of the present embodiment is used as an automatic ticket gate system at a station. As shown in FIG. 43, the reader / writer 202 is installed at the ticket gate of the station. Here, the own position information of the reader / writer 202 is set to (x1, y1, z1) in advance, and the determination information used by the position determination unit 411 as a determination condition is from the reader / writer 202 to the ticket gate. It is assumed that a distance value R to the farthest position is set.

  First, it is assumed that the reader / writer 202 periodically transmits a command (R / W request signal) for reading information of the RFID tag 1.

  Now, when a user 2001a having a commuter pass with a built-in RFID tag 1 tries to enter the station from the ticket gate (entrance direction), the RFID tag 1 in the user's commuter pass is stored in the RFID tag 1. Identification information and the like are transmitted as a response signal (reflected signal). When the reader / writer 202 receives a signal from the RFID tag 1 via the receiving antenna 4, the position measurement unit 208 acquires coordinate information that is position information of the RFID tag 1. It is assumed that this coordinate information is (x2, y2, z2). In addition, the own position information acquisition unit 410 acquires coordinate information (x1, y1, z1) that is own position information stored in a memory or the like.

Next, the position determination unit 411 determines whether or not the own position information and the position information of the RFID tag 1 satisfy a predetermined condition set by the determination information. Specifically, it is determined whether the distance between the position indicated by the own position information and the position indicated by the position information of the RFID tag 1 is R or less. That is, it is determined whether or not the following expression is satisfied.

  If the above formula is satisfied, it is determined that the RFID tag 1 is present in the ticket gate area (or in the ticket gate passage), and the reader / writer 202 reads the information in the RFID tag 1, and can the user 2001a pass the ticket gate? Determine whether or not. That is, if there is an RFID tag 1 in the area 2000 including the ticket gate, information on the RFID tag 1 is read out.

  In addition, when the user 2001b having the RFID tag 1 is away from the ticket gate, the reader / writer 202 similarly acquires the position information of the RFID tag 1, but this position information does not satisfy the above-described formula, It is determined that the predetermined relationship with the self-location information is not satisfied, and the information of the RFID tag 1 is not read out. That is, the reader / writer 202 does not read information about the RFID tag 1 in the commuter pass of the user 2001b away from the ticket gate.

  As described above, according to the present embodiment, the position information of the RFID tag 1 and the own position information of the reader / writer 202 are acquired, and whether or not the position information and the own position information satisfy a predetermined relationship is determined. The determination result is output and the determination result is output, and the determination result is used to determine whether or not to perform a predetermined operation on the RFID tag 1. As a result, the operation of the reader / writer 202 can be determined based on the relative positional relationship between the RFID tag 1 and the reader / writer 202. For example, the information processing apparatus can selectively acquire information such as identification information of RFID tags having a predetermined relative positional relationship.

  In addition, a relative area where the RFID tag 1 is disposed with respect to the position of the reader / writer 202 for causing the reader / writer 202 to perform a predetermined operation only by changing conditions for determining whether or not the predetermined relationship is satisfied. Can be easily changed without moving the information processing apparatus.

  In the automatic ticket gate system as described above, the information processing apparatus 200 described in the second embodiment may be applied. In this case, the area 2000 may be set by area information.

  When applied to an entrance / exit (getting off) combined type automatic ticket gate (automatic ticket gate) system, the reader / writer 202 uses the processing unit 212 or the like to detect the position information of the RFID tag 1 and the own position information of the reader / writer 202. From which time the RFID tag 1 is approaching the ticket gate (ticket gate passage) from the time-dependent change in the positional relationship, the passenger who owns the RFID tag 1 checks the ticket gate from which direction. Depending on whether you approach the entrance (the ticket gate passage) (or enter the area 2000 including the ticket gate), the processing direction of the automatic ticket gate system (specifically, the passage permission direction) is set to the entrance direction or the exit direction. You may make it switch dynamically. Furthermore, when a plurality of automatic ticket gate systems are installed (for example, five), the reader / writer 202 uses the processing unit 212 or the like to approach the number of passengers (number of RFID tags approaching) according to the direction to the ticket gate or Calculate the ratio of the number of passengers, and the number of approaching passengers by the calculated direction (number of approaching RFID tags) or the ratio of the processing direction (passing permission direction) of multiple automatic ticket gate systems according to the number ratio, For example, it may be switched dynamically to 2 to 3 or 3 to 2. For example, as a result of the judgment of the reader / writer 202, when the ratio of the customer who intends to enter the station premises and the customer who intends to exit the station is 1 to 4 with respect to the ticket gate (ticket gate passage) Of the five automatic ticket gate systems, the passage permission direction is controlled so that only one can pass only in the direction entering the station, and the remaining four are allowed only in the direction leaving the station. To control. Control of the passage permission direction of the automatic ticket gate system is performed, for example, by lowering a gate for disallowing passage from a direction that does not permit passage, or by displaying that the passage is impossible.

