JP2010041189A - Leakage signal cancellation circuit, and transceiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leakage signal cancellation circuit hardly causing interference of a leakage signal to a response signal regardless of a modulation method of the response signal and capable of reducing degradation of reception sensitivity; and a transceiver using the same. <P>SOLUTION: This leakage signal cancellation circuit is provided with a cancellation signal switch 211 for turning on/off input of a cancellation signal to a synthesizer 205, and the cancellation signal switch 211 is turned off when a response signal is a sub-carrier modulation signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a leakage signal cancellation circuit used for an interrogator of a radio identification system, for example, and a transceiver using the same.

  For example, in a conventional leakage signal cancellation circuit in an interrogator of a wireless identification system, a part of a transmission signal is extracted by a coupler, and the amplitude and phase of the extracted signal are adjusted by a quadrature modulator and leaked from a transmission unit to a reception unit. A cancellation signal having the same amplitude as that of the leakage signal to be input and a reverse phase is generated and combined with the reception signal including the leakage signal to cancel the leakage signal (see, for example, Non-Patent Document 1).

  This circuit performs the following operation. During transmission, a leakage signal leaks from the transmission unit to the reception unit. In the leakage signal canceling circuit, a part of the transmission signal is extracted, and the canceling signal is generated by adjusting the amplitude and phase in the quadrature modulator or the vector modulator as follows.

  First, feedback control is performed so that the cancellation signal has the same amplitude and the same phase as the reception signal based on the comparison result of the amplitude and phase of the reception signal including the leakage signal and the cancellation signal. Then, the cancellation signal output from the quadrature modulator or the vector modulator and the reception signal are combined in reverse phase to cancel the leakage signal leaking into the reception unit.

  In the wireless identification system, the interrogator transmits an unmodulated carrier to power the responder, while the responder turns on and off the reflection of the unmodulated carrier transmitted by the interrogator and returns a response signal. Therefore, the interrogator receives the response signal from the responder while transmitting the unmodulated carrier wave.

  In an actual interrogator, even when an unmodulated carrier wave is transmitted, the carrier wave undergoes some amplitude modulation due to the thermal noise of the transmitter and the power supply noise of the power amplifier. As a result, the spectrum of the transmission signal extends to the response signal band near the carrier wave, that is, the reception signal band.

  Therefore, when the transmission signal leaks to the reception unit, there is a problem that the reception sensitivity is deteriorated due to interference with the reception signal (see, for example, Non-Patent Document 2). In such a case, if a leakage signal cancellation circuit using a vector modulator is provided, the leakage signal subjected to amplitude modulation can be canceled, so that interference with the reception signal due to the leakage signal is suppressed and reception sensitivity is deteriorated. Can be improved.

  By the way, in the wireless identification system, the baseband modulation method in which the responder responds using the same band as the transmission modulation signal band of the interrogator, the response signal of the responder is subcarrier modulated, and the transmission modulation signal of the interrogator There is a method of subcarrier modulation that responds using a band immediately outside the band. The latter method separates the band of the interrogation signal originally transmitted by the interrogator and the response signal of the transponder, and reduces interference to the transponder by another interrogator that is not involved in communication.

  The above-described problem that the unmodulated carrier wave is modulated by the noise of the transmitter and the spectrum of the transmission signal broadens and interferes with the response signal of the responder is particularly noticeable in a system that employs the former baseband modulation method. . On the other hand, in a system employing the latter subcarrier modulation method, the response signal of the responder uses an outer band away from the carrier wave transmitted by the interrogator, and thus is less susceptible to interference (for example, Non-Patent Document 2). (See FIG. 5).

P.D.L.Beasley A.G.Stove B.J.Reits and B-O.As, "Solving the problems of a single antenna frequency modulated CW radar", Record of the IEEE 1990 International Radar Conference, 7-10 May 1990, P391 ~ 395, Figure 1, Figure 2 Ryoji Hayashi, Kazutoshi Mori, “Communication distance of UHF band RFID passive tag system and its improvement” IEICE General Conference 2008-12-12

  As described above, the radio identification system includes a baseband modulation method and a subcarrier modulation method, and systems to which these methods are applied are mixed. In an interrogator having a conventional leakage signal canceling circuit, the output of a circuit that generates a canceling signal is always connected to a combiner that combines the received signal and the canceling signal. That is, regardless of which modulation method is used, the response signal (received signal) of the responder is combined with the canceling signal via the leakage signal canceling circuit, and then input to the receiving unit and received.

