KR20070047935A - Radio frequency identification reader - Google Patents

Abstract

RFID reader according to the present invention includes a receiving processing stage and a transmitting processing stage, a plurality of antennas; A first switching unit configured to switch the antennas to transmit and receive signals sequentially or in groups; A second switching unit for separating the transmission / reception signal by switching the sequentially switched antennas to the reception processing stage or the transmission processing stage; And an isolation circuit, connecting the second switching unit and the receiving processing terminal when the receiving signal path is selected in the second switching unit, and when the transmitting signal path is selected in the second switching unit, the second switching unit. And a third switching unit for connecting the isolation circuit.

According to the present invention, since the number of antennas can communicate with the electronic tag in a wider area and can improve the isolation between the transmitting end and the receiving end, the transmission and reception signals can be processed by one antenna, so that the arrangement of the antennas is easy and the transmission and reception is performed. It is possible to improve the error rate, stability, recognition distance, etc. of the data, and to minimize the size of the RFID reader product. In addition, since the reception sensitivity is improved by 3 to 4 dB or more and the spurious phenomenon can be suppressed from occurring at the receiving end, the probability of malfunction at the receiving end can be reduced.

Description

RFID reader {Radio Frequency IDentification reader}

1 is a view schematically showing the components and connection form of a conventional RFID system.

2 is a circuit diagram schematically showing the components of a conventional RFID transceiver with a circulator.

3 is a view schematically showing the components and the connection form of the RFID system to which the RFID reader according to an embodiment of the present invention.

Figure 4 is a block diagram schematically showing the components of the RFID reader according to an embodiment of the present invention.

5 is a block diagram schematically illustrating the components of an electronic tag for communicating with an RFID reader according to an embodiment of the present invention.

6 is a view illustrating a connection form of the first switching unit, the second switching unit and the third switching unit according to an embodiment of the present invention.

7 is an experimental graph measuring waveforms of signals processed by an RF transmitter and an RF receiver of an RFID reader according to an embodiment of the present invention in units of 200 μs.

8 is an experimental graph measuring waveforms of signals processed by an RF transmitter and an RF receiver of an RFID reader according to an embodiment of the present invention in units of 10 μs.

<Explanation of symbols for main parts of drawing>

210: RFID reader 212: RF processing stage

211a, 211b, 211c, and 211d: antenna 212a: first switching unit

212b: second switching part 212c: third switching part

212d: RF Transmission Processing Unit 212e: RF Transmission Processing Unit

213: baseband processing stage 214: Q-RSSI circuit

215: I-RSSI circuit 216: control circuit

220: electronic tag

The present invention relates to an RFID reader, and more particularly, to a switching structure of an RFID reader having a plurality of antennas and improving the isolation between a transmitter and a receiver.

Currently, ubiquitous network technology has attracted the attention of many people, ubiquitous network technology means a technology that allows to naturally connect to various networks regardless of time and place.

As the next generation technology of the ubiquitous network technology, RFID technology may be cited. Among them, RFID technology introduced in commerce is representative. The commercial RFID system is composed of an electronic tag attached to a product and embedded with detailed information, and an RFID reader that reads the information of the electronic tag using RF communication, and the electronic tag attached to the product is an area where the RFID reader is located. It passes through and transmits information using RF communication, thus providing a foundation for efficiently managing logistics / distribution such as distribution, assembly, price change, and sales of goods.

Meanwhile, a receiver of a conventional RFID reader is generally implemented through envelope detection using an amplitude shift keying (ASK) modulation scheme. According to the conventional design scheme, a data recognition rate is lowered because a bit error rate is lowered. There is this.

Therefore, the radio wave environment varies greatly depending on factors such as the position and speed at which the electronic tag passes through the antenna area of the RFID reader, and the packaging material (for example, pallet load) of the product with the electronic tag. According to the change, an error rate, stability, recognition distance, etc. of data received by the RFID reader may be different.

1 is a view schematically showing the components and connection form of the conventional RFID system 100, the RFID reader 110, 120 is two, each having two switches and four antennas, the antenna They are arranged on both sides with the moving region of the electronic tag attached product.

