KR20110048423A - Transmitting and receiving device of rfid reader - Google Patents

Abstract

PURPOSE: A transmission and reception apparatus of an RFID reader is provided to offset a leakage signal according to the isolation of a discrete device in the usage of the other leakage signal. CONSTITUTION: A first circulator(130) transfers the transmission signal of a directivity combiner(120) through a first port and a second port to an antenna(140). The first circulator outputs a leakage signal about the transmission signal through a third port. A second circulator(150) receives the outputted first leakage signal of a combination port of a directional coupler through the first port. The second circulator receives the outputted second leakage signal of the third port through the second port.

Description

Transmitter and receiver of RFID reader {TRANSMITTING AND RECEIVING DEVICE OF RFID READER}

The present invention relates to an RFID reader, and more particularly, to an apparatus for transmitting / receiving an RFID reader for increasing the isolation between signals transmitted and received at a transceiver of an RFID reader.

RFID (Radio Frequency Identification) is applied to a wireless recognition system for transmitting and receiving data wirelessly in a predetermined frequency band, refers to an electronic chip containing a variety of information about the product.

The RFID system includes an RFID tag for storing data, a reader that reads data stored in the RFID tag through a transmitting antenna and a receiving antenna that transmits radio waves, or writes and reads predetermined data in the RFID tag. do.

Since the RFID reader transmits and receives at the same time, a transmission / reception isolation device for isolating a transmission signal and a reception signal is required, and a circulator or a directional coupler is usually used.

In order to improve reception sensitivity, it is necessary to increase the isolation of transmission / reception signals. However, since the isolation of a typical circulator or directional coupler is limited, even when using these elements, the signal at the transmitting end leaks to the receiving end to improve reception sensitivity. There will be a limit.

FIG. 1 is a diagram illustrating a general RFID reader transceiver. The transceiver 10 includes a power amplifier 11, a circulator 13, an antenna 17, and a low noise amplifier 19.

As shown, the transmission signal amplified and output through the power amplifier 11 is transmitted to the antenna 17 through the circulator 13, and the signal received by the antenna 17 is low noise through the circulator 13. Is passed to amplifier 19.

The circulator 13 transmits a signal transmitted from the power amplifier 11 to the antenna 17 and a signal received through the antenna 17 to the low noise amplifier 19.

However, the transmission signal amplified and output through the power amplifier 11 is leaked to the low noise amplifier 19 through the isolation port of the circulator, the leakage signal compared to the received signal received by the low noise amplifier 19 This is a very large signal, which reduces the reception sensitivity.

2 shows an example in which the directional coupler 15 is used instead of the circulator 13 of FIG. 1, and the directional coupler 15 also functions as the circulator 13.

Like the circulator 13, the directional coupler 15 also has a problem in that a leakage signal is generated and the reception sensitivity is lowered.

Therefore, since a leakage signal for a transmission signal is introduced into a receiver in a transmitting / receiving device which simultaneously transmits and receives, the reception sensitivity is lowered. Therefore, it is urgent to develop a technology that can improve the reception sensitivity by increasing the isolation between the transmission and reception signals.

The present invention provides a transceiver for an RFID reader that can improve reception sensitivity by canceling a signal leaking from a transceiver end of an RFID reader to another receiver through another leakage signal. It is for.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

Transmitting and receiving device of the present invention for achieving the above object, a power amplifier for amplifying and outputting the power of the input transmission signal; A directional coupler for outputting a transmission signal input from the power amplifier to an output port through an input port, and outputting a first leakage signal for the transmission signal to a coupling port; A first circulator for transmitting a transmission signal input from the directional coupler to a antenna through a first port and a second port, and outputting a second leakage signal for the transmission signal through a third port; And a first leakage signal output from the coupling port of the directional coupler to the first port, and a second leakage signal output from the third port of the first circulator to the second port. And a second circulator for canceling the second leakage signal.

Specifically, the second circulator outputs the first leakage signal input to the first port to the second port, and cancels the first leakage signal and the second leakage signal at the second port, and the first leakage signal. The signal and the second leakage signal are characterized in that they have the same amplitude and opposite phase.

The phase of the first leakage signal is the phase of the second circulator in phase ( Φ = 2π (L / λ) ) according to the path length L from the input port of the directional coupler to the first port of the second circulator. 2π / 3 ), and the path length L of the directional coupler and the second circulator is determined such that the phase of the first leakage signal is equal to that of the second leakage signal by π .

