JP2004289330A - Communication method by contactless method, communication system, external apparatus, and rf id tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication method and a communication system adopting a contactless method capable of stably supplying power and to provide an external apparatus or an RF ID tag used for the communication system. <P>SOLUTION: The communication method is a method whereby the RF ID tag 10 with an antenna coil 11 and a reader / writer 20 for transmitting data to the RF ID tag 10 carry out data communication by the contactless method. The method includes the steps of: generating a modulation waveform corresponding to a value of data by each of 2-bit data; generating a carrier signal; modulating the carrier signal on the basis of the modulation waveform to generate a transmission signal; transmitting the transmission signal to the tag; and generating power on the basis of the transmission signal by the RF ID tag 10. When data are 00 in the step of generating the modulation waveform, the modulation waveform of #1 logic '00' or #2 logic '00' is generated. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a non-contact communication method and communication system, and an RFID tag and an external device used in the communication system.
[0002]
[Prior art]
Radio frequency identification (RFID) systems are used to identify and check the movement of machines, inventory or living things. This RFID system manages an RFID tag having an antenna coil and a memory, a reader / writer module for reading information from the antenna coil and the RFID tag, and writing information to the RFID tag, and information about the reader / writer module. It is composed of a host computer and the like. The RFID tag stores predetermined information such as the type of a product, and is attached to, for example, a product as a data carrier, and the host computer manages inventory information and the like. Since communication between the RFID tag and the reader / writer is performed by a non-contact method using an antenna coil, the risk of failure due to contact deterioration and mechanical stress can be reduced. This RFID tag is used as a non-contact type IC card, and is used for product management and the like.
[0003]
An ASK method is used as a communication method between the RFID tag and the reader / writer (for example, Patent Document 1, Patent Document 2, and Patent Document 3). By using ASK modulation, it is possible to suppress a decrease in communication sensitivity due to a frequency shift caused by the effect of the conductive member of the antenna coil. An example of a communication method using the ASK method in the RFID system will be described below.
[0004]
The data transmitted / received by the RFID system is composed of, for example, 9-byte command information and 2-byte CRC data used for error checking. The data transmitted / received at one time is defined as data of one frame. At the time of writing, the command information and the like are stored in a memory provided in the RFID tag. At the time of writing, the data of one frame is amplitude-modulated and transmitted from the reader / writer to the RFID tag.
FIG. 5 is a diagram showing a signal waveform for modulating a carrier by a conventional communication method. In order to perform modulation based on 2-bit data, four types of waveforms shown in FIG. 5 are prepared according to data values. Here, the 2-bit data of 00 is represented by a waveform of logic “00”. Similarly, 2-bit data 01, 10, and 11 are represented by waveforms of logic “01”, logic “10”, and logic “11”. The four types of 2-bit data are represented by four different types of 9.44 μsec waveforms. This time is defined as a unit modulation section. For example, in the waveform of logic "00", the signal becomes H for the first 1.18 .mu.sec, and becomes L for the next 1.18 .mu.sec. Then, the remaining 5.9 μsec becomes H.
As shown in FIG. 5, the time during which the signal is at the L level is 1.18 μsec in any of the waveforms of the logic “00”, the logic “01”, the logic “10”, and the logic “11”. The timing changes from H to L at 1.18 μsec, 3.54 μsec, 5.90 μsec, and 8.26 μsec from the beginning of the unit modulation section. The four types of waveforms represent 2-bit data. A continuous waveform of the unit modulation section is generated according to one frame of data to be transmitted. For example, in the data following 0011, a waveform in which a waveform of logic “00” and a waveform of logic “11” are continuous is generated. Thus, the waveform based on the 2-bit data represents one frame of data consisting of a plurality of bytes. In the RFID tag, 2-bit data is distinguished based on this waveform, so that transmission and reception of data of a plurality of bytes can be performed.