  Conventionally, even if a plurality of automatic ticket gate systems are provided, the processing direction (passing permission direction) of the automatic ticket gate system has not been dynamically controlled based on the detailed number of people going to the automatic ticket gate system. For this reason, even if the composition ratio of customers entering and exiting the station through the ticket gate changes, the automatic ticket gate system in which the passage permission direction enters the station, and the passage permission direction exits from the station The composition ratio with the automatic ticket gate system which is the direction was not dynamically controlled. As a result, there are cases where the composition ratio of customers by passing direction and the composition ratio of the automatic ticket gate system by passing permission direction are greatly different, and the ticket gate is often congested. However, with the configuration as described above, the pass permission direction of a plurality of automatic ticket gate systems is dynamically controlled based on the direction of the customers heading to the automatic ticket gate system and the number of passengers, so And the composition ratio of the automatic ticket gate system according to the passage permission direction can be made substantially the same ratio, and congestion of the ticket gate can be eliminated.

  In addition, in a conventional system that performs ticket check by contactless card touch determination using a ticket with a built-in RFID tag, an automatic ticket checker (automatic ticket check passage) with a card touch by a passenger and a passenger getting off at the same time When entering the station, it may not be possible to determine which customer should be given priority, and customers may get stuck in the ticket gate, but if this is applied, congestion at the ticket gate can be eliminated. .

  Note that the information processing apparatus 200 described in the second embodiment may be used instead of the reader / writer 202 as the information processing apparatus used in the automatic ticket gate system as described above. In this case, for example, a plurality of areas are set in the vicinity of the ticket gates, and the operation unit 206 or the like of the information processing apparatus 200 determines which area the RFID tag 1 has moved from to which area over time. It may be determined from which direction is approaching the ticket gate.

  Here, processing for obtaining the position of one receiving antenna 4 using a positioning RFID tag, which is an RFID tag in which position information is set in advance, will be described. Here, as an example, the coordinates of the reception antenna 4 are obtained from the position information of the passive RFID tag for positioning and the distance from the RFID tag acquired from the signal transmitted from the RFID tag to the reception antenna 4. The process to acquire is demonstrated.

  FIG. 34A and FIG. 34B are schematic diagrams for explaining the process of detecting the position of the receiving antenna 4. Here, a case will be described in which two active RFID tags 1a and RFID1b in which position information is preset are used as position detection RFID tags. The position information of the RFID tag 1a is coordinates A (xa, ya, za), and the position information of the RFID 1b is coordinates B (xb, yb, zb). Note that the configuration of the reader / writer 202 other than the receiving antenna 4 is omitted here. Here, it is assumed that the reception antenna 4 and the transmission antenna are also used.

  First, as shown in FIG. 44 (a), distances between the receiving antenna 4, the RFID tag 1a, and the RFID tag 1b are obtained by the same processing as in the second embodiment. That is, a request signal is transmitted from the transmitting antenna (in this case, the receiving antenna 4 is used), and in response to this, a one-frame tag response signal transmitted from the RFID tag 1a and a one-frame tag transmitted from the RFID tag 1b. The response signal is received by one receiving antenna 4. Then, based on these tag response signals, the distance Ra between the receiving antenna 4 and the RFID tag 1a is obtained by the same processing as that described in the second embodiment. Similarly, the distance Rb between the receiving antenna 4 and the RFID tag 1b is obtained.

