KR20070096713A - Transmitting and receiving system of radio frequency identification - Google Patents

Abstract

An RFID(Radio Frequency Identification) transmission/reception system is provided to improve receive sensitivity by supplying a reference frequency signal only to one of a transmission stage and a reception stage, rather than to both sides, and reduce the likelihood of malfunction by restraining a spurious phenomenon at the reception stage. A TX(Transmission) BB(baseband) processing unit(130) converts a baseband transmission signal into an RF transmission signal and processes it. An RX(Reception) BB processing unit(170) converts an RF reception signal into a baseband reception signal and processes it. A PLL(Phase Locked Loop)(160) provides a reference frequency signal for the conversion of the baseband reception signal or the conversion of the RF transmission signal to the baseband processing unit(170). A switch(150) connects the PLL(160) to the TX BB processing unit(130) and the RX BB processing unit(170), and selectively transfers the reference frequency signal.

Description

Transmitting and receiving system of Radio Frequency IDentification

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

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

Figure 3 is a block diagram schematically showing the components of the switch provided in the RFID transmission and reception system according to an embodiment of the present invention.

4 is a block diagram schematically illustrating the components of a transmitting RF processor and a transmitting baseband processor of an RFID transceiver system according to an embodiment of the present invention.

FIG. 5 is a block diagram schematically illustrating components of a receiving RF processor and a receiving baseband processor included in an RFID transceiver system according to an exemplary embodiment of the present invention. FIG.

Figure 6 is a graph measuring the voltage of the transmission and reception signals processed by the RFID transmission and reception system according to an embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

100: RFID transmission and reception system according to the present invention

105: first antenna 110: second antenna

120: transmitting RF processing unit 130: transmitting baseband processing unit

140: control unit 150: switch

152: control logic circuit 152a: power supply terminal

152b, 152c: control voltage terminal 154: switch circuit

160: phase synchronization circuit 170: receiving baseband processing unit

180: receiving RF processing unit

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

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.

In general, a commercial RFID system consists of an RFID tag attached to a product and embedded with details, an RFID reader that reads information of the RFID tag using RF communication, and the RFID tag attached to the product is located at which the RFID reader is located. Since information is transmitted through RF communication through the region, it provides a foundation for efficiently managing logistics / distribution such as distribution, assembly, price change, and sales of goods.

On the other hand, the reading distance and recognition rate of the RFID tag are greatly influenced by the feedback component of the transmission power of the RFID reader. In the conventional RFID reader, the isolation between the transmitting end and the receiving end is reduced, and frequency separation is difficult. Since there is no way to suppress the feedback component, it is difficult to filter the frequency signal of the corresponding band.

In particular, when receiving the reference frequency signal from the phase synchronization circuit and mixing the baseband reception signal or the RF transmission signal, the feedback component signals are easily introduced into each other's signal paths between the transmitter and the receiver, thereby providing energy to the tag and There is a problem that the recognition rate is unstable.

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, an RFID reader usually has an effective lsotropic radiated power of 1 W (EIRP). For example, EIRP is called "isotropic radiated power", which is a measure of the power of the antenna main beam with respect to the isotropic radiator. Multiplied by the gain in the given direction for the isotropic antenna).

However, when a reference frequency signal is supplied from one phase synchronization circuit, a part of a transmission signal having an output of about 1 W is introduced into the receiver, which causes the reference frequency signal to flow when switched to the reception mode.

Therefore, as described above, the reference frequency signal may flow in the reception mode to generate a power-fogging state. In this case, the signal may not be properly processed or the device may be damaged.

According to the present invention, when the receiving end and the transmitting end receive a reference frequency signal together from one phase synchronization circuit, the RFID communication uses a half-duplex communication method. Provided is an RFID transceiver system which improves the isolation of the transmitter.