[0005]
At the time of transmitting a signal from the reader / writer to the RFID tag, since the ASK method is used, the carrier signal is modulated by a signal having a continuous waveform in the unit modulation section described above. A 13.56 MHz sine wave is used for the carrier signal. Therefore, a signal with a 13.56 MHz sine wave carrier is output. In other words, the carrier does not ride while the waveform is at the L level, and the carrier rides only while the waveform is at the H level. FIG. 6 shows an example of the output of the transmitted and received signals. FIG. 6 is a diagram showing an output signal of a portion where 11 data and 00 data are continuous. In FIG. 6, the upper part shows a modulation waveform in which 11 and 00 are continuous, and the lower part shows the waveform of an output signal with a carrier. Since the wave height (level) is L in the portion A and the portion C, the carrier is cut off. In the portion before A, the portion in B, and the portion after C, the carrier is on because it is at the H level. Therefore, the carrier is transmitted in the part before A, the part in B, and the part after C, and no carrier is transmitted in the part in A and the part in C. The time during which no carrier is transmitted is referred to as a carrier OFF time, and the time during which a carrier is transmitted is referred to as a carrier ON time.
[0006]
The carrier ON time is measured based on the transmitted signal, and data recognition is performed based on the measured time. Specifically, since the length of the carrier ON time differs depending on each data and the order thereof, the waveform is detected based on the number of carriers included in one carrier ON time. It is sequentially determined whether the waveform of the unit modulation section corresponds to any one of # 1logic "00" to logic "11", and data for one frame is recognized. When writing data, the RFID tag stores the recognized data in the memory.
[0007]
When such a communication method is used, there are the following problems. The RFID tag usually generates power by a carrier transmitted from a reader / writer and supplies power to a memory or the like. Specifically, the carrier of the signal transmitted from the antenna coil of the reader / writer is received by the antenna coil provided in the RFID tag. A power supply is generated using a signal received by the antenna coil of the RFID tag. Memory rewriting and the like are performed using this power supply. Therefore, it is desirable to make the carrier ON time as long as possible. If the carrier ON time is short, power is not supplied stably, and writing to the memory may not be performed.
[0008]
In particular, when the data is continuous with 11:00, the carrier OFF time (A), the carrier ON time (B), and the carrier OFF time are switched with a time width of 1.18 μsec when switching from the section 11 to the section 00 as shown in FIG. Time (C) is continuous. In this case, the carrier is transmitted for only 1/3 of 1.18 μsec during 3.54 μsec, and the power cannot be supplied stably. Such a decrease in the carrier ON time causes an RFID reset. Of course, the above-described waveform for modulation is an example, and therefore, the carrier OFF time is not necessarily shortened when data continues to 11:00, but certain two data may be continuous depending on the combination of the waveforms for modulation. In this case, the carrier ON time always becomes short.
[0009]
To solve this problem, it is conceivable to change the waveform for modulation. For example, it is conceivable that the time when the waveform of logic “00” becomes L is later or the time when the waveform of logic “11” is L is earlier. However, when the position of L overlaps or approaches another waveform, the 2-bit data may be erroneously recognized. Therefore, the position of L needs to be separated to some extent between the four types of waveforms, and ideally, it is desirable to arrange the positions of L level uniformly within the unit modulation section. Further, it is conceivable to shorten the time of L of the modulation waveform, but there is a limit from the viewpoint of erroneous recognition of data. Further, when the unit modulation section is shortened from the viewpoint of the communication speed, the carrier ON time is further shortened. Therefore, it has been difficult to stably supply power to the RFID tag by the conventional communication method.
[0010]
[Patent Document 1]
JP 2002-208876 A
[Patent Document 2]
JP-A-2002-157568
[Patent Document 3]
JP-A-2002-366908
[0011]
[Problems to be solved by the invention]
As described above, the conventional communication method has a problem that power cannot be stably supplied to the tag.
[0012]
SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and a non-contact communication method and communication system capable of stably supplying power, an external device and an RFID tag used in the communication system The purpose is to provide.
[0013]
[Means for Solving the Problems]
The communication system according to the present invention is a communication method in which data communication is performed in a non-contact manner by a tag having an antenna and an external device transmitting data to the tag, wherein the transmission data is n bits (n is 1). Generating a modulation waveform corresponding to the value of the n-bit data, generating a carrier signal, modulating the carrier signal based on the modulation waveform, Generating a transmission signal, transmitting the transmission signal to the tag, and generating a power source based on the transmission signal, the tag generating the modulation waveform. Is determined to be a first value (for example, 00 in the present embodiment), and if the data is the first value, a first modulation waveform (for example, # 2Logic "00") or the second modulation waveform in state (e.g., # 1logic in this embodiment "00") in which is generated. Thereby, power can be stably supplied to the tag.
