KR101448997B1 - Radio Frequency IDentification reader - Google Patents

Abstract

The RFID interrogator according to the embodiment generates an energy signal by combining some of the frequency signals of the tag signal interval with the first frequency signal among the linking timing standards defined in the RFID protocol, 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 interfering with the reader and without interfering with the signal between the reader and the tag, and it is possible to supply the tag with a sufficient energy. In addition, there is an effect that it is possible to construct an RFID system capable of preventing a decrease in reception sensitivity and an increase in SNR (Signal to Noise Ratio) and minimizing the influence of a DC offset according to a DC level.

RFID reader, tag, DC offset, SNR, UHF band, ISM band

Description

An RFID reader {Radio Frequency IDentification reader}

The embodiment discloses an RFID reader.

Ubiquitous network technology has attracted the attention of many people. Ubiquitous network technology means a technology that makes it possible to connect to various networks smoothly regardless of time and place.

Such a ubiquitous network can be implemented as a short-range wireless communication system, for example, an RFID system. The RFID system is composed of a reader attached to an article, and a reader reading information of a tag and a tag using product information.

In the case of an RFID reader, since the tag is moved at a high speed, the propagation environment changes greatly, and the received signal changes largely according to the change of the external environment.

In particular, since a tag receives energy from a signal received from a reader, and the signal carrying the data and the signal used for the tag energy are transmitted through the same frequency band, the energy supply is not smooth and the reception sensitivity is lowered 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) have.

This may cause interference between the tag signal and the reader signal more seriously in the presence of a plurality of tags, which is an obstacle in improving the tag recognition rate.

Embodiments provide an RFID reader capable of facilitating the supply of tag energy and improving the tag recognition rate by separating a signal used as tag energy among signals transmitted between a reader and a tag.

The RFID interrogator according to the embodiment generates an energy signal by combining some of the frequency signals of the tag signal interval with the first frequency signal among the linking timing standards defined in the RFID protocol, The signal is generated as a data signal by combining with the second frequency signal.

According to the embodiment, the following effects can be obtained.

First, communication can be performed without interference between the interrogator and the interrogator between the interrogator and the tag, and it is possible to supply the energy with sufficient energy by the tag.

Second, there is an effect that an RFID system can be constructed which can prevent deterioration of reception sensitivity and increase in SNR (Signal to Noise Ratio) and minimize influence of DC offset according to DC level.

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

1 is a block diagram schematically illustrating 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, a second mixer 192, A first oscillation circuit 204, a second oscillation 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 balun circuit 130, a third mixer 146, a fourth mixer 142, a third oscillation circuit 144 A first LPF 152, a second LPF 154, and a demodulating unit 155. The first LPF 154 and the demodulating unit 155 are connected to each other.

The control unit 160 generates a control signal to control the demodulation unit 155, the first synchronous circuit 206 and the second synchronous circuit 200. The control unit 160 controls the demodulation unit 155, the first synchronous circuit 206 and the second synchronous circuit 200 according to the PIE (Pulse-Interval Encoding) And sends control signals for phase adjustment and selection timing.

The PIE format may be a format conforming to the UHF RFID Protocol such as ISO 18000-A, ISO 18000-B, EPC (Generation-0), EPC Generation-1 or EPC Generation-2. It is assumed that the embodiment uses the EPC Generation-2 protocol.

As such modulation standard is applied, the RFID interrogator 100 according to the embodiment can be implemented as a DSB-ASK (Double Side Band-Amplitude Shift Keying), SSB-ASK (Single Side Band-Amplitude Shift Keying), a PR- Keying) can be used.

The controller 160 controls the RFID communication with the tag including the signal processor 162 and the signal separator 164. The signal processor 162 controls the reader and tag defined in the EPC Generation-2 UHF RFID Protocol Lt; RTI ID = 0.0 > transmission / reception < / RTI >

The signal separator 164 separates the tag signal section and the leader signal section of the signal processed by the signal processing section 162 and outputs the frequency signals of the part of the frequency of the tag signal and the frequency of the leader signal section, (224) and the second summer (222).

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

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

The timing diagram corresponding to the leader signal in the timing diagram shown in Fig. 2 is shown on the upper side, and the timing diagram corresponding to the tag signal is shown on the lower side.

When the reader section and the tag section are divided into a whole section corresponding to the reader section and the tag section, the read section is in a ready state, an arbitration state, a reply state, an acknowledged state, .

In addition, the leader signal is divided into a section 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 a corresponding interval of the tag signal is divided into CW Wave) section exists.

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

Each data interval 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" .

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

The following timing states, commands, data, time intervals, and the like will be described in order.

First, the ready state means a state in which the tag can communicate without losing energy. When the tag energy is exhausted, the RFID tag can return to the ready state.