According to an aspect of the present invention, there is provided an RFID transmission / reception system including: a transmission side baseband processor configured to convert a baseband transmission signal into a radio frequency (RF) transmission signal and process the signal; A receiving side baseband processor for converting and processing an RF received signal into a baseband received signal; A phase synchronization circuit for providing a reference frequency signal to the baseband processor for converting the baseband received signal or converting the RF transmission signal; And a signal separation unit connecting the phase synchronization circuit, the transmission side baseband processor and the reception side baseband processor, and selectively transferring the reference frequency signal.

The signal separation unit of the RFID transceiver system according to the present invention transmits the reference frequency signal to a receiving side baseband processor when an RFID signal is received, and transmits the reference frequency signal to a transmitting side base when the RFID signal is transmitted. Transfer to the band processor.

In addition, the RFID transmission and reception system according to the present invention further includes a control unit for generating a transmission signal as a digital signal or processing the signal when the baseband reception signal is converted into a digital signal, and the signal separation unit applies a control signal from the control unit. Receive the switching operation.

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

1 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. 1, an RFID transceiver system 100 according to an exemplary embodiment of the present invention includes a first antenna 105, a second antenna 110, a transmission (Tx) radio frequency (RF) processor 120, and a transmission (Tx). A baseband processor 130, a controller 140, a phase synchronization circuit 160, a switch 150, a receive (Rx) baseband processor 170, and a receive RF processor 180 are included.

First, the reception RF processing unit 180 filters / amplifies a received signal transmitted through the second antenna 110 as an RF signal, and the reception baseband processing unit 170 is connected to a phase synchronization circuit 160. The baseband received signal is generated by receiving the reference frequency signal from the 150 and mixing the received RF signal.

The receiving baseband processor 170 filters / amplifies the baseband received signal, converts it to AD (Analog to Digital), and transmits the same to the controller 140.

The control unit 140 controls wireless communication with the RFID tag, processes the signal transmitted from the reception baseband processing unit 170 as a digital signal on the application layer, or transmits the processed digital signal to the transmission baseband processing unit 130. To pass.

The transmission baseband processor 130 receives the digital signal from the controller 140 and performs DA conversion processing, and filters / amplifies the transmission signal converted into an analog signal.

When the baseband transmission signal is filtered / amplified, the transmission baseband processing unit 130 receives the corresponding reference frequency signal from the switch 150 and generates an RF transmission signal by mixing with the baseband transmission signal.

When the RF transmission signal is generated, the transmission RF processing unit 120 filters / amplifies it and transmits it through the first antenna 105.

In the embodiment of the present invention, the phase synchronization circuit 160 is divided into two for the receiving end and the transmitting end, not provided in two, provided as one is connected to the switch 150.

The switch 150 has one input terminal connected to the phase synchronization circuit 160 and two output terminals connected to the transmitting baseband processor 130 and the receiving baseband processor 170, respectively.

In general, the RFID tag and the RFID reader request information and provide information in response to the information, that is, the half duplex communication, so that the phase synchronization circuit 160 transmits the baseband processor 130. And it is not necessary to simultaneously provide the reference frequency signal to the receiving baseband processing unit 170.

Accordingly, when the phase synchronization circuit 160 supplies the reference frequency signal constantly, the switch 150 transmits the reference frequency signal to the receiving baseband processor 170 in accordance with a situation, that is, when the received signal is processed. When the transmission signal is processed, the reference frequency signal is transmitted to the transmission baseband processor 130.

In this case, the switch 150 receives a control signal (voltage) from the control unit 140 to perform a switching operation. For example, when the control unit 140 generates a transmission signal and transmits it to the transmission baseband processor 130. If so, the control signal for selecting a signal path to the transmission baseband processing unit 130 is transferred, and in other cases, the control signal for selecting the signal path to the reception baseband processing unit 170 is transmitted to maintain the standby state. Can be.

The configuration and operation of the switch 150 will be described later in more detail with reference to FIG. 3.

