KR101210042B1 - Radio Frequency IDentification tramceiver system - Google Patents

Abstract

RFID transmitting and receiving system according to the present invention comprises a mixer unit for converting a signal received through the antenna terminal to an intermediate frequency signal; A signal limiter connected to the front end of the mixer to limit an interference signal by cutting out an area other than a carrier frequency of a received signal; And a controller which processes the transmitted / received signal into a digital signal and transmits a control signal to the signal limiter to provide a limiting reference for the interference signal.

According to the present invention, since the tag signal can be stably restored / processed by eliminating the interference between the tag signal and the noise component signal, communication can be performed without interference between readers, and the manufacturing cost of the RFID transmission / reception system can be reduced. Therefore, the size of the product can be minimized. In addition, since the voltage of the transmission signal can be tuned on the same circuit according to the chip type of the controller, there is no need to change the circuit or add a separate component.

Description

RFID transmission / reception system {Radio Frequency IDentification tramceiver system}

1 is a view showing an example of a transmission and reception separation unit of a typical RFID transmission and reception system.

Figure 2 is a block diagram schematically showing the components of the RFID transmission and reception system according to an embodiment of the present invention.

3 is a diagram illustrating an embodiment in which the Rx interference signal blocking unit and the Tx interference signal blocking unit are implemented as diodes in an RFID transceiver system according to an exemplary embodiment of the present invention.

Figure 4 is a schematic diagram showing the components of the signal limiting unit of the RFID transmission and reception system according to an embodiment of the present invention.

5 is a graph measuring transmission and reception signals of the RFID transmission and reception system according to an embodiment of the present invention.

6 is a graph measuring a carrier frequency carrying a transmission and reception signal of the RFID transmission and reception system according to an embodiment of the present invention.

7 is a graph showing a reference voltage value set by the voltage adjusting unit of the RFID transceiver system according to an embodiment of the present invention to adjust the voltage of the digital signal.

Description of the Related Art

100: RFID transceiver system 105: antenna

110: Rx interference signal blocking unit 120: signal limiting unit

125: LNA 130: balloon circuit

135: first mixer 140: second mixer

145: first phase synchronization circuit unit 150: demodulation unit

155: controller 160: modulator

165: second phase synchronizing circuit section 175: voltage adjusting section

180: PAM 185: Tx interference signal blocking unit

The present invention relates to an RFID transmission and reception system.

Nowadays, ubiquitous network technology is attracting 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.

An example of such ubiquitous network technology is RFID technology, and among them, RFID technology introduced in commerce is representative.

In general, an RFID system includes an electronic tag attached to an article and embedded with detailed information, and an RFID reader that reads the information of the electronic tag using RF communication. Unlike a mobile communication terminal, an RFID system transmits and receives an RFID tag. It transmits and receives signals without separating the frequency band, and has a structure that separates and processes the transmitted and received signals at the base end.

Therefore, in the RFID transmission / reception system, transmission / reception antennas may be separated in order to distinguish a transmission path and a reception path. In this case, signal interference occurs between a plurality of antennas, so that a signal received from an electronic tag has a lower recognition rate and a larger system size. There is a problem.

For this reason, the RFID transmission and reception system is designed to process a transmission and reception signal by sharing one antenna. When one antenna is used, a signal of a tag moving at a high speed becomes more sensitive to changes in the radio wave environment, and particularly a frequency between RFID readers. The interference phenomenon greatly affects the recognition rate of the RFID tag.

For example, when a large number of tags exist in an area where a plurality of RFID readers are installed, tag signals using the same frequency band may be simultaneously received by the RFID readers. In this case, interference between tag signals may occur and the RFID reader may There is a problem that the signal cannot be processed and the data recognition rate is further lowered.

In addition, when the transmission signal of another RFID reader or its own transmission signal is transmitted to the receiving end of the RFID reader, the transmission signal may act as an interference signal, which may make processing of the tag (reception) signal more difficult.