[0014]
In the above-described communication method, it is preferable that a second modulation waveform is generated at a first value immediately after a value other than the first value. Thereby, power can be stably supplied to the tag.
In a preferred embodiment of the above-mentioned communication method, the modulation waveform has two levels, that is, an H level and an L level, and changes to an L level at different timings depending on the value of the n-bit data.
[0015]
A communication method according to the present invention is characterized in that, in the transmission signal of the communication method described above, no carrier is transmitted while the modulation waveform corresponds to the L level.
[0016]
In the communication method described above, the first modulation waveform is a waveform having the earliest timing of L level as compared with a modulation waveform corresponding to a value other than the first value, and the first modulation waveform is the first signal in the transmission data. It is desirable that the second modulation waveform be used for the first value immediately after the value other than the value. Thereby, power can be stably supplied to the tag.
[0017]
In the above communication method, it is desirable that the second modulation waveform is a waveform that does not become L level. Thereby, power can be more stably supplied to the tag.
[0018]
The preferred embodiment of the communication method described above is one that is modulated by the ASK method.
[0019]
The communication system according to the present invention includes a tag (for example, the RFID tag 10 in the present embodiment) having an antenna (for example, the antenna coil 11 in the present embodiment) and an external device that transmits data to the tag by a non-contact method. In a communication system including (for example, the reader / writer 20 in the present embodiment), the tag generates a power based on a signal transmitted from the external device. A power generation circuit 12); and a storage unit (for example, the memory 13 in the present embodiment) that stores information based on the data by the power generated by the power generation unit. The data is transferred to the L register at different timings depending on the value of the n-bit data for each n-bit data (n is an integer of 1 or more) A modulation waveform generator (for example, the controller 21 in the present embodiment) that generates a modulation waveform that becomes a signal, and a transmission signal generator (for example, this embodiment) that generates a transmission signal based on the modulation waveform. And a transmitting unit (for example, the antenna coil 23 in the present embodiment) for transmitting the transmission signal, and the first value of the n-bit data value is the first value. Two or more different modulation waveforms having a modulation waveform and a second modulation waveform are associated with each other. Thereby, power can be stably supplied to the tag.
[0020]
In a preferred embodiment of the communication system described above, the tag is an RFID tag.
[0021]
In the communication system described above, the first modulation waveform is a waveform having the earliest timing of L level compared to a modulation waveform corresponding to a value other than the first value. It is desirable that the second modulation waveform be used for the first value immediately after the value other than the value. Thereby, power can be stably supplied to the tag.
[0022]
In the above communication system, it is desirable that the second modulation waveform is a waveform that does not become L level. Thereby, power can be stably supplied to the tag.
[0023]
An external device according to the present invention includes an antenna for receiving a signal, and transmits data to an RFID tag that generates power based on a signal received by the antenna. a modulation waveform generator that generates a modulation waveform corresponding to the value of the n-bit data for each data of (n is an integer of 1 or more), and a transmission signal generator that generates a transmission signal based on the modulation waveform And a transmission unit for transmitting the transmission signal, wherein when the value of the n-bit data is a first value, the modulation waveform generation unit outputs the first modulation waveform or the second modulation waveform. To generate a waveform for use.
[0024]
In the above-described external device, the first modulation waveform is a waveform having the earliest timing of L level as compared with a modulation waveform corresponding to a value other than the first value, and the first modulation waveform is the first waveform in the transmission data. It is desirable that the second modulation waveform be used for a first value immediately after a value other than the value of.
[0025]
According to the RFID tag of the present invention, a signal obtained by modulating one frame of data for each n-bit (n is an integer of 1 or more) data by a modulation waveform corresponding to the value of the n-bit data is provided in a non-contact manner. An RFID tag for receiving the signal, a receiving unit for receiving the signal, a power generation unit for generating power based on the received signal, and power supplied by the power generation unit, the received signal A memory for storing data based on the data, a demodulator for demodulating the signal and detecting the modulation waveform (for example, the control circuit 14 in the present embodiment), and a power supply generated by the power generator. A control unit for recording data based on the modulation waveform in the memory, wherein the control unit recognizes two different modulation waveforms as data having the same value. It is intended to. Thereby, power supply can be performed stably.
[0026]
In the above-described RFID tag, it is desirable that one of the two different modulation waveforms is the waveform with the earliest timing of L level. Thereby, power supply can be performed stably.