  In such a configuration, thermal noise generated from the quadrature modulator or vector modulator in the circuit that generates the cancellation signal, the level adjustment amplifier, or the like enters the reception signal via the synthesizer. Normally, thermal noise generated by the quadrature modulator or vector modulator in the leaky signal cancellation circuit and loss of the combiner are large, and the SN ratio of the received signal is deteriorated by passing through the leaky signal cancellation circuit.

  When the response signal is based on the baseband modulation, the effect of canceling the leaked signal and reducing interference with the response signal is greater than the deterioration of the reception signal-to-noise ratio due to passing through the leaky signal cancellation circuit. On the other hand, when the response signal is a subcarrier modulation system, the interference that the original transmission leakage signal gives to the response signal is small, so if the reception signal-to-noise ratio deteriorates via the leakage signal cancellation circuit, it does not pass through the leakage signal cancellation circuit. On the contrary, reception sensitivity deteriorates.

  The present invention has been made in order to solve the above-described problems, and a leakage signal cancellation circuit capable of reducing leakage signal interference to a response signal and reducing deterioration of reception sensitivity irrespective of a modulation method of the response signal. And it aims at obtaining the transmitter / receiver using this.

  A leakage signal cancellation circuit according to the present invention is provided in a transmitter / receiver having an interrogator and a responder, and in the leakage signal cancellation circuit for canceling a leakage signal to a reception signal of a transmission signal, the cancellation signal and the reception signal are synthesized. And a synthesizer for canceling the leakage signal, and a cancellation signal switch for turning on and off the input of the cancellation signal to the synthesizer according to the modulation method of the response signal of the responder. is there.

  According to this invention, the cancellation signal switch for turning on / off the input of the cancellation signal to the combiner is provided, and if the response signal of the responder is a subcarrier modulation signal, the cancellation signal switch is turned off. In this case, the interference of the leaked signal is reduced via the leaky signal cancellation circuit. In the case of the subcarrier modulation method, the reception sensitivity can be maintained without passing through the leaky signal cancellation circuit, and the response signal is modulated. Regardless of the method, there is an effect that the signal can be demodulated well on the interrogator side.

Embodiment 1 FIG.
1 is a diagram showing a configuration of a transceiver including a leakage signal cancellation circuit according to Embodiment 1 of the present invention. 1 includes a transmission unit 101, a local oscillator 102, mixers 103 and 106, a power amplifier 104, a circulator 105, a high-pass filter (HPF) 107, a reception unit 108, a coupler 201, a quadrature modulator 202, and a distribution. Generators 203 and 204, combiner 205, cancellation signal switch 211, amplitude comparator 301, phase comparator 302, A / D converters (ADC) 303 and 304, integrators 305 and 306, Cartesian coordinate converter 307, and D / A converters (DACs) 308 and 309 are provided.

  Further, the integrators 305 and 306 and the orthogonal coordinate conversion unit 307 are a digital unit 311 that processes a digital signal. The digital section 311, the amplitude comparator 301, the phase comparator 302, the ADCs 303 and 304, and the DACs 308 and 309 constitute a signal comparison unit 300. The coupler 201, the quadrature modulator 202, the distributors 203 and 204, the combiner 205, the cancellation signal switch 211, and the signal comparison unit 300 realize a leakage signal cancellation circuit that cancels the leakage signal.

  The transmitting unit 101 outputs a baseband or intermediate frequency transmission signal. The local oscillator 102 oscillates a local oscillation signal as a carrier wave. The mixer 103 multiplies the baseband or intermediate frequency transmission signal output from the transmission unit 101 with the local oscillation signal output from the local oscillator 102, and performs on / off modulation of the carrier wave. The power amplifier 104 is an amplifier that amplifies the transmission signal.

  The circulator 105 is a circulator for supplying a transmission signal output from the power amplifier 104 to an antenna (not shown) and extracting a reception signal from the antenna. The mixer 106 multiplies the received signal by the local oscillation signal output from the local oscillator 102 and converts it into a baseband or intermediate frequency received signal.

  The receiving unit 108 processes the baseband or intermediate frequency received signal that has been frequency-converted by the mixer 106. The HPF 107 is a filter for removing only a high frequency band signal from the signal output from the mixer 106 and removing a DC component.