The antenna is divided into a transmission and reception band, the first antenna 111 and the second antenna 112 are operated as a transmission antenna of the first RFID reader 110, the third antenna 113 and the fourth antenna 114. Is operated as a reception antenna of the second RFID reader 120. In addition, the fifth antenna 121 and the sixth antenna 122 is operated as a transmission antenna of the second RFID reader 120, and the seventh antenna 123 and the eighth antenna 124 are the second RFID reader 120. It is operated as a receiving antenna of.

The first switch 115 (or the fourth switch 126) switches the transmission signal transmitted from the first Tx processing stage 117 (or the second Tx processing stage 128) to form the first antenna 111 and the first antenna. The second antenna 112 (or the fifth antenna 121 and the sixth antenna 122) transmits the transmission signal alternately, and the second switch 116 (or the third switch 125) A signal received from the third antenna 113 and the fourth antenna 114 (or the seventh antenna 123 and the eighth antenna 124) is switched to switch the first Rx processing stage 118 or the second Rx processing stage 127. To pass).

In this way, the antenna is divided into a transmission band and a reception band. Unlike other mobile communication systems, in the RFID method, a transmit / receive signal processed by a tag and a reader uses the same frequency band. This is because it has a structure that processes them separately.

Therefore, according to the conventional RFID system, since the transmission and reception signals are separated and processed, the structure is complicated, and there is a problem that the probability of malfunction occurs, and the size of the RFID reader increases. In addition, since the RFID readers 110 and 120 are separated into antennas for transmission and reception on one RFID reader 110 and 120 as well, a plurality of RFID readers 110 and 120 are also provided, as shown in FIG. Increase to dogs.

In this configuration, the signals processed in the plurality of Rx / Tx processing stages provided in the first RFID reader 110 and the second RFID reader 120 must be divided and processed again in the baseband stage (not shown), or Since the signal processed from the RFID reader of the server must be separated and processed again at the server side (not shown), there is a problem that the system implementation is complicated and the installation cost increases. In particular, even if the number of antennas is provided in a large number, there is a limit in the installation area of the antenna for processing the transmission signal and the reception signal, so that the recognition rate of the tag is not significantly improved in the radio wave environment.

Meanwhile, various methods have been proposed in the related art so as to transmit and receive a signal to one antenna. In general, a method including a circulator in front of the antenna is used.

2 is a circuit diagram schematically showing the components of a conventional RFID transceiver with a circulator.

Referring to FIG. 2, the conventional RFID reader includes an antenna 10, a circulator 20, a transmission processing stage 30, and a reception processing stage 40, and the antenna 10 transmits and receives as described above. It has a structure of receiving or transmitting a signal together.

The first port of the circulator 20 is connected to the antenna, the second port and the third port is connected to the transmission processing stage 30 and the receiving processing stage 40, respectively.

When the power is input from any port, the circulator 20 transmits power to only one of the left or right ports, and does not transmit power to the other ports, so that the circulator 20 transmits with directionality as if the signal rotates in one direction. Be sure to Accordingly, the circulator 20 transmits a signal received through the antenna 10 to the reception processing terminal 40 in the counterclockwise direction, and transmits a signal from the transmission processing terminal 30 to the antenna 10. .

When processing the transmission and reception signal using the circulator in this way, there is a disadvantage that the isolation (isolation) to the transmission and reception terminal is reduced, and thus the selectivity of the receiver is reduced.

That is, the reading distance of the electronic tag, the energy supply distance to the electronic tag, and the recognition rate vary considerably according to the transmission power of the RFID reader. In order to meet the minimum standard, the RFID reader (including a handheld reader and a fixed reader) is usually used. The transmission processing stage 30 usually transmits a signal of high power of 1 W (EIRP; 4 W in the case of Effective lsotropic radiated power). For reference, EIRP is called “isotropic radiated power,” which is a measure of the power of an antenna main beam relative to an isotropic radiator, expressed as the product of the power supplied to the antenna and the gain in a given direction for the isotropic antenna. do.