[0027]
In the above-described RFID tag, it is preferable that the other of the two different modulation waveforms is a waveform that does not become L level. Thereby, power supply can be performed stably.
[0028]
In a preferred embodiment of the above-described RFID tag, the carrier of the signal is turned off when the waveform for modulation corresponds to the L level, and the demodulation unit detects the waveform for modulation based on the time when the carrier of the signal is turned off. Things.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment of the Invention
A communication method using the RFID tag according to the present embodiment will be described. FIG. 1 is a configuration diagram showing an example of the RFID system. 10 is an RFID tag, 11 is an antenna coil, 12 is a power generation unit, 13 is a memory, 14 is a control circuit, 20 is a reader / writer, 21 is a controller, 22 is a transceiver / receiver, 23 is an antenna coil, and 30 is a host. is there.
[0030]
Signals are transmitted and received between the RFID tag 10 and the reader / writer 20 by the antenna coil 11 and the antenna coil 23, and data is communicated. The host 30 and the reader / writer 20 are connected by a USB cable, a UART cable, or the like. The information read from the RFID tag 10 to the reader / writer 20 is transmitted to the host 30. The host 30 is an ordinary computer or industrial equipment, and can store information received from the reader / writer 20. Further, the host 30 can transmit a command for rewriting information stored in the RFID tag 10 to the reader / writer 20. Based on this command, the reader / writer 20 generates and outputs a transmission signal and writes information to the RFID tag 10. Since the RFID tag 10 is attached to, for example, each product, the host 30 can perform product management and the like. Alternatively, by using the RFID tag 10 as an IC card, human identification or the like can be performed. As described above, the communication system using the RFID tag 10 can identify a machine, a stock, or a living thing, and can check the movement. It is assumed that the RFID tag 10 stores predetermined information and includes a data carrier on which the information is rewritten.
[0031]
The reader / writer 20 includes a controller 21, a transceiver / receiver 22, and an antenna coil 23. The controller 21 is configured by a microcomputer such as an ASIC. The transceiver / receiver 22 includes a modulator, a demodulator, and the like. When receiving a write command to the RFID tag 10 from the host 30, the controller 21 generates a modulation waveform based on the command information data. The transceiver / receiver 22 modulates the carrier based on the waveform for modulation to generate a transmission signal, and outputs the signal via the antenna coil 23. When reading the data of the RFID tag 10, the signal received by the antenna coil 23 is demodulated by the transceiver / receiver 22. The controller 21 recognizes the data based on the demodulated signal and transmits the data to the host 30.
[0032]
The RFID tag 10 includes an antenna coil 11, a power generation unit 12, a memory 13, and a control circuit 14. For the RFID tag 10, a coil-on-chip in which an antenna is formed on a semiconductor chip is used. Further, the power generation unit 12, the memory 13, and the control circuit 14 can be formed on the same chip. The antenna coil 11 is formed of a spiral conductor layer formed on a semiconductor chip. The antenna coil 11 can be formed by subjecting a semiconductor wafer to lithography, vapor deposition, sputtering, plating, and the like. Since the antenna coil 11 can be formed by a method similar to a conventional manufacturing method, a detailed description will be omitted.
[0033]
When the host 30 issues a command to write data to the RFID tag 10, the signal output by the reader / writer 20 is received by the antenna coil 11. The antenna coil 11 is connected to the power generation unit 12. The power generation unit 12 rectifies the received signal with an AC / DC converter or the like, and supplies this current to the memory 13 and the control circuit 14. Thereby, power for driving the memory 13 and the control circuit 14 is supplied. The control circuit 14 can demodulate the signal received by the antenna coil 11 and store it in the memory 13. The memory 13 includes a ROM, a RAM, an EEPROM, and / or an FRAM for storing data. Data based on product information and the like is stored in this memory. The control circuit 14 includes a CPU and the like.
[0034]
When reading data, a signal is transmitted from the RFID tag 10 to the reader / writer 20. In this case, the information stored in the memory 13 is modulated by the control circuit 14. The modulated signal is transmitted to the reader / writer 20 via the antenna coil 11. The reader / writer 20 receives a signal through the antenna coil 23, and the signal is demodulated by the transceiver / receiver 22. The controller 21 recognizes the data based on the demodulated signal and transmits the data to the host 30.
