KR20090017234A - ＲＦＩＤ Reader - Google Patents

Abstract

According to an embodiment of the present invention, an RFID reader generates an energy signal by synthesizing a part of frequency signals of a tag signal interval with a first frequency signal among linking timing standards of a reader and a tag defined in an RFID protocol and generating a frequency of the reader signal interval The signal is generated as a data signal by combining with the second frequency signal.

According to the embodiment, it is possible to perform communication without inter-reader interference and signal interference between the reader and the tag, and there is an effect of providing a smooth energy supply to the tag. In addition, there is an effect that it is possible to build an RFID system that can reduce the reception sensitivity, increase the signal to noise ratio (SNR), and minimize the effect of the DC offset according to the DC level.

Description

RFID reader {Radio Frequency IDentification reader}

An embodiment discloses an RFID reader.

Ubiquitous network technology has attracted a lot of attention, and ubiquitous network technology refers to a technology that allows a user to naturally connect to various networks regardless of time and place.

Such a ubiquitous network may be implemented as a short range wireless communication system, for example, an RFID system. The RFID system includes a tag attached to an article and embedded with article information, and a reader for reading the tag information using RF communication.

In the case of the RFID reader, the radio wave environment is severely changed due to the tag moving at high speed, and the received signal is greatly changed according to the change of the external environment.

In particular, the tag is supplied with energy using a signal received from the reader, and since the signal containing the data and the signal used as the tag energy are transmitted through the same frequency band, the supply of energy is not smooth and the reception sensitivity is deteriorated. have.

In addition, the supply of the energy signal and the data signal through the same frequency band affects the interpretation of the data signal and causes a DC offset phenomenon, which lowers the signal to noise ratio (SNR) and shortens the life of the reader equipment. have.

This may cause more serious interference between the tag signal and the reader signal when there are a plurality of tags, and is an obstacle to improving the tag recognition rate.

The embodiment provides an RFID reader capable of smoothly supplying tag energy and improving tag recognition rate by separating a signal used as tag energy among signals transmitted between the reader and the tag.

According to an embodiment of the present invention, an RFID reader generates an energy signal by synthesizing a part of frequency signals of a tag signal interval with a first frequency signal among linking timing standards of a reader and a tag defined in an RFID protocol and generating a frequency of the reader signal interval The signal is generated as a data signal by combining with the second frequency signal.

According to the embodiment, the following effects are obtained.

First, communication can be performed without inter-reader interference and signal interference between the reader and the tag, and there is an effect of providing a smooth energy supply with the tag.

Second, there is an effect to build an RFID system that can prevent a decrease in reception sensitivity, increase the signal to noise ratio (SNR), and minimize the effect of the DC offset according to the DC level.

An RFID reader according to an embodiment will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically illustrating the components of an RFID reader according to an embodiment.

Referring to FIG. 1, the RFID reader 100 according to the embodiment includes a controller 160, a first summer 224, a second summer 222, a first mixer 196, and a second mixer 192. , A first oscillator circuit 204, a second oscillator circuit 202, a synthesizer 198, a transmission filter 210, a power amplifier (PA) 220, a transmission antenna 110, a reception antenna 105 ), A low noise amplifier (LNA) 122, a reception filter 124, a balloon circuit 130, a third mixer 146, a fourth mixer 142, and a third oscillation circuit 144. ), A first LPF (Low Pass Filter) 152, a second LPF 154, and a demodulator 155.

The control unit 160 generates a control signal to control the demodulation unit 155, the first synchronization circuit 206, and the second synchronization circuit 200. In this case, the control unit 160 controls the demodulation unit 155 according to a pulse-interval encoding (PIE) format. The control signal for phase adjustment and selection timing is sent.

The PIE format may be applied according to UHF RFID Protocol such as ISO 18000-A, ISO 18000-B, Electronic Product Code (EPC) Generation-0, EPC Generation-1, and EPC Generation-2. The example assumes that the EPC Generation-2 protocol is used.

As the modulation standard is applied, the RFID reader 100 according to the embodiment includes a double sideband-amplitude shift keying (DSB-ASK), a single sideband-amplitude shift keying (SSB-ASK), and a phase reversal-amplitude shift (PR-ASK). All of the modulation and demodulation methods such as keying) can be used.

The controller 160 includes a signal processor 162 and a signal separator 164 to control RFID communication with the tag. The signal processor 162 includes a reader and a tag defined in the EPC Generation-2 UHF RFID Protocol. Transmit and receive signals are processed according to the linking timing standard.

In addition, the signal separator 164 separates the tag signal section and the reader signal section among the signals processed by the signal processor 162, and first sums some frequency signals of the tag signal section and the frequency signals of the reader signal section, respectively. Transfer to group 224 and second summer 222.

