JP5158052B2 - Wireless communication device - Google Patents

Description

  The present invention relates to a wireless communication apparatus.

  Currently, wireless communication apparatuses that perform wireless communication processing by transmitting a wireless signal to a wireless tag such as an RFID tag and receiving a response signal are provided. Various communication systems are used in this type of wireless communication device. For example, a non-modulated carrier is transmitted from a reader body to a wireless tag, and the wireless tag that has received the unmodulated carrier performs modulation processing. A method of transmitting a reflected wave (back scatter method) or the like is employed. This method has an advantage that low power consumption driving is possible without requiring a carrier generation source on the wireless tag side.

JP 2006-217427 A JP 2008-301064 A

  By the way, when the carrier transmission to the wireless tag and the reception of the reflected wave from the wireless tag are performed at the same time as in the backscatter method, there is a possibility that the sneak signal of the transmission wave is mixed in the reception circuit that receives the reflected wave. When such a sneak signal occurs, there is a problem that this sneak signal raises the reception level and saturates the signal amplitude.

  As a technique for solving such a problem, a wraparound canceller circuit (carrier canceller) as disclosed in Patent Documents 1 and 2 is provided. In this sneak canceller circuit, a signal having the same amplitude and opposite phase is generated with respect to a sneak signal sneaking from the transmitting circuit to the receiving circuit side, and a reception signal in which the sneak signal is suppressed is generated by synthesizing this signal. . This type of sneak canceller circuit compares the amplitude and phase of the sneak signal sneaking from the transmitter circuit to the receiver circuit side with the amplitude and phase of the carrier output from the transmitter circuit, and the amplitude and phase information obtained from the comparison result Is input to the integration circuit, the signal component from the tag included in the wraparound signal (the component of the signal returned by the load modulation method) is removed. As a result, the influence of the signal from the tag is eliminated, and a reverse phase signal based only on the wraparound carrier component can be generated.

However, in the case of the conventional sneak canceller circuit, the response time of the output signal may not be appropriate because the time constant of the integration circuit is constant.
That is, in this wraparound canceller circuit, since it is necessary to generate a reverse phase signal of only the wraparound carrier, it has a time constant sufficient to suppress the normal signal (signal returned by the load modulation method) superimposed on this wraparound carrier. It was necessary to secure a long time to suppress the wraparound. However, if the time constant of the integration circuit is ensured sufficiently long in this way, the response time in the wraparound canceller circuit becomes longer according to this time constant, so the time from the end of the transmission command to the reception start timing is extremely long. If it is small (when the tag response is set to 640 kbps in EPC-Global-GEN2, etc.), since the influence of the transmission processing period remains after the reception processing period as shown in FIG. In the initial stage, the sneak signal cannot be sufficiently suppressed, the receiver is saturated, and the reading accuracy of the tag is lowered. FIG. 5 is a waveform diagram showing the relationship between the input signal to the integration circuit and the output signal from the integration circuit when shifting from the transmission command period to the reception processing period in the conventional wraparound canceller circuit. An input signal to the integration circuit is shown, and an output signal from the integration circuit is shown in the lower stage.

  In Patent Document 2, a cancel operation (cancellation training) is performed at a time before a transmission command in which the time constant of the integration means can be sufficiently secured, and the result of integration processing in the cancel training is stored in a memory. Then, the stored integration result is used for transmission / reception performed later, so that the canceling operation time is shortened and it is possible to quickly shift to communication with a tag or the like when switching the use frequency. In addition to the storage means, since a circuit for setting the stored phase adjustment amount and amplitude adjustment amount is required, there is a problem that the circuit scale increases.

  The present invention has been made to solve the above-described problem. Even when the period from the end of the transmission command to the start of the reception process is short, the influence of the transmission process period is affected at the initial stage of the reception process period. It is an object of the present invention to provide a wireless communication apparatus including a sneak canceller circuit that can prevent sneak current and can sufficiently suppress a sneak signal with high accuracy even in an initial stage of a reception processing period.