[0035]
Data transmitted in the communication system using the RFID tag 10 includes, for example, 9-byte command information and 2-byte CRC data used for error checking. The data transmitted / received at one time is defined as data of one frame. At the time of writing, this command information is stored in a memory provided in the RFID tag. The data of this one frame is subjected to amplitude displacement modulation (ASK modulation) and transmitted and received.
[0036]
FIG. 2 shows an example of a signal waveform generated by the controller 21 of the reader / writer 20 at the time of writing. FIG. 2 is a diagram showing a modulation waveform corresponding to a value (00, 01, 10, 11) of 2-bit data for modulating a carrier signal. In the conventional communication method, four types of waveforms corresponding to 2-bit data are prepared. In the present embodiment, five types of modulation waveforms are prepared. Here, data having a value of 00 is represented by a waveform of logic “00”. Similarly, data of 01, 10, and 11 are represented by a waveform of logic “01”, a waveform of logic “10”, and a waveform of logic “11”. Further, two types of waveforms indicating data of 00 are prepared in advance. These two waveforms are a # 1logic "00" waveform and a # 2logic "00" waveform. These are represented by different 9.44 μsec waveforms. This time is defined as a unit modulation section. The waveform in this unit modulation section is defined as a modulation waveform. A 2-bit signal is distinguished by the type of the modulation waveform. Since 2-bit data is transmitted at 9.44 μsec, the transmission time of 1-bit data is 4.72 μsec.
[0037]
For example, in the modulation waveform of # 2logic “00”, the wave height (level) is H (High) during the first 1.18 μsec, and L (Low) during the next 1.18 μsec. Then, the remaining 5.9 μsec becomes H. As shown in FIG. 2, the time during which the amplitude is at the L level is 1.18 μsec in any of the waveforms of # 2logic “00”, logic “01”, logic “10”, and logic “11”. The timing of changing to L is different, and the level changes from H level to L level at 1.18 μsec, 3.54 μsec, 5.90 μsec, and 8.26 μsec from the start of the unit modulation section. Further, in the modulation waveform of # 1logic “00”, there is no time to become L, and it remains constant at H level during the unit modulation section (9.44 μsec). The five waveforms represent 2-bit data. A continuous waveform of the unit modulation section is generated according to the transmitted data of a plurality of bytes. For example, when the data to be transmitted is 11, 10, the modulation waveform of logic "11" and the modulation waveform of logic "10" are continuous. The signal waveform having the continuous modulation waveform represents one frame of data composed of a plurality of bytes. In the RFID tag, one frame of data is distinguished based on the continuous waveform, so that a plurality of bytes of data can be written.
[0038]
At the time of writing data from the reader / writer 20 to the RFID tag 10, a signal in which a carrier is put on a waveform in which the above-described modulation waveform is continuous is transmitted. A sine wave having a clock frequency (fc) of 13.56 MHz is used as the carrier signal. Therefore, the carrier is modulated by the modulation waveform, and the carrier does not ride while the carrier is at the L level, and the carrier rides only while the carrier is at the H level. The output of the transmitted / received signal is as shown in FIG. FIG. 3 is a diagram showing output signals of portions where data values are 11, 00, and 00. Actually, such an output signal is generated for one frame of data. The upper part of FIG. 3 shows a continuous waveform based on the data of 11, 00, 00, and the lower part shows an output signal in which a 13.56 MHz carrier is put on the continuous waveform. Although 128 carriers actually occupy the unit modulation section, the number of carriers is smaller than the actual number for explanation. In the portion of L, the carrier is cut off in the output waveform. This time is referred to as a carrier OFF time. At the H level, the carrier is on. This time is defined as the carrier ON time. The carrier is transmitted during the carrier ON time, and the carrier is not transmitted during the carrier OFF time. This modulation is performed by the transceiver / receiver 22.
[0039]
Then, the control circuit 14 measures the carrier ON time (data edge interval) based on the transmitted signal, and performs data recognition based on the measured time. Specifically, since the length of the carrier ON time differs depending on the order of each data, the modulation waveform is detected based on the number of carriers (the number of 13.56 MHz sine waves) included in one carrier ON time. I do. It is sequentially determined whether the waveform of the unit modulation section corresponds to any one of # 1logic "00" to logic "11", and data for one frame is recognized. The recognized data is recorded in the memory 13. The control circuit 14 thus demodulates the signal and recognizes the data.