Hereinafter, the connection timing standard will be described with reference to FIG. 2.

2 is a diagram illustrating a timing standard of the EPC Gen-2 standard used in the RFID reader 100 according to the embodiment.

Among the timing diagrams shown in FIG. 2, the timing diagram corresponding to the reader signal is shown at the upper side, and the timing diagram corresponding to the tag signal is shown at the lower side.

When the reader signal and the tag signal are divided into corresponding sections, the ready state, the arbitration state, the reply state, the acknowledge state, the open state, etc. Can be distinguished.

In addition, the reader signal is divided into sections in which a select command, a QueryRep command, a QueryRep command, an ACK command, and a Req_RN command are processed according to a command type, and each section is CW (Continuous) corresponding to a tag signal. Wave) section exists.

The tag signal is processed in the CW period, RN16 (16-bit random or pseudo-random number), PC (Protocol Control) bits, EPC (Electronic Product Code) bits, CRC16 (Cyclic Redundancy Check) bits, application data (Handle data) ), And the like.

Each data section of the tag signal is divided into four types of time intervals.

Hereinafter, the four time intervals are referred to as "first time interval T1", "second time interval T2", "third time interval T3", and "fourth time interval T4". Shall be.

The reader 100 according to an embodiment processes the reader signal as a transmission signal and processes the tag signal as a reception signal.

Such timing states, commands, data, time intervals, etc. will be described in order.

First, the ready state refers to a state in which a tag can communicate without losing energy. When the tag energy is exhausted, the ready state may be returned to the ready state.

Second, a select command for configuring the ready state is a command for selecting a tag to be added or deleted from the inventory.

Third, the fourth time interval T4 constituting the ready state means a minimum interval secured between reader commands.

Fourth, the Arbitrate state is a state in which a tag and a reader perform a connection process together in a state where a tag response is not made.

Fifth, a query command constituting the arbitration state is a command for sending a response request signal to a tag selected as a communication target.

Sixth, the first time interval T1 constituting the arbitration state means a time at which communication authority is transferred from a reader to a tag, which may be determined whether a signal is received from a tag antenna. The first time interval T1 may exist in each state section.

Seventh, the third time interval T3 constituting the arbitration state means the waiting time of the leader for the response request signal.

Eighth, the QueryRep command constituting the arbitration state is a command for reducing the reader slot value and resending the response request signal when there is no tag response.

Ninth, the reply state is a state in which a tag transmits a response code to a reader.

Tenth, the second time interval T2 constituting the response state means the time that the tag is secured to demodulate the reader signal.

Eleventh, RN16 (16-bit random or pseudo-random number) constituting the response state means a response code of a tag.

Twelfth, the acknowledgment state is a state in which a reader transmits a response code of a tag and tag information is transmitted.

Thirteenth, the ACK command configuring the acknowledgment state means an acknowledgment code for a tag response.

Fourteenth, the PC (Protocol Control) bits are information on a physical layer of tag information, and the EPC (Electronic Product Code) bits are tag device information for identification. In addition, the CRC16 (Cyclic Redundancy Check) is error detection information.

Fifteenth, the open state is a state in which a series of commands and responses for tag information transfer are processed after tag recognition.

Sixteenth, the Req_RN command constituting the open state is a command sent to the tag to deliver a new RN16.

Seventeenth, the Handle command configuring the open state is a state of processing a new command / response structure after the Req_RN command, and the new command / response structure may include all of the structures corresponding to the various states described above.

In addition, the timing specification according to the EPC protocol may include more various time intervals.

As described above, the signal separator 164 transfers a part of the frequency signal of the tag signal period and the frequency signal of the reader signal period to the first summer 224 and the second summer 222, respectively, the tag signal. Some of the frequency signals in the section mean signals corresponding to the first time interval T1 to the fourth time interval T4.

The reader signal section may include a section in which a select command, a QueryRep command, a QueryRep command, an ACK command, and a Req_RN command are processed.

The signals corresponding to the first time interval T1 to the fourth time interval T4 are I and Q signal states having a phase difference of 180 degrees, which are summed into a single signal by the first summer 224 to form a first signal. Delivered to mixer 196.

The first mixer 196 generates an energy signal by using the first frequency signal supplied from the first oscillator 204 as a carrier signal and synthesizing it with the signal transmitted from the first summer 224.

In addition, the signals of the reader signal section are I and Q signal states having a phase difference of 180 degrees, which are summed into a single signal by the second summer 222 and transferred to the second mixer 192.

The second mixer 192 generates a data signal by using the second frequency signal supplied from the second oscillator 202 as a carrier signal and combining the signal with the signal transmitted from the second summer 222.

Here, the first frequency signal is a signal of the ISM (Indutrial, Scientific and Medica) band, the second frequency signal is a signal of the Ultra High Frequency (UHF) band.