In order to prevent the transmission signal from acting as an interference signal of the reception signal, a transmission and reception separation unit is generally located in front of the antenna.

1 is a view showing an example of the transmission and reception separation unit 12, 22 of the general RFID transmission and reception system (10, 20), Figure 1 (a) is a case where the transmission and reception separation unit implemented as a circulator 12 1 (b) shows a case where the transmission / reception splitter is implemented as a branch line combiner 22.

The circulator 12 has three ports. When power is input from one port, the circulator 12 transmits power to only one of the left or right ports and does not transmit power to the other ports. As a circuit which transmits directionally as it rotates, a transmission signal is transmitted from the transmission path end 13 to the antenna 11 and a reception signal is transmitted from the antenna 11 to the reception path end 14.

The branch line coupler 22 is a form in which two transmission lines are connected by two branch lines, using a direct coupling method, and having four ports P1, P2, P3, and P4. The signal received from 21 is transmitted to the reception path end 25, and the signal transmitted from the transmission path end 24 is transmitted to the antenna 21.

However, since the transmission and reception separation units 11 and 21 are large in size, there is a problem in manufacturing a small RFID transmission and reception system, and since the price is high, the manufacturing cost increases.

The present invention provides an RFID transmission / reception system having excellent insertion loss characteristics and having high isolation between a transmitter and a receiver, thereby improving selectivity of a transceiver.

In addition, the present invention can stably restore / process the tag signal by eliminating the interference phenomenon between the tag signal or the interference between the tag signal and the noise component signal, and provides an RFID transceiver system with minimum interference between readers.

RFID transmitting and receiving system according to the present invention comprises a mixer unit for converting a signal received through the antenna terminal to an intermediate frequency signal; A signal limiter connected to the front end of the mixer to limit an interference signal by cutting out an area other than a carrier frequency of a received signal; And a controller which processes the transmitted / received signal into a digital signal and transmits a control signal to the signal limiter to provide a limiting reference for the interference signal.

Hereinafter, an RFID transmission and reception system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the embodiment of the present invention, the RFID transmission and reception system is implemented on a reader, and a UHF signal of a 900 MHz band is used as a carrier signal. Shall be used.

2 is a block diagram schematically showing the components of the RFID transmission and reception system 100 according to an embodiment of the present invention.

Referring to FIG. 2, the RFID transmission / reception system 100 according to the embodiment of the present invention includes an antenna 105, an Rx interference signal blocking unit 110, a signal limiting unit 120, a low noise amplifier (LNA) 125, Balloon circuit unit 130, the first mixer 135, the second mixer 140, the first phase synchronization circuit unit 145, the demodulation unit 150, the control unit 155, the modulator 160, the second phase synchronizer And a circuit unit 165, a voltage adjusting unit 175, a power amplifier module (PAM) 180, and a Tx interference signal blocking unit 185.

The Rx interference signal blocking unit 110 is connected between the antenna 105 and the signal limiting unit 120, transfers the signal received from the antenna 105 to the signal limiting unit 120, and feedback component of the received signal. To block.

The Tx interference signal blocking unit 185 is connected between the antenna 105 and the PAM 180, and the transmission signal transmitted from the PAM 180 passes through the antenna 105 and is reflected from the antenna 105 side. It blocks the feedback component of the transmission signal or the signal from the outside.

3 is a diagram illustrating an embodiment in which the Rx interference signal blocking unit 110 and the Tx interference signal blocking unit 185 of the RFID transmission and reception system 100 according to the embodiment of the present invention are implemented as diodes.

As shown in FIG. 3, the Rx interference signal blocking unit 110 and the Tx interference signal blocking unit 185 may be implemented as diodes, respectively, and the Rx interference signal blocking unit 110 may be a current flowing from the antenna 105. The polarity is connected so that forward vias are applied with respect to the Tx interference signal blocking unit 185, and the polarity is connected with reverse vias with respect to the current flowing from the antenna 105.