[0040]
In this embodiment, in order to lengthen the carrier ON time, a modulation waveform of # 1logic "00" which is fixed at the H level and does not become the L level is used. When a carrier is placed using such a waveform, an unmodulated output signal is generated. The modulation waveform of # 1logic “00” is generated when data of 00 continues after data of any of 11, 10, and 01. For example, if there is 00 data immediately after 11 data, the modulation waveform of # 1logic “00” is continuous. This results in the state shown in FIG.
[0041]
Conventionally, when switching from the waveform 11 to the waveform 00, the level is continuous from L → H → L at an interval of 1.18 μsec, but in the present embodiment, a # 1logic “00” modulation waveform is used. Therefore, during the unit modulation section corresponding to data 00 after the L level, the signal does not go to the L level but remains at the H level. As described above, the control circuit 14 recognizes the 00 data also in the case of the waveform which remains at the H level during the unit modulation section. In this embodiment, # 2logic has the fastest L-level timing as compared to the modulation waveforms (logic "01", logic "10", and logic "11") corresponding to the other data (01, 10, 11). Two types of waveforms, “00” and # 1logic “00” fixed at the H level, are made to correspond to 00 data.
This makes it possible to extend the carrier ON time by a certain amount of time even when data switches from 11 at the latest L level to 00 at the earliest L level. By continuing the modulation waveform of # 1logic “00” after the modulation waveform of logic “11”, power for recording data to the memory can be supplied stably. Further, resetting of the RFID tag 10 can be prevented.
[0042]
On the other hand, when the data of 00 is repeated twice or more, the modulation waveform of # 2logic “00” is used as the second and subsequent waveforms. As a result, as shown in FIG. 3, the modulation waveform of # 2logic "00" is used after the modulation waveform of # 1logic "00". If the modulation waveform of # 1logic "00" represents data that is continuous with 00 without using # 2logic "00", the modulation waveform of # 1logic "00" has no time to become L. The H level continues for a time corresponding to the data number of 00. In this case, the carrier ON time can be lengthened, but the carrier OFF time is lost.
[0043]
By the way, the RFID tag 10 recognizes which part of the continuous waveform corresponds to one unit modulation section by the number of carriers. That is, when a certain number of carriers (a number determined by the clock frequency, the unit modulation section, and the modulation waveform) arrive, that part is recognized as the unit modulation section corresponding to one data. However, since the number of carriers may shift depending on the communication environment, communication distance, and the like, the deviation of the number of carriers is corrected based on the carrier OFF time. As a result, the unit modulation section corresponding to each data is accurately recognized, and the consistency between the clock and the data can be obtained. That is, since the timing at which the carrier is turned off is stored in advance for each waveform, the clock and data can be matched for each data by the carrier off time. In this way, erroneous recognition of data is prevented.
[0044]
When only the modulation waveform of # 1logic "00" is used, there is no carrier OFF time, so that correction cannot be performed, and deviations accumulate. Therefore, if the 00 data is continuous, the data will be erroneously recognized due to accumulation. However, by using two types of waveforms for the data of 00 as in the present embodiment, the carrier OFF time occurs even when the data of 00 is continuous, so that the deviation can be corrected. Thereby, the consistency between the clock and the data can be obtained.
[0045]
As described above, in the present embodiment, when any one of data 01, 10, and 11 becomes data 00, a modulation waveform of # 1logic "00" is generated. If the data of 00 continues, a modulation waveform of # 2logic “00” is generated for the second and subsequent data. Then, any of the modulation waveform of # 1logic “00” or the modulation waveform of # 2logic “00” can be recognized as 00 data. The generation of these two types of waveforms is performed by the controller 21 of the reader / writer 20. Hereinafter, a flow for generating these two types of waveforms will be described with reference to FIG.
[0046]
FIG. 4 is a flowchart for generating a modulation waveform. The generation of the modulation waveform is performed on the transmission data to the RFID tag 10. The controller 21 sequentially generates a modulation waveform for one frame based on the value of each 2-bit data. First, it is determined whether or not the value of the 2-bit data is 00. If the data is not 00, it is sequentially determined whether the data is data of 01, 10, and 11, and a waveform (modulation waveform of logical "01", logical "10", or logical "11") corresponding to each data is generated. Is done. If the data is not 00, the 00 consecutive flag is set to 0. Based on the 00 continuation flag, it is determined whether 00 is continuous.