Another transmitting and receiving apparatus of the present invention for achieving the above object, a power amplifier for amplifying and outputting the power of the input transmission signal; Directional output of the transmission signal input from the power amplifier to the output port through the input port, outputting the first leakage signal for the transmission signal to the coupling port and the second leakage signal for the transmission signal to the isolation port Coupler; The first leakage signal output from the coupling port of the directional coupler is input to the third port, and the second leakage signal output from the isolation port of the directional coupler is input to the first port. A circulator for canceling out; And an attenuator provided between the coupling port of the directional coupler and the third port of the circulator to attenuate the first leakage signal.

In detail, the circulator may output a first leakage signal input to a third port to a first port, and cancel the first leakage signal and the second leakage signal at the first port.

Another transmitting and receiving apparatus of the present invention for achieving the above object, a power amplifier for amplifying and outputting the power of the input transmission signal; Outputting a transmission signal input from the power amplifier to an output port through an input port, outputting a first leakage signal for the transmission signal to a coupling port, and outputting a second leakage signal for the transmission signal to an isolation port; 1 directional coupler; And a first leakage signal output from the coupling port of the first directional coupler as a coupling port, and a second leakage signal output from the isolation port of the first directional coupler as an input port. And a second directional coupler for canceling the leakage signal, wherein the first leakage signal and the second leakage signal have the same amplitude and opposite phase.

As described above, by properly combining the circulator and the directional coupler in a device that simultaneously transmits and receives signals, the isolation between transmission and reception signals is canceled by canceling the leakage signals according to the unique isolation of a single device using different leakage signals. There is an advantage that can improve the receiving sensitivity by increasing the

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention. Like elements in the figures are denoted by the same reference numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

3 is a circuit block diagram illustrating an RFID reader transceiver according to an embodiment of the present invention. The transceiver 100 includes a power amplifier 110, a directional coupler 120, a first circulator 130, and an antenna. 140, a second circulator 150, and a low noise amplifier 160.

As shown, the power amplifier 110 amplifies and outputs the power of the input transmission signal.

The directional coupler 120 transmits the transmission signal input from the power amplifier 110 to the first circulator 130 through the input port PC11 and the output port PC12, the first circulator 130 is directional The transmission signal input from the combiner 120 is transmitted to the antenna 140 through the first port P11 and the second port P12, and the received signal received through the antenna 140 is transmitted to the second port P12. Transfer to the second circulator 150 through the third port (P13).

The second circulator 150 transmits the received signal input from the first circulator 130 to the low noise amplifier 160 through the second port P22 and the third port P23, and the low noise amplifier 160. Amplifies the weak received signal input from the third port P23 of the second circulator 150 while minimizing noise.

Looking at the transmission and reception device configured as described above in terms of the leakage signal, the directional coupler 120 outputs the transmission signal input from the power amplifier 110 to the output port PC12 through the input port PC11, the transmission signal The first leakage signal for the output through the coupling port (PC14).

The first circulator 130 transmits the transmission signal input from the directional coupler 120 to the antenna 140 through the first port P11 and the second port P12, and transmits a second signal to the transmission signal. The leakage signal is output through the third port P13.

The second circulator 150 receives the first leakage signal output from the coupling port PC14 of the directional coupler 120 to the first port P21 and the third port of the first circulator 130. The second leakage signal output from P13 is input to the second port P22 to cancel the first leakage signal and the second leakage signal.

In addition, the second circulator 150 outputs the first leakage signal input to the first port P21 to the second port P22, and the first leakage signal and the second leakage signal from the second port P22. The leakage signal is canceled out.

That is, the transmission signal output through the power amplifier 110 is transmitted to the antenna 140 via the directional coupler 120 and the first circulator 130. In addition, a part of the output power of the transmission signal flows into the second circulator 150 as a leakage signal due to the limit of the isolation degree of the first circulator 130.

Here, a second leakage signal having the same amplitude but opposite phase to the first leakage signal leaked from the directional coupler 120 is connected to the second port of the second circulator 150 through the first circulator 130. P22). In this case, the first leakage signal and the second leakage signal respectively input to the second circulator 150 cancel each other because they have the same amplitude but are out of phase with each other, and only the received signal received from the antenna 140 has a low noise amplifier 160. Will be displayed.

In the amplitude and phase of the first leakage signal, the amplitude of the first leakage signal is determined as the coupling degree of the directional coupler 120 and the phase is the path length from the directional coupler 120 to the second circulator 150. Or by inserting a phase delay element. That is, it is important that the first leak signal and the second leak signal have the same amplitude and the opposite phase so that the leak signal is canceled in the second circulator 150.