2 is a block diagram schematically illustrating the components of the phase synchronization circuit 160 included in the RFID transceiver system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the phase synchronization circuit 160 includes a TCXO (Temperature Compensated X-tal Oscillator) 161, a frequency detector 162, a charge pump 163, a loop filter 164, and a VCO ( Voltage Controlled Oscillator) 165, and a divider 166 is configured.

The TCXO 161 is a circuit having a crystal oscillator and controlling frequency disturbance according to a temperature change. The TCXO 161 transmits an oscillation frequency signal having a constant value of frequency to the temperature change to the frequency detector 162.

The frequency detector 162 detects a reference frequency signal output from the VCO 165 and compares it with an oscillation frequency signal transmitted from the TCXO 161.

In general, the reference frequency signal is a high frequency (eg, frequency signal in "㎓") signal, and the oscillation frequency signal is a relatively low frequency signal (eg, frequency signal in "MHz" unit) compared to the reference frequency signal.

Accordingly, the divider 166 converts the reference frequency signal to a relatively low frequency in order to convert the reference frequency signal output from the VCO 165 into a magnitude comparable with the oscillation frequency signal.

For example, if the TCXO 161 provides an oscillation frequency signal of 100 MHz and the VCO 165 provides a reference frequency signal of 1.1 kHz, the divider 166 converts the reference frequency signal to a size of 1/10. Switch.

The frequency detector 162 compares the frequency of the oscillation frequency signal and the converted reference frequency signal and transfers a control signal corresponding to the frequency difference to the charge pump 163 and the charge pump 163 supplies a current value according to the control signal. Adjust

The charge pump 163 is an electronic circuit that supplies or absorbs a specific amount of charge according to a control signal. When the voltage of the reference frequency signal is larger than the oscillation frequency signal, the charge pump 163 transfers a specific amount of charge by the branch circuit to the loop filter 164. If the voltage of the reference frequency signal is smaller than the oscillation frequency signal, the branch circuit draws a certain amount of charge from the loop filter 164.

The loop filter 164 may filter a signal of a noise component mixed on the charge pump 163, for example, using a secondary filter including a plurality of capacitors and resistors.

In the capacitor connected in parallel with the resistor, the amount of charge and push of the charge pump 163 is adjusted to adjust the voltage of the VCO 165 and to reduce the spurious characteristics generated on the phase synchronization circuit 160.

The VCO 165 includes a resonator, a power supply (not shown), and the like, and resonates a reference frequency signal without shaking in accordance with a control signal passed through the loop filter 164.

Thus, for example, the reference frequency signal is minutely flowed due to external environmental change factors such as temperature to become unstable, and distortion of the intermediate frequency signal can be prevented.

3 is a block diagram schematically illustrating the components of the switch 150 provided in the RFID transmission and reception system 100 according to an embodiment of the present invention.

Referring to FIG. 3, the switch 150 includes a control logic circuit 152, a switch circuit 154, a power terminal (Vcc) 152a, a first control terminal (Vctrl1) 152b, and a second control terminal (Vctrl2). 152c).

The control logic circuit 152 is connected to the power supply terminal 152a, the first control terminal 152b and the second control terminal 152c to receive a signal, the power supply terminal 152a is the control logic circuit 152 And a terminal to which a power source of the switch circuit 154 is input, and the control terminals 152b and 152c are terminals to which a control voltage of a switching operation is input.

A control voltage is applied through the two control terminals 152b and 152c, and the control logic circuit 152 analyzes a combination (logical operation) of the applied control voltages to generate a decoded signal.

The switch circuit 154 receives the decoding signal from the control logic circuit 152 and opens and closes the five signal paths according to the decoding signal. Accordingly, the phase synchronization circuit 160 may be selectively connected to any one of the baseband processor of the transmitting baseband processor 130 and the receiving baseband processor 170.