However, since the circulator 20 has low isolation for each terminal, 25 dBm of the 30 dBm (1W) transmit power transmitted from the transmission processing stage 30 is transmitted through the circulator 20 to the antenna 10. But the remaining 5dBm of power is not isolated from the circulator and is drawn to the receiving end. Therefore, when the transmission signal is received, the receiving processing stage 40 may change the reference voltage to generate a power saturation state. In this case, the signal may not be properly processed or the device may be damaged.

Therefore, the present invention controls the switching operation to transmit the transmission and reception signals in sequence at each position when a plurality of antennas for transmitting and receiving signals are provided, thereby communicating with the electronic tag in a wider area with a smaller number of antennas. It is possible to provide an RFID reader having improved isolation between the transmitting signal stage and the receiving signal stage so that the transmission signal is fed back to the receiving signal stage so as not to affect the receiving signal stage. For that purpose.

In order to achieve the above object, the RFID reader according to the present invention includes a receiving processing stage and a transmitting processing stage, a plurality of antennas; A first switching unit configured to switch the antennas to transmit and receive signals sequentially or in groups; A second switching unit for separating the transmission / reception signal by switching the sequentially switched antennas to the reception processing stage or the transmission processing stage; And an isolation circuit, connecting the second switching unit and the receiving processing terminal when the receiving signal path is selected in the second switching unit, and when the transmitting signal path is selected in the second switching unit, the second switching unit. And a third switching unit connecting the isolation circuit.

In addition, the RFID reader according to the present invention further includes a control unit for transmitting a control signal of a switching operation to the first switching unit.

In addition, the RFID reader according to the present invention further includes a control unit for transmitting a control signal of a switching operation to the third switching unit.

In addition, the control signal processed in the RFID reader according to the present invention includes one or more of period information and order information of the switching operation.

In addition, the antenna provided in the RFID reader according to the present invention is disposed to the left and right of the region in which the electronic tag is moved.

In addition, the antenna provided in the RFID reader according to the present invention is arranged with different radio wave transmission and reception angles on the region in which the electronic tag is moved.

In addition, at least one switching unit of the first switching unit, the second switching unit, and the third switching unit of the RFID reader according to the present invention is provided with a semiconductor switching device chip.

In addition, the second switching unit of the RFID reader according to the present invention is further provided with an isolator at the transmission end side connection end.

Hereinafter, an RFID reader according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. An RFID reader according to an embodiment of the present invention is used in a logistics system.

3 is a view schematically showing the components and the connection form of the RFID system 200 to which the RFID reader 210 is applied according to an embodiment of the present invention.

Referring to FIG. 3, the RFID system 200 according to the embodiment of the present invention includes an RFID reader 210 and an electronic tag 220 including a plurality of antennas 211a, 211b, 211c, and 211d. 220 is attached to the goods passing through the logistics inspection area, the antennas 211a, 211b, 211c, 211d are arranged to the left and right of the area (inspection area) to which the electronic tag 220 is moved.

In the embodiment of the present invention, four antennas 211a, 211b, 211c, and 211d are provided, and two antennas are arranged to the left and right of the moving area of the electronic tag 220. In this case, each antenna may be installed with different radio wave transmission and reception angles.

As described above, the RFID reader 210 according to the embodiment of the present invention is provided as one, unlike the prior art, it is possible to control a plurality of antennas for transmitting and receiving signals.

4 is a block diagram schematically showing the components of the RFID reader 210 according to an embodiment of the present invention.

Referring to FIG. 4, the RFID reader 210 according to the embodiment of the present invention includes four antennas 211a, 211b, 211c, and 211d, an RF processing stage 212, a baseband processing stage 213, and a control circuit 216. ), A Q-RSSI circuit 214 and an I-RSSI circuit 215. The RF processing stage 212 includes a first switching unit 212a, a second switching unit 212b, and a third switching unit. A unit 212c, an RF reception processing unit 212d and an RF transmission processing unit 212e are provided.

The first switching unit 212a of the RF processing stage performs a switching operation so that the four antennas 211a, 211b, 211c, and 211d may be sequentially connected to the second switching unit 212b. , 211b, 211c, and 211d) may be combined in various ways.