  Next, based on the coordinates A (xa, ya, za) of the RFID tag 1a and the coordinates B (xb, yb, zb) of the RFID tag 1b, the distance from the RFID tag 1a is a distance Ra, and the RFID tag 1b The coordinate C of the position where the distance from is the distance Rb is obtained. The coordinates C (xc, yc, zc) are the coordinates of the antenna 201. As shown in FIG. 34B, this coordinate C is represented by the coordinates of the intersection of the circumference of the circle with the distance Ra centered on the coordinate A and the circumference of the circle with the distance Rb centered on the coordinate B. be able to.

  When two RFID tags are used, two coordinates are normally calculated as the distance Ra from the coordinate A and the distance Rb from the coordinate B. For this reason, one of the coordinates of the intersection is excluded based on conditions such as a room where the reader / writer 202 is arranged. For example, when one of the obtained coordinates is a coordinate outside the room where the reader / writer 202 is arranged, this coordinate cannot be the coordinate C which is the position information of the reader / writer 202. Exclude it.

  Further, here, the case where two RFID tags whose position information is set in advance has been described, but in the present invention, the receiving antenna 4 is used using three or more RFID tags whose position information is set in advance. May be calculated. By using three or more RFID tags, the accuracy of acquiring the position information of the receiving antenna 4 can be improved.

  The position information of each RFID tag 1a, 1b may be transmitted from each RFID tag 1a, 1b, or stored in the information processing apparatus in a state associated with the identification information of each RFID tag 1a, 1b. When the identification information is received from each RFID tag as stored in a medium or the like in advance, the position information corresponding to the received identification information may be acquired from the storage medium.

(Embodiment 4)
The information processing apparatus according to the present embodiment can accurately acquire the position information of the reflector in the information processing apparatus according to the above-described embodiment even when an obstacle exists in the communicable area. Is.

  Hereinafter, a case where the reflector is an RFID tag will be described as an example.

  FIG. 35 is a block diagram showing a configuration of a communication system provided with a reader / writer (information processing apparatus) 203 according to the present embodiment. The configuration of the RFID tag 1 is the same as that shown in FIG.

  The reader / writer 203 includes a transmission antenna 3, a reception antenna 4, a transmission processing unit 5, a reception processing unit 6, a communication control unit 7, a position measurement unit 208, an external communication unit 9, a position determination unit 210, an area information storage unit 211, and a process. Unit 212, failure information storage unit 451, and correction unit 452. Configuration of transmission antenna 3, reception antenna 4, transmission processing unit 5, reception processing unit 6, communication control unit 7, position measurement unit 208, external communication unit 9, position determination unit 210, area information storage unit 211, and processing unit 212 Since this is the same as FIG. 26, the description thereof is omitted.

  The obstacle information storage unit 451 can store obstacle information that is information on obstacles arranged on the communication path between the RFID tag 1 and the receiving antenna 4 of the reader / writer 203. Specifically, the obstacle information storage unit 451 stores information on obstacles arranged in an area where communication is possible. Obstacles here are those that interfere with radio wave communication, specifically those that reflect radio waves, those that absorb or amplify radio waves, and those that output unwanted radio waves. . For example, a wall, ceiling, or floor of a room may be considered as an obstacle. The obstacle information stores, for example, information on elements that affect communication such as the position of the coordinates of the obstacle, the shape, the size, the reflectance, the radio wave absorption rate, and the like. The obstacle information is accumulated in the obstacle information storage unit 451 through a reception unit (not shown), for example. The failure information storage unit 451 is preferably a non-volatile recording medium, but can also be realized by a volatile recording medium.

  The correction unit 452 corrects the position information acquired by the position measurement unit 208 based on the obstacle information stored in the obstacle information storage unit 451. Specifically, the correction unit 452 determines whether or not correction is necessary, and performs correction when it is deemed necessary, and does not perform correction when it is deemed unnecessary. . The correction unit 452 is, for example, an obstacle on a communication path between the RFID tag and the reception processing unit 6, specifically, a path connecting the position indicated by the position information acquired by the position measurement unit 208 and the position of the reception antenna 4. If an object exists, it is determined that correction is necessary. Or the correction | amendment part 452 performs correction | amendment which cancels the content of a change estimated to be received by the obstruction of a communication path, for example. For example, the correction unit 452 determines that there is an obstacle that reflects radio waves on a path connecting the position indicated by the position information indicating the position of the RFID tag 1 acquired by the position measurement unit 208 and the position of the reception antenna 4. In this case, the position information obtained by moving the position information acquired by the position measuring unit 208 symmetrically with the reflecting surface on the obstacle is output as the corrected position information of the RFID tag 1. The correction unit 452 can usually be realized by an MPU, a memory, or the like. The processing procedure of the correction unit 452 is usually realized by software, and the software is recorded in a recording medium such as a ROM. However, it may be realized by hardware (dedicated circuit).