In order to achieve the above object, the invention according to claim 1 is a transmission / reception shared antenna, a transmission circuit that transmits a carrier-modulated signal according to a transmission command to a communication destination via the transmission / reception shared antenna, and the transmission command. A signal that is returned from the communication destination in response to the load modulation method via the transmission / reception shared antenna, and is connected between the transmission / reception shared antenna and the reception circuit. A wireless communication device comprising a sneak canceller circuit that cancels a sneak signal that sneaks to the receiving circuit side,
When the wraparound canceller circuit transmits the carrier from the transmission circuit, distribution means for distributing the reception signal from the transmission / reception shared antenna to the reception circuit, and the carrier transmitted from the transmission circuit as a reference signal Amplitude / phase information output means for outputting amplitude / phase information based on the reference signal and the received signal distributed by the distribution means; and the amplitude / phase information output from the amplitude / phase information output means Is integrated with the load modulation method to remove the component of the signal returned, based on the reference signal and the amplitude / phase information output from the integration means. Cancel signal generating means for generating a cancel signal adjusted to the phase, and the cancel signal generated by the cancel signal generating means. By combining with the received signal, and a, a combining means for selectively taking out the signal returned by the load modulation method.
Then, the time constant of the integration means is set to a second time during the reception processing period for performing the reception processing from the communication destination, rather than the first time constant during the transmission processing period for transmitting the transmission command from the transmission circuit. A time constant switching means for switching so that the time constant is larger is provided.

  According to a second aspect of the present invention, in the wireless communication device according to the first aspect, the time constant switching unit is configured to perform the integration between the end of the transmission command from the transmission circuit and the start timing of the reception processing period. The time constant of the means is switched.

  According to a third aspect of the present invention, in the wireless communication device according to the first or second aspect, the integrating means is composed of an RC circuit, and the time constant switching means is a resistance value switching for switching a resistance value of the RC circuit. It has the means.

  According to a fourth aspect of the present invention, in the wireless communication apparatus according to the first or second aspect, the time constant switching unit includes a path switching unit that switches a short circuit path of the integrating unit.

In the invention of claim 1, in the wraparound canceller circuit, when transmitting the carrier from the transmission circuit, the distribution means for distributing the reception signal from the shared antenna to the reception circuit and the carrier transmitted from the transmission circuit as a reference signal The amplitude / phase information output means for outputting the amplitude / phase information based on the reference signal and the received signal distributed by the distributing means, and the amplitude / phase information output from the amplitude / phase information output means are integrated, Based on the integration means that removes the component of the signal returned by the load modulation method, the reference signal, and the amplitude / phase information output from the integration means, a cancellation signal adjusted to the opposite phase to the sneak signal is generated. Cancel signal generated by the load modulation method by combining the received signal with the cancel signal generated by the cancel signal generating unit Signal synthesizing means for selectively taking out provided that. In this way, it is possible to remove a component of a regular signal (a signal returned by a load modulation method) from a received signal, and to selectively extract a sneak signal and accurately generate a signal having a phase opposite to that of the sneak signal.
Furthermore, the time constant of the integrating means is the second time constant during the reception processing period for performing the reception processing from the communication destination, rather than the first time constant during the transmission processing period for transmitting the transmission command from the transmission circuit. Time constant switching means for switching to increase is provided. In this way, during the reception processing period, the time constant can be lengthened, and the regular signal (the signal returned by the load modulation method) can be satisfactorily removed from the received signal. On the other hand, since the time constant can be shortened during the transmission processing period, the responsiveness of the cancel signal can be improved. Therefore, it is possible to effectively prevent the signal corresponding to the transmission command from remaining until the reception processing period, and as a result, the sneak signal can be sufficiently suppressed with high accuracy even in the initial stage of the reception processing period.

  In the invention of claim 2, the time constant switching means switches the time constant of the integrating means between the end of the transmission command from the transmission circuit and the start timing of the reception processing period. In this way, since a short time constant can be reliably maintained until the transmission command is completed, the response of the transmission command can be more reliably eliminated until the reception processing period. By the time it starts, it can be changed to a long time constant suitable for the reception process.