The amplitude of the output signal, that is, the first leakage signal, is determined according to the coupling degree of the directional coupler 120. The value of the first leakage signal must be equal to the second leakage signal. Since the degree of isolation is determined, the degree of coupling of the directional coupler 120 should be set equal to the degree of isolation of the first circulator 130.

The relationship between the path length L and the phase delay value Φ, the frequency f, and the wavelength λ for the first leakage signal and the second leakage signal to be in opposite phases is given by Equation 1 below. .

The first leak signal and the second leak signal are canceled at the second port P22 of the second circulator 150. The phase of the first leakage signal at the second port P22 of the second circulator 150 is from the input port PC11 of the directional coupler 120 to the first port P21 of the second circulator 150. Phase ( Φ = 2π (L3 / λ) ) according to the path length L3 of the sum of the phase ( 2π / 3 ) of the second circulator 150, that is, 2π (L / λ) + 2π / 3 [ rad], and the path length L3 of the directional coupler 120 and the second circulator 150 may be set such that the phase value of the first leakage signal is equal to the second leakage signal by π .

The phase of the second leakage signal is a path length L1 between the directional coupler 120 and the first circulator 130 and a path length L2 between the first circulator 130 and the second circulator 150. And it is determined by the phase delay of the first circulator 130.

If the characteristics of the antenna 140 are taken into consideration, the reflection characteristics of the antenna 140 and the path of the antenna also affect the magnitude and phase of the leakage signal and thus flow into the second port P22 of the second circulator 150. Measure the final amplitude and phase of the leakage signal to set the offset signal amplitude and path length.

In general, a transmission / reception apparatus for transmitting and receiving at the same time requires a transmission / reception isolation device for isolating a transmission signal and a reception signal. In order to improve the reception sensitivity, it is necessary to increase the isolation of the transmission and reception signals. However, since the isolation of a typical circulator or directional coupler is limited, even when using such a device, the signal at the transmitter end is partially leaked to the receiver, thereby limiting the improvement of the reception sensitivity. This will be.

Therefore, in the present invention, by configuring the leakage signal leaked from the transmitting end to be canceled by another leakage signal, it is possible to improve the isolation of the transmitting and receiving device to minimize the leakage of the leakage signal of the transmitting signal to the receiving end. Compared to the prior art, the reception sensitivity can be significantly improved.

Meanwhile, the leak signal described in the present invention includes a first leak signal and a second leak signal, wherein the first leak signal is a transmission combined signal for canceling leakage, and the second leak signal is a transmission leakage including a received signal. It is a signal.

4 is a circuit block diagram illustrating a transceiver for transmitting and receiving an RFID reader according to another embodiment of the present invention. The transceiver 200 includes a power amplifier 210, a directional coupler 220, an antenna 230, A circulator 240, an attenuator 250, and a low noise amplifier 260 are included.

As shown, the power amplifier 210 amplifies and outputs the power of the input transmission signal.

The directional coupler 220 transmits the transmission signal input from the power amplifier 210 to the antenna 230 and the reception signal received by the antenna 230 to the circulator 240.

The circulator 240 transmits the received signal transmitted from the directional coupler 220 to the low noise amplifier 260, and the low noise amplifier 260 amplifies the weak received signal transmitted from the circulator 240, but the noise is Minimize and amplify.

Then, the isolation port PC13 of the directional coupler 220 and the first port P11 of the circulator 240 are connected, and the coupling port PC14 of the directional coupler 220 and the circulator 240 are connected. A third port P13 is connected, and an attenuator 250 for attenuating the transmission signal is provided between the coupling port PC14 of the directional coupler 220 and the third port P13 of the circulator 240. have.

In FIG. 4, the isolation port PC13 of the directional coupler 220 is used as a reception path, which is different from that of FIG. 3. In this case, the circulator may be reduced to one different from FIG. 3.

Looking at the transmission and reception device 200 configured as described above from the side of the leakage signal, the directional coupler 220 outputs the transmission signal input from the power amplifier 210 to the output port PC12 through the input port PC11, The first leakage signal for the transmission signal is output to the coupling port PC14, and the second leakage signal for the transmission signal is output to the isolation port PC13, respectively. The second leakage signal includes a reception signal.

The circulator 240 inputs the first leakage signal output from the coupling port PC14 of the directional coupler 220 to the third port P13 and outputs it from the isolation port PC13 of the directional coupler 220. The second leakage signal is inputted to the first port P11 to cancel the first leakage signal and the second leakage signal.