  Next, the operation of the reader / writer 203 will be described using the flowchart of FIG. 36, the same reference numerals as those in FIG. 27 denote the same or corresponding processing steps, and a description thereof will be omitted.

  (Step S3601) The correction unit 452 acquires obstacle information from the obstacle information storage unit 451, and determines whether correction is necessary for the acquired position information in step S2701. For example, when there is an obstacle on the route connecting the position indicated by the position information acquired by the position measurement unit 208 and the position of the receiving antenna 4, the correction unit 452 determines that correction is necessary. For example, as viewed from the receiving antenna 4, the location information indicates that the RFID tag 1 is present in an obstacle that does not normally pass radio waves or in a position beyond the obstacle. This is because it is considered that the light is reflected on the surface or the like and is incident on the receiving antenna 4 from the direction indicated by the position information. For example, the path connecting the position indicated by the position information acquired by the position measurement unit 208 and the position of the receiving antenna 4 can be calculated based on the respective coordinate information. Whether there is an obstacle on the route is obtained by acquiring coordinate information of each obstacle from the obstacle information, and any obstacle exists on the route calculated by the correction unit 452. It can be detected by determining whether or not. If it is determined that correction is necessary, the process proceeds to step S3602, and if correction is not necessary, the process proceeds to step S32702.

  (Step S3602) The correction unit 452 corrects the position information acquired in step S2701 based on the obstacle information. For example, position information when the radio wave is assumed to be reflected on the surface of an obstacle present on the route is calculated. Then, the process proceeds to step S2702.

  Note that the processing is ended by powering off or interruption for aborting the processing in the flowchart in FIG.

  Next, a specific example will be described. The process in which the reader / writer 203 receives a radio wave from the RFID tag 1 and acquires the position information based on the signal received from the RFID tag 1 is the same as in the second embodiment, and thus the description thereof is omitted.

  FIG. 37 is a diagram for explaining the correction processing of the RFID tag position information by the reader / writer 203 according to this embodiment. For example, as shown in FIG. 37, it is assumed that an obstacle 2300 and a floor 2401 that is an obstacle are provided between the receiving antenna 4 of the reader / writer 203 and the RFID tag 1. Here, information such as coordinate information indicating the arrangement of the obstacle 2300 and the floor 2401 and information such as the presence or absence of the property of reflecting the radio waves of the obstacle 2300 and the floor 2401 are stored in advance as obstacle information. Assume that the data is stored in the unit 451. Further, it is assumed that the current position of the RFID tag 1 is present in the area 2310 designated by the area information stored in the area information storage unit 211.

  Here, it is assumed that the position information acquired based on the signal received from the RFID tag 1 is the position A (x1, y1, z1), and the position A specified by the position information from the obstacle information is located in the floor. To do.

  In this case, the correction unit 452 recognizes that the floor 2401 that reflects radio waves exists on the path connecting the position A specified by the position information and the position of the receiving antenna 4 based on the failure information, and the correction is performed. Determine that it is necessary.

  Then, the correction unit 452 calculates the coordinates of a position symmetrical to the point A with respect to the surface of the floor 2401. For example, if the height direction with respect to the floor is the y-axis direction and the floor surface is y = 0, the coordinates of the calculated position are (x1, -y1, z1). And it outputs to the position determination part 210 as the positional information on the RFID tag 1 which correct | amended the value of this coordinate.

  The position determination unit 210 determines that the RFID tag 1 is present at a predetermined position based on the area information and the corrected position information. Other processes are the same as those in the first embodiment, and will not be described.

  As described above, according to the present embodiment, the position information acquired by the position measurement unit 208 is corrected by the information on the obstacle, so that the accuracy of the position detection of the RFID tag is improved and the RFID tag is more accurate. Different actions can be performed depending on the position.