In this case, since the first switching unit 212a performs a switching operation several times or more than ten times per second, the antennas may have the effect of simultaneously monitoring the entire region in which the electronic tag 220 is moved.

In addition, when the second switching unit 212b is connected to any one of four antennas 211a, 211b, 211c, and 211d connected to the first switching unit 212a, the second switching unit 212b transmits a transmission signal to the RF transmission processing unit 212e. In this case, the transmission and reception signals are separated and transmitted by performing a switching operation according to the case where the signal is transmitted from the antenna side to the antenna side and the case where the received signal is transferred from the antenna side to the RF receiving processor 212d.

As such, the first switching unit 212a and the second switching unit 212b are interlocked so that the antennas 211a, 211b, 211c, and 211d simultaneously process the transmission / reception signals while simultaneously moving the moving region of the electronic tag 220. You can watch.

The first switching unit 212a and the second switching unit 212b may be implemented in various forms, for example, SP4T (Single-Pole Quadruple-Throw, 4: 1 MUX / DEMUX), SPDT (Single Pole Dual) It is preferable that the second switching unit 212b includes an isolator at a connection end with the RF transmission processing unit 212e.

In this case, the RF transmitter 212e transmits a signal having a high power of 1W (EIRP = 4W), and a part of the transmission signals (signal component of about 5 dBm out of about 30 dBm in total) may cause the second switching unit 212b to operate. It flows in (feedback) to the RF receiving processing unit 212d via the via.

Therefore, in the process of switching from the transmission mode to the reception mode, an unwanted wave component is introduced into the RF reception processing unit 212d, and the magnitude of the input power of the received signal is changed. When the magnitude of the input power is changed in this way, the reference voltage is shaken, and the RF receiving processor 212d is affected in restoring data transmitted from the electronic tag 220.

In order to suppress such a phenomenon, a third switching unit 212c is provided between the second switching unit 212b and the RF receiving processing unit 212d, and the third switching unit 212c includes the second switching unit 212b. In the transmission mode, the signal path is connected to the ground terminal, and in the reception mode, the signal path is connected to the RF reception processor 212d.

Preferably, the third switching unit 212c may be implemented as a switching device chip having a bypass switching circuit connected to an isolation terminal. When the third switching unit 212c is provided, a loss of a signal may occur when a transmission signal is transmitted. It can be suppressed and attenuation effect of 25dB or more can be seen.

The RF receiving processor 212d includes a low noise amplifier, a band pass filter, a matching circuit, and the like, and receives the received signal from the first switching unit 212a, the second switching unit 212b, and the third switching unit 212c. The noise component is suppressed and amplified, and the amplified signal is transmitted to the baseband processor 213.

The RF transmitter 212e adjusts and amplifies the power gain of the transmission signal transmitted from the baseband processor 213, filters the mixed signal in the process of processing the received signal, and transmits the mixed signal to the second switching unit 212b. do.

The baseband processing stage 213 is connected to the RF transmission processing unit 212e and the RF reception processing unit 212d, respectively, and is composed of two parts for processing a transmission signal and a reception signal (components of the baseband processing stage 213). (Not shown), an I / Q demodulator, a low pass filter (LPF), an intermediate frequency amplifier, a modulator, an A / D converter, and the like are provided to process the received signal. Q signal separation / low frequency signal generation, filtering, amplification / modulation and A / D conversion.

The baseband processing stage 213 may include a D / A converter, a low pass filter, a demodulator, an intermediate main gain amplifier, an intermediate frequency filter, and the like to process digital signals into intermediate frequency signals and RF signals. The signal is converted into a signal, and the gain of the power is adjusted and transmitted to the RF transmission processor 212e.

The digital signal transmitted from the baseband processing stage 213 is transferred to the control circuit 216, the I-RSSI circuit 215, and the Q-RSSI circuit 214.

The I-RSSI circuit 215 is a circuit for measuring the reception strength of an in-phase (I) signal. Usually, the I-RSSI circuit 215 detects and corrects that the signal strength increases and becomes irregular due to interference or mixed noise components. Means a circuit used for the purpose.

The Q-RSSI circuit 214 measures a reception strength of a quadrature (Q) signal and performs a function similar to that of the I-RSSI circuit 215.