  The coupler 201 is a coupler that extracts a part of the transmission signal output from the power amplifier 104. The quadrature modulator 202 adjusts the amplitude and phase of the transmission signal extracted by the coupler 201 to generate an offset signal. For example, the cancellation signal is generated based on the I and Q signals output from the signal comparison unit 300.

  The distributor 203 is a distributor that distributes the cancellation signal output from the quadrature modulator 202 in reverse phase, and the distributor 204 is a distributor that extracts a part of the received signal before being combined with the cancellation signal by the combiner 205. is there. The combiner 205 combines the output signal of the distributor 203 and the received signal. The amplitude comparator 301 is a comparator that compares the amplitude of the cancellation signal output from the distributor 203 and the received signal output from the distributor 204. The phase comparator 302 is a comparator that compares the phases of the cancellation signal output from the distributor 203 and the received signal output from the distributor 205.

  The ADC 303 A / D converts the amplitude difference signal output from the amplitude comparator 301. The ADC 304 A / D converts the phase difference signal output from the phase comparator 302. The integrator 305 is an integrator that integrates the amplitude difference signal output from the ADC 303. The integrator 306 is an integrator that integrates the phase difference signal output from the ADC 304.

  The orthogonal coordinate conversion unit 307 is a signal processing circuit that receives the amplitude data output from the integrator 305 and the phase data output from the integrator 306, and converts the polar coordinates to the orthogonal coordinates. The DAC 308 D / A converts the conversion data of the amplitude data output from the orthogonal coordinate conversion unit 307. The DAC 309 performs D / A conversion on the conversion data of the phase data output from the orthogonal coordinate conversion unit 307.

  Further, as described above, the amplitude comparator 301 to the DAC 309 compare the amplitude and phase of the cancellation signal generated by the quadrature modulator 202 and the received signal, and output a signal corresponding to the comparison result. 300 is configured. Furthermore, the cancellation signal switch 211 is a switch that is provided between the distributor 203 and the combiner 205, and makes the output of the distributor 203 and the input of the combiner 205 conductive or disconnected.

Next, the operation will be described.
First, a part of the transmission signal (carrier wave) extracted by the coupler 201 is input to the LO (local) terminal of the quadrature modulator 202. The quadrature modulator 202 uses the I and Q signals output from the DACs 308 and 309 to adjust the amplitude and phase of the signal extracted by the coupler 201 and outputs a cancellation signal. This canceling signal is distributed in reverse phase by the distributor 203, and the canceling signal output in reverse phase is combined with the received signal by the combiner 205 to cancel the leakage signal contained in the received signal.

  On the other hand, a part of the received signal before being combined with the cancellation signal by the combiner 205 is taken out by the distributor 204. The cancellation signal output from distributor 203 and the received signal output from distributor 204 are input to amplitude comparator 301 and phase comparator 302. The amplitude comparator 301 and the phase comparator 302 compare the amplitude and phase of the cancellation signal distributed by the distributor 203 and the received signal distributed by the distributor 205, and output a signal proportional to the amplitude difference and the phase difference. .

  The ADCs 303 and 304 A / D convert the amplitude difference signal and the phase difference signal output from the amplitude comparator 301 and the phase comparator 302, respectively. Further, the integrators 305 and 306 integrate the amplitude difference signal and the phase difference signal output from the ADCs 303 and 304, respectively, to obtain amplitude data and phase data.

  The orthogonal coordinate conversion unit 307 receives the amplitude data output from the integrator 305 and the phase data output from the integrator 306, and performs conversion from polar coordinates to orthogonal coordinates. The DACs 308 and 309 D / A convert each output from the orthogonal coordinate conversion unit 307. This signal is input to the quadrature modulator 202 as I and Q signals.

  For example, when the received signal taken out by the distributor 204 has a larger (smaller) amplitude than the cancellation signal distributed by the distributor 203, the amplitude comparator 301 outputs a positive (negative) signal proportional to the amplitude difference. As a result, the amplitude data output from the integrator 305 increases (decreases). Then, the amplitude of the I and Q signals (outputs of the DACs 308 and 309) obtained by D / A conversion of the result of converting the amplitude data and the phase data into the orthogonal coordinates by the orthogonal coordinate conversion unit 307 increases (decreases), and the orthogonal modulator 202 However, the amplitude of the cancellation signal generated by quadrature modulation of the I and Q signals also increases (decreases). Such control is always performed so that the amplitudes of the received signal and the cancellation signal are equal.