The signal limiting unit 120 serves to exclude the interference signal by cutting an area other than the carrier frequency of the received signal transmitted from the Rx interference signal blocking unit 110. .

4 is a view schematically showing the components of the signal limiting unit 120 of the RFID transmission and reception system 100 according to an embodiment of the present invention.

Referring to FIG. 4, the signal limiting unit 120 is composed of three circuits A, B, and C. The "A" circuit of the front end transmits a control signal from the control unit 155 (TP1 port). By controlling the current flowing to each capacitor and resistor due to transistor Q1, the power value of the tag signal in the analog state is kept in a stable range (to external interference).

The middle "B" circuit is a (±) compensation circuit of the tag signal, and serves to adjust the analog swing voltage up and down. It can be seen that the reference voltage is generated from the -5v power stage (-5VEE) at the top and the + 5V power stage J (+ 5VEE) at the bottom based on the comparison amplifier, and the tag signal transmitted from the "A" circuit is based on these. Boosts the swing voltage of the amplifier.

The latter "C" circuit performs a function of a limiter. When a control signal (TP2 port) is transmitted from the control unit 155, two transistors Q2 connected in parallel are not cut out and are kept in the frequency domain. The range of and cuts the region of the interference signal according to the region coupled to the coupled diode portion Q5.

5 is a graph measuring transmission and reception signals of the RFID transmission and reception system 100 according to an embodiment of the present invention, Figure 6 is a carrier frequency on which the transmission and reception signals of the RFID transmission and reception system 100 according to an embodiment of the present invention is carried out. It is a graph measured.

Referring to FIG. 5, the transmission signal and the reception signal are mixed together and passed through the Rx interference signal blocking unit 110, and the result of the measurement of the signal shape at this time can be seen, between the reference lines “C1” and “C2”. The signal B is an area of a tag signal, that is, a reception signal, and the area above the reference line "C1" and the area below "C2" are areas of the transmission signal.

The transmission signal may be a signal transmitted from the transmission path end, or may be a signal mixed with the reception signal transmitted and fed back through the antenna 105, or may be an external interference signal (hereinafter, for convenience of description, the " feedback transmission signal " ".

Since the feedback transmission signal has a power range of about 30 dBm and the reception signal has a power range of about -10 dBm, the reception signal is buried in the feedback transmission signal as shown in FIG. 5, thus making it difficult for the reception signal to be stably restored. do.

However, the signal limiter 120 cuts out the areas outside the reference lines "C1" and "C2", that is, the area of the feedback transmission signal (operated by a kind of band pass filter), and the carrier of the power range in which the tag signal exists. Since only the frequency is transmitted to the LNA 125, the received signal can be stably restored.

Referring to FIG. 6, a form in which a carrier frequency of a feedback transmission signal and a carrier frequency of a reception signal are mixed and transmitted together is illustrated. The signal limiter 120 removes an upper signal region based on a reference line “C3”. The signal area below "C3" is passed through.

The "A" signal measures a carrier frequency signal carrying a feedback transmission signal, and the "B" signal measures a carrier frequency signal carrying a reception signal.

The received signal filtered while passing through the Rx interference signal blocking unit 110 and the signal limiting unit 120 is transferred to the LNA 125, and the LNA 125 receives the received signal lowered due to attenuation and noise during the filtering process. Amplifies power at low noise.

The balloon circuit unit 130 separates the signal transmitted from the LNA 125 into an I signal (eg, "E sin ωt") and a Q signal (eg "E cos ωt"), that is, a single input signal is differential signal. To output.

Here, "Balun" is an abbreviation of "Balance-Unbalance", and means a circuit for converting a balanced signal into an unbalanced signal (or vice versa).