The control circuit 216 is provided with a communication protocol to control wireless communication with the electronic tag 220, and periodically sends an information request signal to determine the position of the electronic tag 220.

In addition, the control circuit 216 analyzes the code of the tag identification information received from the electronic tag 220 and demodulated by the baseband processing stage 213, in which the data format is converted and filtering is performed to extract necessary information. Process.

Here, the control circuit 216 may be a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

The FPGA circuit refers to a gate array circuit (logical integrated circuit) that can be added to the programming if necessary to implement the function of the RFID reader 210 outside the production process of the chip, the gate array and PLD (Programmable Logic Devices) ) Is implemented.

These FPGA circuits have the advantages of being able to use multiple I / Os like a gate array, programmable at a time, and increasing the utility of the gate by 95%.

The DSP (Digital Signal Processing) circuit processes algebraic operations on digital data obtained by converting analog signals to analog / digital (A / D) conversion and performs signal processing such as filtering and spectral analysis.

The DSP circuit is basically for real-time digital processing of analog signals, which is a mathematical operation semiconductor that can quickly and digitally process digital signals, and a microprocessor performs these functions but specializes only in mathematical operations. Slower than a circuit As such, the DSP circuit is a dedicated processor that pursues high speed and compactness, and when the DSP circuit is used, the system can be upgraded by replacing only software.

5 is a block diagram schematically illustrating the components of the electronic tag 220 for communicating with the RFID reader 210 according to an embodiment of the present invention.

Referring to FIG. 5, the electronic tag 220 includes a tag antenna 221, a reception demodulator 222, a transmission modulator 224, a power supply unit 223, a control unit 225, and a memory 226. do.

The tag antenna 221 receives an information request signal through a wireless channel or transmits processed tag identification information. Usually, a dipole antenna is used.

The power supply unit 223 is a device for supplying power to the reception demodulation unit 222, the control unit 225 and the transmission modulator 224. The electronic tag 220 is classified into an active method and a passive method according to the driving method of the tag antenna 221 and the power supply unit 223. For example, the electronic tag 220 and the RFID reader 210 In the active mode, UHF signals with a frequency band of about 400 MHz to 960 MHz are used.

The reception demodulation unit 222 demodulates the incoming information request signal into digital data and transmits the received information request signal to the control unit 225. The control unit 225 analyzes a code of the demodulated information request signal to provide tag identification information. Create

In addition, the control unit 225 has a communication protocol to control wireless communication with the RFID reader 210. In this case, the memory 226 stores the information code system, and the control unit 225 generates the tag identification information using the same.

The transmission modulator 224 modulates the generated tag identification information into an RF signal, and the modulated tag identification information is transmitted to the RFID reader 210 through a tag antenna 221.

6 is a diagram illustrating a connection form of the first switching unit 212a, the second switching unit 212b and the third switching unit 212c according to an embodiment of the present invention.

Referring to FIG. 6, the first switching unit 212a has four signal paths connecting the four antennas 211a, 211b, 211c, and 211d and the second switching unit 212b. The control voltage terminals Vctl1 and Vctl2 to which the control signal (voltage) is applied, and the power supply terminal Vcc for supplying power to the switch are provided.

In addition, the first switching unit 212a includes a high frequency switching circuit that can be implemented in various forms as described above, and includes a decoder that interprets the control voltage and logically controls the switching operation.

The control circuit 216 has a program in which cycle information, order information, etc. of the switching operation is reflected, and executes the program to send a control signal to the control voltage terminal of the first switching unit 212a.

The second switching unit 212b has two signal paths that connect the first switching unit 212a to the RF transmission processing unit 212e and the third switching unit 212c, and the third switching unit 212c is The second switching unit 212b is connected to the RF receiving processor 212d, and another transmission path has a structure connected to the ground terminal.

The second switching unit 212b and the third switching unit 212c have control voltage terminals Vctl3 and Vctl4, a power supply terminal Vcc, a high frequency switching circuit, a decoder, and the like, like the first switching unit 212a. do.