Therefore, since the energy signal and the data signal have different frequency bands and are synchronized in different sections according to the timing standard, interference, data interpretation error, DC offset, and redundant modulation and demodulation can be eliminated.

The first synchronization circuit 206 adjusts the phase synchronization signal corresponding to the first frequency signal according to the control signal of the controller, and the second synchronization circuit 200 adjusts the phase synchronization signal corresponding to the second frequency signal. do.

The phase synchronization signal is used to keep the oscillation frequency signal stable without flowing.

The first oscillator 204 and the second oscillator 202 generate a first frequency signal and a second frequency signal according to the phase synchronization signal, respectively, and the first mixer 196 and the second mixer 192, respectively. To pass.

The synthesizer 198 synthesizes an energy signal and a data signal into one signal form according to the timing standard, and the synthesized signal is transmitted through a transmission filter 210, a power amplifier 220, and a transmission antenna 110. .

The transmission filter 210 blocks the noise component generated during the synthesis process, and the power amplifier 220 amplifies the transmission signal to a transmittable power level.

Meanwhile, the signal received through the reception antenna 105 is transmitted to the balloon circuit 130 through the low noise amplifier 122 and the reception filter 124.

The low noise amplifier 122 suppresses noise components as much as possible and amplifies them to a magnitude convertible to an intermediate frequency signal, and the reception filter 124 filters only signals of a corresponding band.

The balloon circuit 130 separates the filtered signal into an I signal and a Q signal having a phase difference of 180 degrees, and an output terminal is connected to the third mixer 146 and the fourth mixer 142, respectively.

The third oscillator circuit 144 generates a second frequency signal in the UHF band according to the phase synchronization signal of the second synchronization circuit 200, and the third mixer 146 and the fourth mixer 142 are each I; The signal and the Q signal are mixed with the second frequency signal and converted into a baseband signal.

The I and Q signals, which are converted into baseband signals, are respectively passed through a first low pass filter (LPF) 152 and a second LPF 154 to remove mixed noise components during the mixing process.

The demodulator 155 includes an analog to digital converter (ADC), demodulates a baseband signal into a digital signal, and transmits the demodulated signal to the controller 160.

The present invention has been described above with reference to preferred embodiments thereof, which are merely examples and are not intended to limit the present invention, and those skilled in the art do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications which are not illustrated above in the scope are possible. For example, each component specifically shown in the embodiment of the present invention can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 is a block diagram schematically showing the components of an RFID reader according to an embodiment;

2 is a diagram illustrating a timing standard among Electronic Product Code (EPC) standards used in an RFID reader according to an embodiment.

Claims (8)

Among the linking timing standards of readers and tags defined in the RFID protocol, The RFID reader generates some energy signals by synthesizing the frequency signals of the tag signal section with the first frequency signal and generates the data signals by synthesizing the frequency signals of the reader signal section with the second frequency signal. The method of claim 1, The RFID protocol is "Electronic Product Code (EPC) Generation-2 UHF RFID Protocol", The first frequency signal is an RFID reader of the ISM (Indutrial, Scientific and Medica) band. The method of claim 1, wherein the second frequency signal is RFID reader, a signal in the Ultra High Frequency (UHF) band. The method of claim 1, wherein the some frequency of the tag signal interval is Frequency of the first time interval T1 at which the communication authority is transferred from the reader to the tag, The frequency of the second time interval T2 it takes for the tag to demodulate the reader signal, The frequency of the third time interval (T3) that the reader waits after transferring the communication authority to the tag, RFID reader comprising at least one of the frequencies of the fourth time interval (T4) secured to the minimum time between reader commands. The method of claim 1, A signal processor which processes a signal according to the timing standard; And a control unit including a signal separation unit configured to separate and transmit a part of a frequency signal of the tag signal period and a frequency signal of the reader signal period among the processed signals. A first mixer configured to generate the energy signal using the separated partial frequency signal; And a second mixer configured to generate the data signal using the frequency signal of the separated reader signal section. The method of claim 5, A first oscillator circuit for providing the first frequency signal to the first mixer; And And a second oscillator circuit for providing the second frequency signal to the second mixer. The method of claim 1, And a synthesizer for synthesizing the energy signal and the data signal into a transmission signal. The method of claim 1, wherein the frequency signal of the reader signal interval is A select state in which a command for selecting a tag to be added or deleted in the inventory is executed; An Arbirate state in which a Query command for sending a response request signal to a tag selected as a communication target and a QueryRep command for retransmitting a response request signal when there is no tag response are executed; An acknowledgment state in which the reader transmits an acknowledgment code for the response of the tag and the tag information is transmitted; RFID reader including data corresponding to one or more states of a handle state in which information is exchanged after retransmission of a tag response code.

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