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

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

Fourth, the arbitration state is a state in which the tag and the reader proceed with the connection procedure in a state where the tag response is not performed.

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 the communication authority is transferred from the reader to the tag, and it can be determined whether or not a signal is received from the tag antenna. The first time interval T1 may exist in each state interval.

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

Eighth, the QueryRep command constituting the arbitration state is a command for decreasing the reader slot value and retransmitting the response request signal when there is no tag response (No reply).

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

And a second time interval T2 constituting the response state means a time for which the tag is secured for demodulating the leader signal.

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

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

In the thirteenth, the ACK command constituting the confirmation state means a confirmation code for the tag response.

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

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

Sixteenth, the Req_RN command configuring the open state is a command sent to the tag to deliver the new RN 16.

The seventeenth, the Handle command constituting the open state is a state for processing a new command / response structure after the Req_RN command, and the new command / response structure may include all the structures corresponding to the various states described above.

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

As described above, the signal separator 164 transmits a frequency signal of a part of the frequency of the tag signal and the frequency of the leader signal section to the first summer 224 and the second summer 222, Some of the frequency signals of the section are signals corresponding to the first time interval T1 to the fourth time interval T4.

The reader signal section includes a period 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 an I signal and a Q signal having a phase difference of 180 degrees and are summed into a single signal in the first summer 224, Mixer 196, as shown in FIG.

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

The signal of the leader signal period is an I signal and a Q signal having a phase difference of 180 degrees, which is summed into a single signal by the second summer 222 and transmitted to the second mixer 192.

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

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

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

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

The phase locked signal is used to keep the oscillation frequency signal stable and stable.

The first oscillation circuit 204 and the second oscillation circuit 202 generate a first frequency signal and a second frequency signal respectively according to a phase synchronization signal and output the first frequency signal and the second frequency signal to the first mixer 196 and the second mixer 192, .

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

The transmission filter 210 blocks noise components generated in the combining process, and the power amplifier 220 amplifies the transmission signal at a transmittable power level.

The signal received through the receiving antenna 105 is transmitted to the balloon circuit 130 via the low noise amplifier 122 and the receiving filter 124.

The low noise amplifier 122 amplifies the noise component to a size that can be converted into an intermediate frequency signal by suppressing the noise component as much as possible, and the reception filter 124 filters only the signal of the 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 the output ends thereof are connected to a third mixer 146 and a fourth mixer 142, respectively.

The third oscillator 144 generates a second frequency signal in the UHF band according to the phase synchronization signal of the second synchronous circuit 200. The third mixer 146 and the fourth mixer 142 generate I Mixes the signal and the Q signal with the second frequency signal and converts it into a baseband signal.

The I and Q signals converted into the base band signal are mixed with noise components through the first LPF 152 and the second LPF 154, respectively, during the mixing process.

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

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that various changes and modifications may be made without departing from the spirit and scope of the invention. For example, each component specifically shown in the embodiments of the present invention can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

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

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

Claims (8)

Among the linking timing specifications of the reader and tag defined in the RFID protocol, A part of the frequency signal of the tag signal section is combined with the first frequency signal to generate an energy signal and the frequency signal of the leader signal section is combined with the second frequency signal to generate a data signal, A signal processing unit for processing a signal according to the timing standard; And a signal separator for separating and transmitting a frequency signal of a part of the tag signal section and a frequency signal of the leader signal section among the processed signals. A first mixer for generating the energy signal using the separated part of the frequency signals; And a second mixer for generating the data signal using the frequency signal of the separated leader signal period. The method according to claim 1, The RFID protocol is "Electronic Product Code (EPC) Generation-2 UHF RFID Protocol & Wherein the first frequency signal is an ISM (Indutrial, Scientific and Medica) band signal. The method of claim 1, wherein the second frequency signal An RFID reader that is a signal in the UHF (Ultra High Frequency) band. 2. The method of claim 1, wherein some frequencies of the tag signal interval are The frequency of the first time interval < RTI ID = 0.0 > T1 < / RTI & The frequency of the second time interval T2 that the tag takes to demodulate the leader signal, The frequency of the third time interval T3 at which the reader waits after transferring the communication authority to the tag, And a frequency of a fourth time interval (T4) secured with a minimum time between reader commands. delete The method according to claim 1, 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 according to claim 1, And a synthesizer for synthesizing the energy signal and the data signal into a transmission signal. 2. The method of claim 1, wherein the frequency signal of the leader signal interval is A Select state in which a command for selecting a tag to be added to or deleted from a communication inventory is executed; A Query command for sending a response request signal to a tag selected as a communication target, an Arbirate state for executing a QueryRep command for retransmitting a response request signal when there is no tag response; An acknowledgment state in which the reader transmits an acknowledgment code for the response of the tag, and the tag information is transmitted; An 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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