4 is a block diagram schematically illustrating the components of the transmitting RF processing unit 120 and the transmitting baseband processing unit 130 included in the RFID transmitting and receiving system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the transmitting RF processor 120 includes a power amplifier (PA) 122, an intermediate amplifier (IA) 124, and a voltage gain amplifier (VGA) connected to an antenna. 126, a second band pass filter 128, and the transmission baseband processor 130 includes a synthesizer 137, a first mixer 135, a second mixer 136, and a first BB; A baseband filter 133, a second BB filter 134, a first digital to analog converter 131, and a second DA 132 are included.

When the controller 140 processes a digital signal such as an information request signal, an I-phase signal and a Q-quad-phase signal, which are digital signal states, are transmitted through the first DA 131 and the second DA 132. Each of the first BB filter 133 and the second BB filter 134 is converted into an analog signal and filters the noise component mixed on the baseband I transmission signal and the baseband Q transmission signal during the conversion process.

The first mixer 135 and the second mixer 136 receive the reference frequency signal from the switch 150, and mix the baseband I transmission signal and the baseband Q transmission signal with the reference frequency signal, respectively, to the RF I transmission signal. And an RF Q transmission signal.

As described above, the switch 150 has two output paths (paths connected to the transmission baseband processor 130 and paths connected to the reception baseband processor 170), and each output path is branched into two again. In the case of the path connected to the transmission baseband processor 130, the first mixer 135 and the second mixer 136 are connected, and in the case of the path connected to the reception baseband processor 170, the third mixer and the fourth mixer are connected to each other. The third mixer and the fourth mixer (see FIG. 5).

The synthesizer 137 combines the RF I transmission signal and the RF Q transmission signal to generate one RF signal, and the RF transmission signal undergoes an amplification process through the first band pass filter 128.

The voltage gain amplifier 126 amplifies the RF transmission signal by adjusting the gain by a control voltage. Through this function, the gain is automatically controlled according to the electric field strength of the high frequency input signal applied to the antenna terminal. The output of is kept constant.

The voltage-gain-amplified RF transmission signal is sequentially amplified on the intermediate amplifier 124 and the power amplifier 122, and finally amplified into a signal of a size that can be transmitted through the antenna.

In general, the above-described voltage gain control (VGC) method is used in the medium and weak electric field areas because it has a correlation with the electric field strength of the amplifier stage.

5 is a block diagram schematically illustrating the components of the receiving RF processor 180 and the receiving baseband processor 170 included in the RFID transceiver system 100 according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the reception RF processing unit 180 includes a band pass filter (BPF) 182 and a low noise amplifier (LNA) 184, and the reception baseband processing unit 170. ) Is a balun circuit 179, a third mixer 177, a fourth mixer 178, a first low pass filter (LPF) 175, a second low band filter 176, and a first BA ( A baseband amplifier 173, a second BA 174, a first analog to digital converter 171, and a second AD 172 are included.

The second band pass filter (usually used as a saw filter) 182 filters only the received signal of the corresponding RFID band among the signals received through the second antenna 110.

Since the power of the signal at this time has a very low power level due to the effects of attenuation and noise, the low noise amplifier 184 amplifies the filtered received signal. Since the received signal contains external noise, the noise component is maximized. It is suppressed and the received signal is amplified.

In other words, an important part of determining the noise figure of the communication system is the noise figure of the early block of the system because the overall noise figure is greatly improved when the early block has a small noise figure and a large gain. Therefore, the low noise amplifier is designed by catching the operating point and the matching point so that the noise figure has a small value.

The balun circuit 179 separates the RF reception signal transmitted from the transmission RF processing unit 130 into an I signal and a Q signal. 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 balun circuit 179 has an output terminal connected to a third mixer 177 and a fourth mixer 178, respectively, when I and Q signals using the same transmission band are present, making one side GND and the other side a signal. By driving (which is a kind of signal conversion), I or Q signals are separated.

The balun circuit 159 may be implemented through a line combination, a lumped element, a resonant waveguide method, or the like.