  On the other hand, when the phase of the received signal extracted by the distributor 204 is advanced (delayed) as compared with the cancellation signal distributed by the distributor 203, the phase comparator 302 also determines the phase difference. Since a proportional positive (negative) signal is output, the phase data output from the integrator 306 increases (decreases). Then, the phase of the I and Q signals (outputs of the DACs 308 and 309) obtained by D / A conversion of the result obtained by converting the amplitude data and the phase data into the orthogonal coordinates by the orthogonal coordinate conversion unit 307 advances (delays). However, the phase of the cancellation signal generated by quadrature modulation of the I and Q signals advances (delays). Such control is always performed so that the phase of the received signal and the cancellation signal are equal.

  In this way, the cancellation signal distributed by the distributor 203 is controlled so that the amplitude and phase are equal to the received signal extracted by the distributor 204. This canceling signal is distributed in reverse phase by the distributor 203 and is combined with the received signal by the combiner 205 via the canceling signal switch 211, so that the leakage signal contained in the received signal is canceled.

  The interrogator specifies in advance whether the response signal is a baseband modulation signal or a subcarrier signal. In the cancellation signal switch 211, a control unit (not shown) controls the response signal to be turned off when the response signal is a subcarrier modulation signal, and blocks the input of the cancellation signal to the combiner 205. As a result, instead of canceling out the leakage signal, thermal noise generated from the quadrature modulator, vector modulator, level adjustment amplifier, or the like in the circuit that generates the cancellation signal enters the receiving unit 108 via the synthesizer 205. To prevent.

  In the above description, feedback control is performed so that the cancellation signal has the same amplitude and phase as the leakage signal, but feedback control is performed so that the negative phase cancellation signal has the same amplitude and phase as the leakage signal. Alternatively, the anti-phase canceling signal may be generated by a quadrature modulator, and the received signal and the anti-phase combined signal may be combined in phase to cancel the leakage signal.

  That is, as a configuration in this case, the quadrature modulator 202 generates an anti-phase cancellation signal, and the signal comparison unit 300 compares the amplitude and phase of the anti-phase cancellation signal generated by the quadrature modulator 202 and the received signal. Then, a signal corresponding to the comparison result is output. Then, the quadrature modulator 202 and the signal comparison unit 300 perform feedback control so that the anti-phase canceling signal has the same amplitude and anti-phase as the leakage signal. In this case, the synthesizer 205 uses an in-phase distributor instead of the anti-phase distributor as the distributor 203 in order to synthesize the anti-phase cancellation signal output from the quadrature modulator 202 and the received signal in phase.

  In the example illustrated in FIG. 1, the transceiver includes the amplitude comparator 301 that compares the amplitudes of the cancellation signal and the reception signal and the phase comparator 302 that compares the phases of the cancellation signal and the reception signal. The present invention is not limited to this configuration. For example, you may apply to the transmitter / receiver of the following structures.

  FIG. 2 is a diagram illustrating another configuration example of the transceiver including the leakage signal cancellation circuit according to the first embodiment. 2 includes a transmitter 101, a local oscillator 102, a mixer 103, a power amplifier 104, a circulator 105, a quadrature demodulator 113, high-pass filters (HPF) 114 and 115, a receiver 116, a coupler 201, and a quadrature. A modulator 202, a combiner 205, a cancellation signal switch 211, A / D converters (ADC) 303 and 304, integrators 305 and 306, and D / A converters (DACs) 308 and 309 are provided.

  The quadrature demodulator 113 receives a part of the transmission signal (carrier wave) extracted by the coupler 201 and the output signal from the combiner 205, and demodulates the in-phase component signal and the quadrature component signal. HPFs 114 and 115 are filters for removing a DC component from the output signal of quadrature demodulator 113. In FIG. 2, the same components as those in FIG.

Next, the operation will be described.
First, part of the transmission signal (carrier wave) extracted by the coupler 201 is input to each LO (local) terminal of the quadrature demodulator 113 and the quadrature modulator 202. The quadrature modulator 202 uses the I and Q signals output from the DACs 308 and 309 to adjust the amplitude and phase of the signal extracted by the coupler 201 and outputs a cancellation signal. This canceling signal is combined with the received signal by the combiner 205, and the leakage signal included in the received signal is canceled.