A saw filter (SAW) for filtering noise components that may occur in a switching operation between the second switching unit 212b and the RF transmission processing unit 212e and between the second switching unit 212b and the third switching unit ( 10 and 12 are provided, and the isolator 14 is connected to the RF transmission processing unit 212e side as described above.

The control circuit 216 grasps input paths of the transmission signal and the reception signal, generates a control signal, and transfers the generated control signal to the second switching unit 212b or the third switching unit 212c.

7 is an experimental graph in which waveforms of signals processed by the RF transmitter 212e and the RF receiver 212d of the RFID reader 210 are measured in units of 200 μs, and FIG. 8 is an embodiment of the present invention. An experimental graph in which waveforms of signals processed by the RF transmitter 212e and the RF receiver 212d of the RFID reader 210 are measured in units of 10 μs, wherein the x coordinate of each graph represents a time axis. , y-coordinate means voltage axis.

"Channel 1 (C1)" in FIG. 7 is a waveform when a reference voltage of 5 V is provided, and "Channel 2 (C2)" is a waveform when a reference voltage of 500 mV is provided, for example, a time interval of 432 μs is 160 mV. Corresponds to the voltage interval.

In addition, "channel 1 (C3)" in Figure 8 is a waveform when a reference voltage of 5V is provided, "channel 2 (C4)" is a waveform when a reference voltage of 500mV is provided, for example, a time interval of 128μs Corresponds to a voltage interval of 120 mV.

"D1" in FIG. 7 and "D3" in FIG. 8 are regions in which the waveform of the transmission signal is shown, and "D2" in FIG. 7 and "D4" in FIG. 8 are regions in which the waveform of the received signal is shown. When comparing the two regions in FIG. 8, it can be seen that the reception signal is processed with little change in the reference voltage of the reception signal when switching from the transmission mode to the reception mode.

That is, it can be seen that the isolation characteristics between the RF transmission processing unit 212e and the RF reception processing unit 212d are improved by the third switching unit 212c of the RFID reader 210 according to the embodiment of the present invention.

The present invention has been described above with reference to the preferred embodiments, which are merely examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above. 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.

According to the RFID reader according to the present invention, since the antenna can communicate with the electronic tag in a wider area with a small number of antennas and can improve the isolation between the transmitting end and the receiving end, the transmission and reception signals can be processed by one antenna. It is easy to improve the error rate (stability), stability (stability), recognition distance, etc. of the transmission and reception data according to the change of the radio wave environment, and can minimize the size of the RFID reader products.

In addition, since the power of the transmitting end is effectively blocked, the receiving sensitivity is improved by 3 to 4 dB or more and the spurious phenomenon can be suppressed from occurring at the receiving end, thereby reducing the probability of malfunction at the receiving end.

Claims (8)

An RFID reader comprising a receiving end and a transmitting end, A plurality of antennas; A first switching unit configured to switch the antennas to transmit and receive signals sequentially or in groups; A second switching unit for separating the transmission / reception signal by switching the sequentially switched antennas to the reception processing stage or the transmission processing stage; And And an isolation circuit, connecting the second switching unit and the receiving processing stage when the receiving signal path is selected in the second switching unit, and connecting the second switching unit and the receiving processing terminal when the transmitting signal path is selected in the second switching unit. And a third switching unit for connecting the isolation circuit. The method of claim 1, RFID reader, characterized in that further provided with a control unit for transmitting a control signal of the switching operation to the first switching unit. The method of claim 1, And a control unit for transmitting a control signal of a switching operation to the third switching unit. The method of claim 2, wherein the control signal is RFID reader, characterized in that it comprises one or more of period information, order information of the switching operation. The method of claim 1, wherein the antenna RFID reader, characterized in that arranged in the left and right of the area to which the electronic tag is moved. The method of claim 1, wherein the antenna RFID reader, characterized in that arranged on the area where the electronic tag is moved with different radio transmission and reception angles. The RFID reader according to claim 1, wherein at least one switching unit of the first switching unit, the second switching unit, and the third switching unit is provided with a semiconductor switching device chip. The method of claim 1, wherein the second switching unit RFID reader, characterized in that the isolator is further provided at the transmitting end connection end.

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