The third mixer 177 and the fourth mixer 178 receive the reference frequency signal from the switch 150, and combine the separated RF I received signal and RF Q received signal with the baseband I received signal and the baseband. Generated by Q received signal.

The baseband I received signal and the baseband Q received signal are respectively passed through the first low band filter 175 and the second low band filter 176 to remove the noise component mixed in the mixing process, and to remove the first BA 173 and the first BA 173. Medium frequency amplification via the second BA (174).

The intermediate frequency amplified baseband I received signal and the baseband Q received signal are converted into digital signals by the first AD (Analog to Digital converter) 171 and the second AD 172, respectively, and the controller 140 receives the received signals. Interpret and process on the application layer.

The control unit 140 has a communication protocol to control wireless communication with the RFID tag, and analyzes the code of the tag identification information received from the RFID tag. At this time, the data format is converted and filtering is performed to extract necessary information. Process.

The controller 140 may use a field programmable gate array (FPGA) circuit or a digital signal processing (DSP) circuit, and the FPGA circuit may add programming as needed when implementing a function of an RFID reader beyond a chip production process. Means a gate array circuit (logical integrated circuit) that can be.

In addition, a DSP (Digital Signal Processing) circuit is a circuit that performs algebraic processing on digital data obtained by A / D conversion of an analog signal and filters or performs signal processing such as spectrum analysis.

6 is a graph measuring the voltage of the transmission and reception signal processed by the RFID transmission and reception system 100 according to an embodiment of the present invention.

Referring to FIG. 6, voltages of signals processed by the RFID transmission / reception system 100 according to an exemplary embodiment of the present invention are measured. In particular, when a signal is transmitted from a reader, the signal voltage A of the transmitter is 25 dB or more. Measured by the power, it can be confirmed that the signal voltage at the receiving end, that is, the voltage B of a part of the transmitted signal introduced into the receiving end has been reduced to a significant value of 3 dB to 4 dB or less.

This can be interpreted that the reference frequency signal is stably supplied without flow, and the isolation between the transmitter and the receiver is improved.

Although the present invention has been described above with reference to the embodiments, these are only examples and are not intended to limit the present invention, and those skilled in the art to which the present invention pertains may have an abnormality within the scope not departing from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not illustrated. 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 transmission and reception system according to the present invention, it is possible to improve the isolation between the transmitting end and the receiving end to improve the transmission / reception data error rate, stability, recognition distance, etc. according to the change of the radio wave environment.

In addition, according to the present invention, since the reference frequency signal is not supplied to the transmitting end and the receiving end in parallel, and is supplied only to one place in some cases, the reception sensitivity can be improved by 3 to 4 dB or more (25 dB or more in the case of a transmitted signal). By suppressing the occurrence of spurious phenomenon at the receiving end it is possible to reduce the probability of malfunction.

Claims (4)

A transmission side baseband processor for converting and processing a baseband transmission signal into a radio frequency (RF) transmission signal; A receiving side baseband processor for converting and processing an RF received signal into a baseband received signal; A phase synchronization circuit for providing a reference frequency signal to the baseband processor for converting the baseband received signal or converting the RF transmission signal; And And a signal separator which connects the phase synchronization circuit, the transmitting baseband processor and the receiving baseband processor, and selectively transmits the reference frequency signal. The method of claim 1, wherein the signal separation unit RFID transmitting and receiving system, characterized in that provided as a single pole double throw (SPDT) switch element. The method of claim 1, wherein the signal separation unit And when the RFID signal is received, transmits the reference frequency signal to the receiving side baseband processor, and when the RFID signal is transmitted, transmits the reference frequency signal to the transmitting side baseband processor. The method of claim 1, A control unit for generating a transmission signal as a digital signal or converting the baseband reception signal into a digital signal is further provided. And the signal separation unit receives a control signal from the controller to perform a switching operation.

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