  Note that the configuration for correcting the position information of the RFID tag based on the failure information described in the present embodiment may be applied to the information processing apparatus according to the third embodiment.

  Further, in the present embodiment, on the communication path between the RFID tag and the reception processing unit 6, specifically, on the path connecting the position indicated by the position information acquired by the position measuring unit 208 and the position of the antenna 201. When there is an obstacle, it is determined that correction is necessary and correction is performed. However, if necessary, error correction is performed to indicate that a false detection has been performed without correction. Alternatively, such position information may not be used.

  In the present embodiment, whether or not correction is necessary is determined by determining whether or not there is an obstacle on the communication path. However, in the present invention, an RFID tag cannot exist in advance as failure information. Information for setting the area is prepared, and it is determined whether or not the position of the detected RFID tag is located in an area where it cannot originally exist, and is determined to be located at a position where it cannot originally exist In some cases, it may be determined that correction is necessary.

  In each of the above embodiments, each process (each function) may be realized by centralized processing by a single device (system), or by distributed processing by a plurality of devices. May be.

  Further, in each of the above embodiments, it goes without saying that two or more communication means (such as a transmission unit) existing in one apparatus may be physically realized by one medium.

  The present invention is not limited to the above-described embodiments, and various modifications are possible, and it goes without saying that these are also included in the scope of the present invention.

  The present invention can be modified in various ways within the scope of the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

  An information processing apparatus according to the present invention, a communication system including the information processing apparatus, and the like include, for example, a system for inspecting / confirming the above-described goods, a system for monitoring theft of goods in a store, a station, a movie theater, etc. It is applicable to uses such as a ticket gate system and a keyless entry system installed in a place where a ticket gate is required.