The attenuator 250 is installed between the coupling port PC14 of the directional coupler 220 and the third port P13 of the circulator 240 to attenuate the first leakage signal.

That is, the first leakage signal for the transmission signal output from the power amplifier 210 is output to the coupling port PC14 of the directional coupler 220, and the second leakage signal for the transmission signal is combined with the reception signal. It is output to the isolation port PC13 of 220. The first leak signal and the second leak signal are equal in magnitude and opposite in phase, and are respectively introduced into the ports P13 and P11 of the circulator 240.

In the first port P11 of the circulator 240, the first leakage signal and the second leakage signal having different phases cancel each other. The magnitude of the first leakage signal is determined by the attenuator 250 and the phase is determined by the path length.

The method for determining the phase of the first leakage signal is the same principle as that of FIG. 3, but the amplitude of the first leakage signal output through the coupling port PC14 of the directional coupler 220 is usually the second leakage signal, that is, the interval. Since it is larger than the output signal of the report PC13, the first leakage signal is further attenuated by the formula "Attenuation degree = isolation degree of the directional coupler-coupling degree of the directional coupler" so that the amplitude of the first leakage signal and the second leakage signal are reduced. Configure the amplitudes of to match.

FIG. 5 is a circuit block diagram illustrating a transceiver for transmitting and receiving an RFID reader according to another embodiment of the present invention, wherein the transceiver 300 includes a power amplifier 310, a first directional coupler 320, an antenna 330, and a first device. It comprises a two-way coupler 340 and a low noise amplifier (350).

As shown, the power amplifier 310 amplifies and outputs the power of the input transmission signal.

The first directional coupler 320 transmits the transmission signal input from the power amplifier 310 to the antenna 330 and the received signal received by the antenna 330 to the second directional coupler 340.

The second directional coupler 340 transmits the received signal from the first directional coupler 320 to the low noise amplifier 350, and the low noise amplifier 350 transmits the weak received signal transmitted from the second directional coupler 340. Amplify while minimizing noise.

5 is different from FIG. 3 in that the isolation port PC13 of the first directional coupler 320 is used as a reception path, and that of two directional couplers 320 is different from FIG. 4.

Looking at the transmission and reception device configured as described above in terms of the leakage signal, the first directional coupler 320 outputs the transmission signal input from the power amplifier 310 to the output port PC12 through the input port PC11, The first leakage signal for the transmission signal is output to the coupling port PC14, and the second leakage signal for the transmission signal is output to the isolation port PC13, respectively. The second leakage signal includes a reception signal.

The second directional coupler 340 receives the second leakage signal output from the isolation port PC13 of the first directional coupler 320 to the input port PC21, the coupling of the first directional coupler 320 The first leakage signal output from the port PC14 is input to the coupling port PC22 to cancel the first leakage signal and the second leakage signal.

In the transmission / reception apparatus configured as described above, the first leakage signal for the transmission signal output through the power amplifier 310 is output to the coupling port PC14 of the first directional coupler 320 and output through the power amplifier 310. The second leakage signal for the transmitted signal is output to the isolation port PC13 of the first directional coupler 320 together with the received signal. The first leakage signal and the second leakage signal are equal in magnitude and opposite in phase to each port of the second directional coupler 340, and the first leakage signal and the second leakage signal are separated from the second directional coupler 340. Leakage signals cancel each other out.

The method for determining the phase of the second leakage signal is the same principle as in FIG. 3, and the magnitude of the first leakage signal is the sum of the coupling degree of the first directional coupler 320 and the coupling degree of the second directional coupler 340. Is determined. Therefore, in order to obtain the first leakage signal having the same amplitude as the second leakage signal, the magnitude of the second leakage signal, that is, the isolation of the first directional coupler 320, and the magnitude of the first leakage signal, that is, the first directional coupler 320 are obtained. What is necessary is just to comprise so that the synthetic coupling degree of the 2nd directional coupler 340 may be the same.

In general, since the isolation degree of the first directional coupler 320 is greater than the degree of coupling, extra attenuation is secured by the degree of coupling of the second directional coupler 340.

Accordingly, in the embodiment of the present invention, the leakage signal for the transmission signal is removed by the combination of the directional coupler 120 and the two circulators 130 and 150 as shown in FIG. 3, and the directional coupler 220 as shown in FIG. 4. And the leakage signal for the transmission signal is removed by the combination of one circulator 240 and the attenuator 250, and the leakage signal for the transmission signal by the combination of the two directional couplers 320 and 340 as shown in FIG. Will be removed.