  According to a third aspect of the present invention, the integrating means comprises an RC circuit, and the time constant switching means has resistance value switching means for switching the resistance value of the RC circuit. In this way, a configuration in which the time constant of the integrating means can be switched by control can be realized without using a complicated configuration.

  According to a fourth aspect of the present invention, the time constant switching means has path switching means for switching the short-circuit path of the integrating means. In this way, a configuration in which the time constant of the integrating means can be switched by control can be realized without using a complicated configuration.

FIG. 1 is a block diagram schematically illustrating an electrical configuration of a wireless communication apparatus according to the first embodiment of the present invention. FIG. 2 is a circuit diagram illustrating a filter circuit (integrating means) used in the wireless communication apparatus of FIG. FIG. 3 shows the relationship between the input signal to the filter circuit (integrating means) and the output signal from the filter circuit when shifting from the transmission processing period to the reception processing period in the wraparound canceller circuit of the wireless communication apparatus of FIG. FIG. FIG. 4 is a circuit diagram schematically showing a modification of the filter circuit. FIG. 5 is a waveform diagram showing the relationship between the input signal to the integrating means and the output signal from the integrating means when shifting from the transmission command period to the receiving processing period in the conventional wraparound canceller circuit.

[First embodiment]
Hereinafter, a first embodiment in which a wireless communication device of the present invention is embodied will be described with reference to the drawings.
(Overall configuration of wireless communication device)
First, the outline of the wireless communication apparatus according to the first embodiment will be described with reference to FIG. In the following, a case where the wireless communication apparatus according to the present invention is applied to a reader / writer that communicates with an RFID tag using a UHF band carrier will be described as a representative example.

  The reader / writer (wireless communication apparatus) 1 is mainly composed of a transmission circuit 2, a circulator 3, a transmission / reception antenna 4, a reception circuit 7, a control unit 50, and the like, and is a non-contact communication medium such as the RFID tag 5 shown in FIG. And non-contact communication.

  The control unit 50 is configured by a CPU, ROM, RAM, FPGA, or the like, and has a function of controlling various operations of the reader / writer 1 in accordance with operation signals given from a key operation unit (not shown). It has a function of executing processing for outputting data to the circuit 2, processing of data input from the receiving circuit 7, and the like. It also has a function of outputting a time constant switching signal (switching timing signal) to the switching circuits 30 and 40 described later.

  The transmission circuit 2 functions to transmit a carrier in the UHF band (for example, frequency 953 MHz) to the RFID tag 5 (wireless tag) via the transmission / reception shared antenna 4. For example, a known carrier oscillator , An encoder, a modulator, an amplifier, a transmitter filter, and the like. The transmission circuit 2 amplifies the carrier by, for example, ASK (Amplitude Shift Keying) modulation using a transmission command, and then transmits the carrier wave as a radio signal via the circulator 3 and the antenna 4.

  The circulator 3 has a function of preventing the high-frequency signal output from the transmission circuit 2 from flowing in the reverse direction, and outputs the high-frequency signal input from the transmission circuit 2 side to the transmission / reception shared antenna 4. The high-frequency signal input from the side is output to the receiving circuit 7 side.

  The transmission / reception shared antenna 4 is an antenna that is also used for signal transmission to the RFID tag 5 and signal reception from the RFID tag 5, and a high-frequency signal (transmission signal) output from the transmission circuit 2 via the circulator 3 is wirelessly transmitted. It transmits to the RFID tag 5 as a signal and functions to receive a response signal (radio signal) output from the RFID tag 5.

  The receiving circuit 7 functions to receive a response signal sent back from the RFID tag 5 by a load modulation method in response to a transmission command from the transmitting circuit 2 via the shared antenna 4. The reception circuit 7 receives a reception signal from the RFID tag 5 received by the shared transmission / reception antenna 4 (specifically, a composite signal obtained by synthesizing a response signal from the RFID tag 5 and a cancel signal from the wraparound canceller circuit 10). Is demodulated, and the demodulated signal is binarized and then decoded.