  On the other hand, the quadrature demodulator 113 receives a part of the transmission signal (carrier wave) extracted by the coupler 201 and the output signal from the synthesizer 205, and demodulates in-phase component and quadrature component signals. In-phase and quadrature component signals output from the quadrature demodulator 113 are input to the ADCs 303 and 304 and the HPFs 114 and 115, respectively.

  The ADCs 303 and 304 A / D convert the in-phase component signal and the quadrature component signal input from the quadrature demodulator 113, respectively. Further, the integrators 305 and 306 integrate the signals output from the ADCs 303 and 304. The DACs 308 and 309 D / A convert each output from the integrators 305 and 306. This signal is input to the quadrature modulator 202 as I and Q signals.

  For example, when the in-phase component of the received signal is larger (smaller) than the in-phase component of the cancellation signal output from the quadrature modulator 202, the quadrature demodulator 113 outputs a positive (negative) signal proportional to the amplitude difference. Therefore, the amplitude of the in-phase component output from the integrator 305 increases (decreases). Then, the amplitude of the in-phase component of the cancellation signal generated by the quadrature modulator 202 by quadrature modulating the I and Q signals also increases (decreases). Similar control is performed on the orthogonal component. As a result, the reception signal and the cancellation signal are always controlled so that the in-phase component and the quadrature component are equal. That is, control is always performed so that the amplitude and phase of the received signal and the cancellation signal are equal.

  Also in this configuration, as in the case of FIG. 1, the interrogator specifies in advance whether the response signal is a baseband modulated signal or a subcarrier signal to the responder. In the cancellation signal switch 211, a control unit (not shown) controls the response signal to be turned off when the response signal is a subcarrier modulation signal, and blocks the input of the cancellation signal to the combiner 205. As a result, instead of canceling out the leakage signal, thermal noise generated from the quadrature modulator, vector modulator, level adjustment amplifier, or the like in the circuit that generates the cancellation signal enters the receiving unit 116 via the synthesizer 205. To prevent.

  In addition, within the range which does not deviate from the meaning of this invention, it can apply other than the structure mentioned above, and can obtain the same effect.

  As described above, according to the first embodiment, the cancellation signal switch 211 for turning on / off the input of the cancellation signal to the combiner 205 is provided, and when the response signal is a subcarrier modulation signal, the cancellation signal switch 211 is turned off. Since it did in this way, in a radio | wireless identification system, the sensitivity degradation by the noise which generate | occur | produces in a leak signal cancellation circuit can be prevented. Thereby, it is possible to realize an interrogator with little interference with the response signal regardless of whether the response signal of the responder is a baseband modulation method or a subcarrier modulation method.

It is a figure which shows the structure of the transmitter / receiver provided with the leakage signal cancellation circuit by Embodiment 1 of this invention. It is a figure which shows the other structural example of the transmitter / receiver provided with the leakage signal cancellation circuit by Embodiment 1. FIG.

Explanation of symbols

  101 Transmitter, 102 Local oscillator, 103, 106 Mixer, 104 Power amplifier, 105 Circulator, 107, 114, 115 High-pass filter (HPF), 108, 116 Receiver, 113 Quadrature demodulator, 201 Coupler, 202 Quadrature modulation , 203/204 distributor, 205 synthesizer, 211 cancellation signal switch, 301 amplitude comparator, 302 phase comparator, 303, 304 A / D converter (ADC), 305, 306 integrator, 307 Cartesian coordinate converter , 308, 309 D / A converter (DAC), 300 signal comparison means, 311, 311 a digital section.

Claims (3)

In a leakage signal cancellation circuit that is provided in a transceiver having an interrogator and a responder, and cancels a leakage signal to a reception signal of a transmission signal,
A combiner that combines the cancellation signal and the received signal to cancel the leakage signal;
A leakage signal canceling circuit, comprising: a canceling signal switch for turning on / off an input of the canceling signal to the combiner in accordance with a modulation method of the response signal of the responder.   2. The leak according to claim 1, wherein the cancellation signal switch turns off the input of the cancellation signal to the combiner when the modulation method of the response signal designated from the interrogator to the responder is a subcarrier modulation method. Signal cancellation circuit.   A transceiver comprising the leakage signal canceling circuit according to claim 1.

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