[0047]
If the data is 00, it is determined whether 00 is continuous based on the 00 continuation flag. When the immediately preceding data is 01, 10, or 11, the flag is 1 as described above. Therefore, when the flag is 0, it is determined that 00 is not continuous, and a 00 unmodulated waveform (# 1logic “00”) is generated. At this time, the flag is set to 1. On the other hand, if the immediately preceding data is 00, the 00 modulation waveform (# 2logic “00”) is generated because the 00 consecutive flag is 1 as described above in the processing of the previous data. In this way, the waveforms corresponding to the two types of 00 data are determined and generated.
[0048]
When data other than 00 comes after data having 00 consecutive, the 00 consecutive flag is set to 0 as described above. Therefore, even if the data of 00 comes again after the data other than 00, the data of 00 immediately after generates a 00 non-modulated waveform (# 1logic “00”). For 00 data after the second time, a 00 modulation waveform (# 2logic “00”) is generated. By repeating such a process, a continuous waveform based on one frame of data can be generated. Then, the signal is modulated based on the continuous waveform and transmitted.
[0049]
As described above, in the present embodiment, a waveform having no further L is prepared for data (00) corresponding to a modulation waveform that becomes L level at the earliest timing as compared with modulation waveforms corresponding to other values. ing. When the data (00) comes after the other data (11, 10, 01), the carrier can be made unmodulated by forming a waveform that does not become L, and the carrier can be obtained by combining all data. The ON time can be made longer than a certain time. When the data (00) is continuous, the second and subsequent data use a waveform that is L. As a result, consistency between the clock and the data can be obtained, and erroneous recognition of the data can be prevented. Note that the modulation waveform of # 1logic "00" is used only for the first 00 data of the continuous 00 data. However, the second 00 data of the continuous 00 data is used as long as the data is not erroneously recognized. It is also possible to increase the number of modulation waveforms of # 1logic "00" like 00 up to 00 or 00 up to the third time. Further, when the data of 00 is continuous, the modulation waveform of # 1logic “00” and the modulation waveform of # 2logic “00” can be used alternately. Thereby, power can be stably supplied to the RFID tag 10.
[0050]
Other embodiments.
The above-described embodiment shows a preferred embodiment, and the scope of the present invention is not limited to the following embodiment. For example, the H time and L time of the waveform corresponding to each data, the modulation waveform, the unit modulation section, the carrier signal, the clock frequency, and the modulation method are merely examples, and the present invention is not limited thereto. The modulation waveform is not limited to the waveform generated for every two bits, but may be generated for any n bits (n is an integer of 1 or more). Furthermore, in the above-described embodiment, two types of waveforms are prepared for only the data of 00. However, the present invention is not limited to this, and two types of waveforms are provided for 01, 11, and 11 (corresponding values in the case of n bits). May be prepared. Of course, it is desirable to prepare two types of modulation waveforms at values corresponding to the modulation waveforms whose L timing is the earliest. It is desirable that the other modulation waveform be an unmodulated waveform. Thus, the carrier OFF time when data is switched can be further shortened without erroneously recognizing data, and power supply can be stabilized.
[0051]
Furthermore, an unmodulated waveform may be used only immediately after a specific value. For example, the same effect can be obtained by setting the non-modulated waveform only immediately after the data (11 in the first embodiment) corresponding to the modulation waveform having the latest L timing. In this case, the timing at which the flag is set to 0 in the flow shown in FIG. The modulation waveforms to be prepared are not limited to two types, but three or more types may be prepared, and the modulation waveform may be selected from the three types.
[0052]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the communication system and communication system of the non-contact system which can supply power stably, and the external device or RFID tag used for the said communication system can be provided.
[Brief description of the drawings]
FIG. 1 is a configuration diagram illustrating a communication system according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a waveform for modulating data in the communication system according to the first exemplary embodiment of the present invention.
FIG. 3 is a diagram showing signals transmitted in the communication system according to the first exemplary embodiment of the present invention.
FIG. 4 is a flowchart showing a flow of generating a modulation waveform in the communication system according to the first exemplary embodiment of the present invention;
FIG. 5 is a diagram showing a waveform for modulating data in a conventional communication system.
FIG. 6 is a diagram showing signals transmitted in a conventional communication system.