  In addition to the above elements, the reader / writer 1 according to the present embodiment is provided with a power supply system such as a battery and a power supply circuit, a display unit such as a liquid crystal display, and operation means such as various operation keys. In FIG. 1, these illustrations are omitted.

  The RFID tag 5 that performs non-contact communication with the reader / writer 1 receives the carrier transmitted from the reader / writer 1 to generate an operation power supply, and divides the clock extracted from the carrier to generate an operation clock. . When the transmitted command is demodulated, a response to the command is returned by load modulating the carrier.

(Wraparound canceller circuit)
As shown in FIG. 1, the reader / writer 1 includes a wraparound canceller circuit 10. The wraparound canceller circuit 10 is connected between the transmission / reception shared antenna 4 and the reception circuit 7 and functions to cancel a wraparound signal that wraps around from the transmission circuit 2 to the reception circuit 7 side. Are demultiplexed by the couplers (demultiplexers) 8 and 9 to generate a reverse phase signal of the carrier, and the reverse phase signal is combined with the received signal by the combiner 20 on the input side of the receiving circuit 7. Thus, the carrier component contained in the received signal is removed.

  The wraparound canceller circuit 10 includes a quadrature demodulator 11, a quadrature modulator 13, filter circuits 17 and 18, a phase initial correction circuit 15, an amplitude initial correction circuit 16, an amplifier 19, and the like.

As shown in FIG. 2, the quadrature demodulator 11 multiplies the transmission-side carrier {cos (2πfct)} captured via the coupler 8 and the received signal captured via the coupler 9 and outputs an I signal. Multiplying the mixer, the phase shifter that shifts the carrier on the transmission side by 90 degrees, the phase-shifted signal {sin (2πfct)} shifted by the phase shifter, and the received signal captured via the coupler 9 And a mixer for outputting a Q signal.
In the present embodiment, the coupler 9 corresponds to an example of a “distributing unit” and functions to distribute a reception signal from the transmission / reception shared antenna 4 to the reception circuit 7 when transmitting a carrier from the transmission circuit 2. .
The quadrature demodulator 11 corresponds to an example of “amplitude / phase information output means”, and uses a carrier transmitted from the transmission circuit 2 (specifically, the carrier distributed by the coupler 8) as a reference signal. It functions to output an I signal and a Q signal (amplitude / phase information) based on the reference signal and the received signal distributed by the coupler 9.

  The filter circuits 17 and 18 correspond to an example of “integrating means”, and integrate the I signal and Q signal (amplitude / phase information) output from the quadrature demodulator 11 (amplitude / phase information output means). It functions to remove the component of the signal returned by the load modulation method. Specifically, as shown in FIG. 2, the Q signal from the quadrature demodulator 11 is inputted to the filter circuit 17, and the filter circuit 17 uses the normal signal (load modulation method) from the Q signal. The component of the signal sent back in is removed. Further, the I signal from the quadrature demodulator 11 is input to the filter circuit 18, and the filter circuit 18 obtains a component of a normal signal (a signal returned by the load modulation method) from the I signal. It has been removed. Both the I signal and Q signal (amplitude / phase information) that have passed through the filter circuits 17 and 18 are input to the cancel signal generator 13.

  The cancel signal generation unit 13 corresponds to an example of a “cancel signal generation unit”, and functions to generate a cancel signal adjusted to have an opposite phase to the sneak signal that wraps around from the transmission circuit 2 to the reception circuit 7 side. Yes. This cancel signal generation unit 13 includes an orthogonal demodulator 13a, and uses filter (17, 18) as a reference with reference to amplitude and phase information of the carrier (reference signal) from the transmission circuit 2 obtained via the coupler 8. On the basis of the I signal and Q signal output via, the carrier of the wraparound component is reproduced at a frequency of 953 MHz and converted to an opposite phase.

  The “signal having the opposite phase of the wraparound component” generated and output by the cancel signal generator 13 is corrected by the amplitude initial correction circuit 16, amplified by the amplifier 19, and input to the combiner 20.