As described above, in the present invention, by using the circulator and the directional coupler properly combined, the leakage signal according to the intrinsic isolation of a single device is canceled again to further increase the isolation between transmission and reception signals, thereby improving reception sensitivity.

In addition, although the transmission and reception apparatus of the present invention has been described as being applied to the RFID reader, it can be applied to the CW (Continuous Wave) radar to simultaneously transmit and receive. As such, even if the transmission and reception occurs simultaneously, such as an RFID reader or a CW radar, even if a transmission / reception isolation circuit is used, a part of the transmission signal that is overwhelmingly larger than the reception signal is leaked to the receiving end due to the limitation of isolation of the device. In addition, the isolation sensitivity between the transmitter and the receiver can be further increased than when using a single isolation device, thereby improving reception sensitivity.

Preferred embodiments of the present invention are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit of the present invention. Therefore, such modifications, changes and additions should be determined not only by the claims below, but also by equivalents to those claims.

1 and 2 are views illustrating a transmitting and receiving device of a general RFID reader, respectively.

3 is a circuit block diagram illustrating an apparatus for transmitting and receiving an RFID reader according to an embodiment of the present invention.

4 is a circuit block diagram illustrating an apparatus for transmitting and receiving an RFID reader according to another embodiment of the present invention.

5 is a circuit block diagram showing an apparatus for transmitting and receiving an RFID reader according to another embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

100: transceiver 110: power amplifier

120: directional coupler 130: first circulator

140: antenna 150: second circulator

160: low noise amplifier

Claims (11)

A power amplifier for amplifying and outputting the power of the input transmission signal; A directional coupler for outputting a transmission signal input from the power amplifier to an output port through an input port and outputting a first leakage signal for the transmission signal to a coupling port; A first circulator for transmitting a transmission signal input from the directional coupler to a antenna through a first port and a second port, and outputting a second leakage signal for the transmission signal through a third port; And The first leakage signal output from the coupling port of the directional coupler is input to the first port, and the second leakage signal output from the third port of the first circulator is input to the second port. And a second circulator for canceling the leakage signal. 2. The method of claim 1, And the second circulator outputs a first leakage signal input to a first port to a second port, and cancels the first leakage signal and the second leakage signal at the second port. The method of claim 1, And the first leakage signal and the second leakage signal have the same amplitude and opposite phase. The method of claim 3, wherein The phase of the first leakage signal is the phase of the second circulator in phase ( Φ = 2π (L / λ) ) according to the path length L from the input port of the directional coupler to the first port of the second circulator. 2π / 3 ) plus And the path length (L) of the directional coupler and the second circulator is determined such that the phase of the first leakage signal is out of phase with the second leakage signal by π . The method of claim 1, And a signal received through the antenna is transmitted to the second port of the second circulator through the second port and the third port of the first circulator. A power amplifier for amplifying and outputting the power of the input transmission signal; Directional output of the transmission signal input from the power amplifier through the input port to the output port, the first leakage signal for the transmission signal to the coupling port and the second leakage signal for the transmission signal to the isolation port Coupler; The first leakage signal output from the coupling port of the directional coupler is input to the third port, and the second leakage signal output from the coupling port of the directional coupler is input to the first port. A circulator for canceling out; And And an attenuator disposed between the coupling port of the directional coupler and the third port of the circulator to attenuate the first leakage signal. The method of claim 6, The circulator outputs the first leakage signal input to the third port to the first port, and the first reader and the transceiver for transmitting and receiving the first leakage signal and the second leakage signal. The method of claim 6, And the first leakage signal and the second leakage signal have the same amplitude and opposite phase. The method of claim 6, And a signal received through the antenna is transmitted to the first port of the circulator through the output port and the isolation port of the directional coupler. A power amplifier for amplifying and outputting the power of the input transmission signal; Outputting a transmission signal input from the power amplifier to an output port through an input port, outputting a first leakage signal for the transmission signal to a coupling port, and outputting a second leakage signal for the transmission signal to an isolation port; Monodirectional coupler; And The first leakage signal output from the coupling port of the first directional coupler is input to the coupling port, and the second leakage signal output from the isolation port of the first directional coupler is input to the input port. And a second directional coupler for canceling the leakage signal. And the first leakage signal and the second leakage signal have the same amplitude and opposite phase. 11. The method of claim 10, And a signal received through the antenna is transmitted to the input port of the second directional coupler through the output port and the isolation port of the first directional coupler.

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