1 is a block diagram showing an outline of a configuration for measuring a distance between an RFID tag and the reader / writer in a reader / writer included in a communication system using the RFID tag according to the present embodiment. It is a block diagram which shows schematic structure of the communication system using the said RFID tag. It is a figure which shows the state in which transmission / reception of a R / W request signal and a tag response signal is performed between a reader / writer and an RFID tag. It is the figure which showed the signal transmitted to a RFID tag from a reader / writer, and its carrier frequency on the time axis. It is the figure which showed the signal transmitted to a reader / writer from an RFID tag, and its carrier frequency on the time axis. It is a block diagram which shows schematic structure of the reader / writer including the specific structure of the reception process part which makes it possible to detect a phase. It is a flowchart which shows the flow of a distance measurement process. It is a flowchart which shows the flow of the distance measurement process using multiple frequencies. It is a flowchart which shows the flow of a frequency selection process and a distance calculation process. It is a figure which shows an example of a frequency selection process typically. It is a figure which shows the state in which multipath has arisen in communication with a reader / writer and an RFID tag. It is a graph which shows the change of the MUSIC evaluation function with respect to distance. It is a figure for demonstrating an arrival direction estimation process. It is a flowchart which shows the first half of the flow of the distance measurement process which applied the MUSIC method. It is a flowchart which shows the second half of the flow of the distance measurement process which applied the MUSIC method. It is the figure which showed the signal transmitted from the reader / writer to the RFID tag and the carrier frequency on the time axis when switching the frequency within one frame. It is the figure which showed on the time-axis the signal transmitted to the reader / writer from the RFID tag, and its carrier frequency in the case of switching the frequency within one frame. It is a flowchart which shows the flow of the distance measurement process accompanied by the frequency switch within 1 frame. It is a block diagram which shows schematic structure of the reader / writer which makes it possible to recognize and recognize each RFID tag and its distance. It is a flowchart which shows the flow of the distance measurement process which identified each RFID tag. It is a figure which shows typically the estimation process of the existing position direction of a RFID tag. It is a block diagram which shows schematic structure of the reader / writer in the case of performing direction calculation. It is a flowchart which shows the first half of the flow of a position estimation process. It is a flowchart which shows the second half of the flow of a position estimation process. It is the figure which showed on the time-axis the signal transmitted to the RFID tag from the reader / writer, and its carrier frequency in the case of simultaneously transmitting a plurality of frequencies within one frame. It is the figure which showed on the time-axis the signal transmitted to the reader / writer from the RFID tag, and its carrier frequency in the case of simultaneously transmitting a plurality of frequencies within one frame. It is a block diagram which shows schematic structure of a reader / writer in the case of simultaneously transmitting a plurality of frequencies within one frame. It is a figure which shows the example at the time of applying the communication system using this RFID tag to the system which test | inspects and confirms the articles | goods distributed. It is a figure which shows the example at the time of applying the communication system using this RFID tag to the system which performs theft monitoring of goods, inventory goods, etc. It is a figure which shows the example of a crime prevention system application which attaches the RFID tag 1 to a window, a door, etc., and detects that this window or door is opened by monitoring the position of this RFID tag 1. For example, it is a figure which shows the example at the time of applying this RFID tag communication system to the place where a ticket gate, such as a station or a movie theater, is required. It is a figure which shows the example at the time of applying the communication system using this RFID tag to keyless entry systems, such as a motor vehicle. It is a block diagram which shows the structure of the reader / writer with which the communication system using the RFID tag which concerns on Embodiment 2 of this invention is provided. It is a flowchart for demonstrating operation | movement of the reader / writer. It is a figure for demonstrating the operation | movement of the position determination of the reader / writer. It is a figure for demonstrating the operation | movement of the position determination of the reader / writer. It is a figure for demonstrating the specific example. It is a block diagram which shows the structure of the reader / writer with which the communication system using the RFID tag which concerns on Embodiment 3 of this invention is provided. It is a flowchart for demonstrating operation | movement of the reader / writer. It is a figure for demonstrating the specific example. (A) The figure for demonstrating the process which measures the distance of the receiving antenna and the tag whose position information is known, (b) The figure for demonstrating the process which detects the position of the receiving antenna. It is a block diagram which shows the structure of the reader / writer with which the communication system using the RFID tag which concerns on Embodiment 4 of this invention is provided. It is a flowchart for demonstrating operation | movement of the reader / writer. It is a figure for demonstrating the specific example. It is a block diagram which shows the structure of the RF communication system of a prior art. It is a block diagram which shows the structure of the communication apparatus which performs radio | wireless communication with the RFID tag of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b RFID tag 2 Reader / writer 3 Transmitting antenna 4 Receiving antenna 4A 1st antenna element 4B 2nd antenna element 5 Transmission processing part 5A PLL part 5B Modulation part 5C Power amplification part 6 Reception processing part 6A, 6A1, 6A2 Amplification Unit 6B frequency conversion unit 6B1 and 6B2 mixer 6B3 90 ° phase shift unit 6C preamble extraction unit 6D selector 7 communication control unit 7A frequency control unit 7B transmission control unit 7C reception control unit 8, 208 position measurement unit 8A phase information acquisition unit 8B distance Calculation unit 8C Direction calculation unit 9 External communication unit 10 Area determination unit 11, 211 Area information storage unit 70 Luggage sorting system 77 Sorting device 200, 202 Information processing device (reader / writer)
208C Position information acquisition unit 210, 411 Position determination unit 212 Processing unit 410 Local position information acquisition unit 451 Fault information storage unit 452 Correction unit

Claims (36)