[Explanation of symbols]
10 RFID tag, 11 antenna coil, 12 power generation unit,
13 memory, 14 control circuit, 20 reader / writer
21 controller, 22 transceiver / receiver, 23 antenna coil
30 hosts

Claims (17)

A communication method in which data communication is performed in a contactless manner by a tag having an antenna and an external device that transmits data to the tag,
Generating a modulation waveform corresponding to the value of the n-bit data for every n-bit (n is an integer of 1 or more) data of the transmission data;
Generating a carrier signal;
Modulating a carrier signal based on the modulation waveform to generate a transmission signal;
Transmitting the transmission signal to the tag;
The tag generates a power source based on the transmission signal,
In the step of generating the modulation waveform, it is determined whether the n-bit data is a first value. If the n-bit data is the first value, a first modulation waveform or a second modulation waveform is generated. Communication method used. The communication method according to claim 1, wherein a second modulation waveform is generated at a first value immediately after the value other than the first value. 3. The communication method according to claim 1, wherein the modulation waveform has two levels, an L level and an H level, and changes to the L level at different timings depending on the value of the n-bit data. The communication system according to claim 3, wherein in the transmission signal, no carrier is transmitted while the modulation waveform corresponds to the L level. 5. The communication method according to claim 3, wherein the first modulation waveform is a waveform having the earliest timing of L level as compared with a modulation waveform corresponding to a value other than the first value. 6. . The communication method according to claim 5, wherein the second modulation waveform is a waveform that does not become L level. The communication method according to claim 1, wherein the communication method is modulated by an ASK method. A communication system comprising a tag having an antenna and an external device that transmits data to the tag by a non-contact method,
A power generation unit configured to generate power based on a signal transmitted from the external device,
A storage unit that stores information based on the data, by a power supply generated by the power generation unit,
A modulating waveform generating unit configured to generate the modulating waveform that becomes the L level at different timings depending on the value of the n-bit data for each n-bit data (n is an integer of 1 or more); ,
A transmission signal generation unit that generates a transmission signal based on the modulation waveform,
A transmitting unit that transmits the transmission signal to the tag,
A communication system in which two or more different types of modulation waveforms having a first modulation waveform and a second modulation waveform are associated with a first value of the n-bit data values. The communication system according to claim 7, wherein the tag is an RFID tag. The first modulation waveform is a waveform having the earliest timing of the L level as compared with a modulation waveform corresponding to a value other than the first value,
9. The communication method according to claim 7, wherein the second modulation waveform is used for a first value immediately after a value other than the first value in the transmission data. The communication method according to claim 9, wherein the second modulation waveform is a waveform that does not become L level. An external device that has an antenna for receiving a signal and transmits data to an RFID tag that generates power based on a signal received by the antenna,
A modulation waveform generating unit that generates a modulation waveform corresponding to the value of the n-bit data for each n-bit (n is an integer of 1 or more) transmission data;
A transmission signal generation unit that generates a transmission signal based on the modulation waveform,
A transmission unit for transmitting the transmission signal,
An external device in which the modulation waveform generation unit generates a first modulation waveform or a second modulation waveform when the value of the n-bit data is a first value. The first modulation waveform is a waveform having the earliest timing of the L level as compared with a modulation waveform corresponding to a value other than the first value,
The external device according to claim 11, wherein the second modulation waveform is used for a first value immediately after a value other than the first value in the transmission data. An RFID tag for receiving, in a non-contact manner, a signal in which one frame of data is modulated by a modulation waveform corresponding to the value of the n-bit data for every n-bit data (n is an integer of 1 or more). ,
A receiving unit that receives the signal,
A power generation unit that generates power based on the received signal;
Power is supplied by the power generation unit, a storage unit that stores data based on the received signal,
A demodulation unit that demodulates the signal and detects the modulation waveform,
A control unit that is driven by a power supply generated by the power generation unit and records data based on the modulation waveform in the storage unit, wherein the control unit has two different modulation waveforms having the same value. An RFID tag that recognizes 14. The RFID tag according to claim 13, wherein one of the two different modulation waveforms has the earliest timing when the L level is at the L level. The RFID tag according to claim 14, wherein the other of the two different modulation waveforms is a waveform that does not become L level. When the modulation waveform corresponds to the L level, the carrier of the signal is turned off,
16. The RFID tag according to claim 14, wherein the demodulation unit detects a modulation waveform based on a time when the carrier of the signal is turned off.

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