The output terminal of the balloon circuit unit 130 is connected to the first mixer 135 and the second mixer 140. The mixers 135 and 140 are dual mixers, and the first mixer 135 has a phase difference I. The intermediate frequency signals (I ⁺ signal and I ⁻ signal) are synthesized, and the second mixer 140 synthesizes the Q intermediate frequency signals (Q ⁺ signal and Q ⁻ signal) having a phase difference.

The first phase synchronization circuit unit 145 transmits the oscillation frequency signal to the first mixer 135 and the second mixer 140, so that the first mixer 135 receives the RF I signal transmitted from the balloon circuit unit 130. The intermediate frequency I signal is generated by synthesizing with the oscillation frequency signal, and the second mixer 140 generates the intermediate frequency Q signal by synthesizing the RF Q signal transmitted from the balloon circuit unit 130 with the oscillation frequency signal.

The demodulator 150 includes an analog to digital converter (ADC) to demodulate the intermediate frequency I signal and the intermediate frequency Q signal into digital signals having a plurality of polarities.

The control unit 155 includes a communication protocol to control wireless communication with the tag, and process the signal transmitted from the demodulator 150 as a digital signal or process the processed digital signal (eg, command data) by the voltage adjusting unit 175. To pass).

The controller 155 analyzes the code of the device identification information received from the tag. At this time, the controller 155 processes the filtering operation to convert the data format and extract necessary information. The controller 155 may be implemented using a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit.

In addition, the control unit 155 is connected to the signal limiting unit 120 and the voltage adjusting unit 175 to transfer the first control signal to the signal limiting unit 120 and the second control signal to the voltage adjusting unit 175. In this case, the signal limiting unit 120 is operated by determining whether the feedback transmission signal and the reception signal are mixed to transmit the first control signal.

In this case, as described above with reference to FIGS. 5 and 6, the controller 155 differentially sets a voltage range that is a reference for filtering (an operation of cutting out a signal of a predetermined power range) to set the signal limiter 120. It is possible to control the filtering operation of.

The voltage adjustor 175 adjusts the voltage of the digital transmission signal transmitted from the controller 155 and transmits the voltage to the modulator 160, and may be provided as a variable resistor.

The modulator 160 may include, for example, a mixer and a diode, and synthesizes a digital transmission signal transmitted from the voltage adjusting unit 175 with an oscillation frequency signal transmitted from the second phase synchronization circuit unit 165 and an analog signal. Modulation is performed with the transmission signal in the state.

In this case, the modulator 160 modulates according to a pulse-interval encoding (PIE) signal standard according to the UHF RFID Protocol such as ISO 18000-6A, ISO 18000-6B, ISO 18000-6C, and the like. According to an embodiment of the present invention, the RFID transmission / reception system 100 includes a double sideband-amplitude shift keying (DSB-ASK), a single sideband-amplitude shift keying (SSB-ASK), and a phase reversal-amplitude shift keying (PR-ASK). And a modulation scheme such as BPSK (Binary Phase Shift Keying) may be applied to a method of allocating a carrier phase differently according to information content of a digital signal.

7 is a graph illustrating reference voltage values set by the voltage adjusting unit 175 of the RFID transmission / reception system 100 according to an exemplary embodiment of the present invention to adjust the voltage of a digital signal.

The voltage range of the digital signal must be differentiated according to the modulation method of the modulator 160. Referring to FIG. 7, for example, in the case of BPSK, the digital signal is processed in a "D" section, that is, a voltage range of 0 V to x1 V. In the case of ASK, the digital signal must be processed in the "E" period, i.e., the voltage range of x2V to 0V.

In this case, the variables x1 and x2 may be different according to the type of the chip product of the controller. For example, in the case of a CMOS series chip, x1 may be set to 3V and x2 may be set to -3V. In the case of a TTL series chip, x1 may be 5V x2. Can be set to -5V.

Accordingly, the control unit 155 transmits the second control signal differentiated according to the type of modulation method and the digital signal transmitted by the control unit to the voltage adjusting unit 175, and the voltage adjusting unit 175 of the digital signal The voltage range is adjusted and transmitted to the modulator 160.