Transmitting means for transmitting a request signal, which is a signal composed of one frame, by radio waves of one carrier frequency having a plurality of different carrier frequency components;
Receiving means for receiving, via an antenna, a reflected signal, which is a signal consisting of one frame, generated by the request signal transmitted by the transmitting means being reflected while being subjected to predetermined modulation by a reflector;
A phase information acquisition unit that calculates the amount of change in phase between the reflected signal received by the receiving unit and the request signal for each carrier frequency component transmitted by the transmitting unit;
A distance calculation unit that calculates a distance between the antenna and the reflector based on a phase change amount and a carrier frequency component for each carrier frequency component acquired by the phase information acquisition unit;
A position information acquisition unit that acquires position information that is information related to the position of the reflector, based on the distance calculated by the distance calculation unit;
A position determination unit that determines whether or not the reflector exists at a predetermined position based on the position information acquired by the position information acquisition unit, and outputs a determination result;
An information processing apparatus comprising: a processing unit that performs predetermined processing based on the determination result. The receiving means receives the reflected signal through a plurality of antennas, respectively.
The phase information acquisition unit calculates the amount of change in phase for each reflected signal received via the plurality of antennas,
The distance calculating unit calculates distances between the plurality of antennas and the reflectors based on the amount of change in the phase calculated for each reflected signal respectively received through the plurality of antennas. ,
The information processing apparatus according to claim 1, wherein the position information acquisition unit acquires position information of the reflector based on distances between the plurality of antennas and the reflector. An area information storage unit that stores area information that is information about the predetermined area;
The position determination unit determines whether or not the reflector is arranged at the predetermined position by comparing the position information acquired by the position information acquisition unit and the area information. The information processing apparatus according to claim 1, wherein The information processing apparatus further includes a self-location information acquisition unit that acquires self-location information that is information related to a position of the device.
The position determination unit determines whether the position information acquired by the position information acquisition unit and the own position information satisfy a predetermined relationship, so that the reflector is arranged at the predetermined position. The information processing apparatus according to claim 1, wherein a determination result is acquired by determining whether or not the information is present. The information processing apparatus according to claim 1, wherein the processing unit outputs a reflected signal received by the receiving unit when the determination result indicates that the reflector is present at the predetermined position. The information processing apparatus according to claim 1, wherein the processing unit transmits predetermined information to the reflector when the determination result indicates that the reflector is present at the predetermined position. The information processing apparatus according to claim 1, wherein the processing unit outputs a control signal for controlling communication with the reflector based on the determination result. An obstacle information storage unit capable of storing obstacle information, which is information of an obstacle arranged in a communication path between the reflector and the antenna;
A correction unit that corrects the position information of the reflector based on the obstacle information;
The information processing apparatus according to claim 1, wherein the position determination unit determines whether the reflector is present at a predetermined position based on the position information corrected by the correction unit, and acquires a determination result.   The information processing apparatus according to claim 1, wherein the transmission unit sets a plurality of divided periods within a period in which one request signal is transmitted, and controls the carrier frequencies to be different from each other in each divided period. A reflected signal is transmitted from the reflector by radio waves of carrier frequencies having three or more carrier frequency components different from each other,
The phase information acquisition unit acquires a phase change amount by selecting two carrier frequency component signals that satisfy a predetermined criterion in calculating the distance from the signal of each carrier frequency component. The information processing apparatus according to claim 1. The receiving means includes
A frequency conversion unit that performs frequency conversion processing of the received reflected signal is provided.
The information processing apparatus according to claim 1, wherein the frequency conversion unit converts the reflected signal into an I signal and a Q signal.   The information processing apparatus according to claim 1, wherein the distance calculation unit calculates the distance using a high resolution spectrum analysis method.   The distance calculation unit uses a MUSIC (Multiple Signal Classification) method as the high-resolution spectrum analysis method, uses reflection signals received at a plurality of different carrier frequencies as an input of the MUSIC method, and uses a mode vector as the distance The information processing apparatus according to claim 12, wherein a MUSIC evaluation function is obtained as a function of and the distance is calculated by obtaining a peak value of the MUSIC evaluation function.   The information processing apparatus according to claim 1, wherein the distance calculation unit calculates the distance by using reception intensity of the received reflected signal together.   2. The reception control unit according to claim 1, further comprising: a reception control unit that acquires information on the data part included in the reflected signal and outputs the distance information calculated by the distance calculation unit and the information on the data unit in an external manner. Information processing device.   The information processing apparatus according to claim 1, wherein the distance calculation unit measures a direction in which a reflector that has transmitted the reflection signal is located based on the reflection signal.   The information processing apparatus according to claim 1, wherein the distance calculation unit calculates the distance by analyzing a signal in a preamble part of the reflected signal. An information processing apparatus according to any one of claims 1 to 17,
A communication system comprising: at least one reflector that performs wireless communication with the information processing apparatus. An information processing apparatus according to any one of claims 1 to 17,
A communication system comprising: a management device that manages at least one of an article, a person, and a living thing associated with the reflector based on a result of communication with the reflector performed by the information processing device . A transmission step of transmitting a request signal, which is a signal composed of one frame, by radio waves of one carrier frequency having a plurality of different carrier frequency components;
A receiving step of receiving, via an antenna, a reflected signal, which is a signal composed of one frame, generated by the request signal transmitted in the transmitting step being reflected while being subjected to predetermined modulation by a reflector;
A phase information acquisition step of calculating, for each carrier frequency component transmitted by the transmission unit, a phase change amount between the reflected signal received in the reception step and the request signal;
A distance calculating step of calculating a distance between the antenna and the reflector based on a phase change amount and a carrier frequency component for each carrier frequency component acquired by the phase information acquiring step;
Based on the distance calculated in the distance calculation step, a position information acquisition step for acquiring position information that is information related to the position of the reflector;
A position determination step of determining whether or not the reflector is present at a predetermined position based on the position information acquired in the position information acquisition step, and outputting a determination result;
A processing step of performing predetermined processing based on the determination result. The receiving step receives the reflected signals through a plurality of antennas, respectively.
The phase information acquisition step calculates the amount of change of the phase for each reflected signal received via the plurality of antennas,
The distance calculating step calculates distances between the plurality of antennas and the reflectors based on a change amount of the phase calculated for each reflected signal respectively received through the plurality of antennas. ,
The information processing method according to claim 20, wherein the position information acquisition step acquires position information of the reflector based on a distance between the plurality of antennas and the reflector. The position determination step compares the position information acquired in the position information acquisition step with area information that is information about a predetermined area stored, so that the reflector is arranged at the predetermined position. The information processing method according to claim 20, wherein it is determined whether the determination is made and a determination result is obtained. A self-location information acquisition step of acquiring self-location information, which is information relating to a position for performing the process of acquiring the location information,
The position determination step determines whether or not the position information acquired in the position information acquisition step and the own position information satisfy a predetermined relationship, whereby the reflector is arranged at the predetermined position. 21. The information processing method according to claim 20, wherein a determination result is obtained by determining whether or not the information is present. 21. The information processing method according to claim 20, wherein the processing step outputs the reflected signal received in the receiving step when the determination result indicates that the reflector is present at the predetermined position. 21. The information processing method according to claim 20, wherein the processing step transmits predetermined information to the reflector when the determination result indicates that the reflector is present at the predetermined position. The information processing method according to claim 20, wherein the processing step outputs a control signal for controlling communication with the reflector based on the determination result. A correction step of correcting position information of the reflector based on obstacle information that is information of an obstacle arranged in a communication path between the reflector and the antenna before;
The information processing method according to claim 20, wherein the position determination step determines whether or not the reflector is present at a predetermined position based on the position information corrected in the correction step, and acquires a determination result.   21. The information processing method according to claim 20, wherein the transmission step sets a plurality of divided periods within a period in which one request signal is transmitted, and controls the carrier frequencies to be different from each other in each divided period. A reflected signal is transmitted from the reflector by radio waves of carrier frequencies having three or more carrier frequency components different from each other,
The phase information acquisition step selects two carrier frequency component signals that satisfy a predetermined criterion in calculating the distance from the signals of the respective carrier frequency components, and acquires a phase change amount. The information processing method according to claim 20. The receiving step includes
A frequency conversion step for performing frequency conversion processing of the received reflected signal;
The information processing method according to claim 20, wherein in the frequency conversion step, the reflected signal is converted into an I signal and a Q signal.   21. The information processing method according to claim 20, wherein the distance calculating step calculates the distance using a high resolution spectrum analysis method.   The distance calculating step uses a MUSIC method as the high resolution spectrum analysis method, uses reflected signals received at a plurality of different carrier frequencies as inputs of the MUSIC method, and uses a mode vector as a function of the distance to evaluate MUSIC 32. The information processing method according to claim 31, wherein the distance is calculated by obtaining a function and obtaining a peak value of the MUSIC evaluation function.   21. The information processing method according to claim 20, wherein the distance calculating step calculates the distance by using the received intensity of the received reflected signal together.   21. The reception control step according to claim 20, further comprising: obtaining a data portion information included in the reflected signal, and combining the distance information calculated in the distance calculation step with the data portion information and outputting the information to the outside. Information processing method.   21. The information processing method according to claim 20, wherein the distance calculating step measures a direction in which a reflector that has transmitted the reflection signal is located based on the reflection signal.   The information processing method according to claim 20, wherein the distance calculating step calculates the distance by analyzing a signal in a preamble portion of the reflected signal.

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