For example, when BPSK modulation is performed by a mixer, a diode, or the like, a digital signal having a voltage of about 0.7V to 3V corresponding to a diode forward voltage of the diode is generated by the voltage adjusting unit 175. In this case, the voltage adjusting unit 175 may have a variable value of about 0Ω to 1kΩ.

In addition, when the variable resistance value is adjusted to 180 Ω by the second control signal, a digital signal having a current value of about 13 mA is transmitted to the modulator 160.

Through such a process, the modulator 160 generates an analog transmission signal by mixing the oscillation frequency signal of the 900 MHz band transmitted from the second phase synchronization circuit unit 165 and the digital signal whose voltage value is adjusted, The transmission signal is transmitted to the PAM 180.

The PAM 180 includes at least one of a driving amplifier, an intermediate amplifier, a power amplifier, and a bias circuit to amplify a transmission signal in a state capable of outputting, and the amplified signal includes the Tx interference signal blocking unit 185 and the antenna ( Through 105) to the atmosphere.

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 exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications not illustrated in the drawings are possible. 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.

According to the RFID transmission / reception system according to the present invention, since the interference between the tag signal and the noise component signal (including the case where the transmitted signal acts as the noise component) can be stably restored / processed between the readers, the tag signal can be recovered and processed. There is an effect that communication can be performed without interference.

In addition, according to the present invention, since the separation circuit of the transmission and reception signal can be easily implemented using a basic device of low cost, the manufacturing cost of the RFID transmission and reception system can be lowered and the size of the product can be minimized.

Further, according to the present invention, the voltage of the transmission signal can be tuned on the same circuit in accordance with the chip type of the controller, so that there is no need to change the circuit or add a separate component.

Claims (12)

A mixer for converting a signal received through the antenna stage into an intermediate frequency signal; A signal limiter connected to the front end of the mixer to limit an interference signal by cutting out an area other than a carrier frequency of a received signal; An Rx interference signal blocking unit connected between the antenna terminal and the signal limiting unit and blocking a feedback component of the received signal; And And a control unit for processing a transmission / reception signal as a digital signal and transferring a control signal to the signal limiter to provide a range of the carrier frequency. The method of claim 1, wherein the signal limiting unit RFID transceiver system comprising a coupling coupled diode. The method of claim 1, wherein the signal limiting unit And a carrier frequency of the received signal cuts out signals in a power range that is larger or smaller than an existing power range. delete The method of claim 1, A power amplifier module for amplifying a transmission signal, And a Tx interference signal blocking unit connected between the power amplifier module and the antenna terminal to block an external signal including a feedback component of a transmission signal from being transmitted to the power amplifier module. The method of claim 1, wherein the Rx interference signal blocking unit RFID transceiver system comprising a diode. The method of claim 5, wherein the Tx interference signal blocking unit RFID transceiver system comprising a diode. The method of claim 1, A modulator for modulating the digital signal transmitted from the controller into an intermediate frequency signal in an analog signal state; And And a voltage adjusting unit connected between the modulating unit and the control unit to adjust a voltage of the digital signal and transmit the adjusted voltage to the modulating unit. 9. The apparatus of claim 8, wherein the control unit RFID transmission and reception system for transmitting a control signal to the voltage adjusting unit to adjust the voltage of the digital signal to various values. The method of claim 8, wherein the voltage adjusting unit RFID transmission and reception system comprising a variable resistor. The method of claim 8, wherein the modulator RFID transceiver system comprising a mixer, a diode. The method of claim 1, wherein the signal limiting unit A stabilization circuit for maintaining a power value of the received signal in a predetermined range; An adjusting circuit for adjusting an analog swing voltage of the received signal up and down; And And a limiter circuit that determines a signal area to be restricted and cuts out an area other than a carrier frequency of the received signal to limit an interference signal.

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