  The synthesizer 20 includes a reception signal (a signal obtained by superimposing a sneak signal from the transmission circuit 2 on a response signal from the RFID tag 5) from the transmission / reception shared antenna 4 side, an amplitude initial correction circuit 16 and an amplifier from the cancel signal generation unit 13. The signal output via 19 (the signal having the opposite phase of the wraparound component) is combined, and this combination removes the wraparound component from the received signal from the transmission / reception shared antenna 4 side.

  Note that the phase initial correction circuit 15 and the amplitude initial correction circuit 16 are respectively the initial components of the sneak signal included in the received signal and the cancel signal generated by the cancel signal generation unit 13 (a signal having a phase opposite to the sneak signal). This circuit corrects a typical phase difference and amplitude difference.

  In the present embodiment, the time constants of the filter circuits 17 and 18 can be switched. Specifically, as shown in FIG. 2, each of the filter circuits 17 and 18 configured as an integral filter is provided with switching circuits 30 and 40 for switching time constants by selecting a resistor to be short-circuited. 17 and 18 (integration means), the first time constant in the “transmission processing period” (see FIG. 3) in which the transmission command is transmitted from the transmission circuit 2, the RFID tag 5 (communication destination) Switching is performed so that the second time constant during the reception processing period (see FIG. 3) in which the reception processing is performed becomes larger.

  Specifically, a time constant switching signal (switching timing signal) is output from the control unit 50 to the switching circuits 30 and 40 between the end of the transmission command from the transmission circuit 2 and the start timing of the reception processing period. For example, in the switching circuit 30, which one of SW <b> 1 and SW <b> 2 is turned on is switched between the “transmission processing period” and the “reception processing period”. In the switching circuit 30, the resistors R1 and R2 are short-circuited by the ON operation of SW1 and SW2, respectively, and the time constant is changed by changing the combination of the short-circuits of these resistors R1 and R2. Yes.

  Further, the switching circuit 40 switches which of SW3 and SW4 is turned on in the “transmission processing period” and the “reception processing period”. In the switching circuit 40, the resistors R3 and R4 are short-circuited by the ON operation of SW3 and SW4, respectively, and the time constant is changed by changing the combination of the short-circuits of these resistors R3 and R4. Yes. Thus, in this embodiment, the time constant of each filter circuit 17 and 18 can be switched to a long state and a short state by control of the control part 50. FIG.

  In the present embodiment, the control unit 50 and the switching circuits 30 and 40 correspond to examples of “time constant switching unit” and “path switching unit”, and a function of switching each time constant of the filter circuits 17 and 18 (integrating unit). Specifically, the switching circuits 30 and 40 function to switch the short-circuit path of each of the resistors R1 to R4.

  In this embodiment, on the premise of such a configuration, since each of the filter circuits 17 and 18 is set to a short time constant (first time constant) during the “transmission processing period”, FIG. Thus, in the “transmission processing period”, the responsiveness of the output signals from the filter circuits 17 and 18 is improved, and an output signal following the transmission command is output. Therefore, the influence of the response to the transmission command does not remain after the start of the reception process as indicated by reference numeral Z in FIG. In addition, after the transmission command is finished and before the reception start timing (that is, before the start of the reception processing period), the time constants of the filter circuits 17 and 18 are longer than those in the “transmission processing period” ( Therefore, during the “reception processing period”, the Q signal output from the quadrature demodulator 11 and the component of the regular signal (signal returned by the load modulation method) from the I signal are displayed. As a result, it is easy to generate an antiphase signal with only a wraparound signal with high accuracy.

(Main effects of this embodiment)
In the present embodiment, in the wraparound canceller circuit 10, when transmitting a carrier from the transmission circuit 2, a coupler 9 (distribution means) that distributes a reception signal from the transmission / reception shared antenna 4 to the reception circuit 7 and transmission from the transmission circuit 2. A quadrature demodulator 11 (amplitude / phase information output means) that outputs amplitude / phase information based on the reference signal and the received signal distributed by the coupler 9, and the quadrature demodulator 11. Filter circuits 17 and 18 (integrating means) for integrating the I signal and Q signal (amplitude / phase information) output from the signal and removing the signal component returned by the load modulation method; the reference signal and the filter circuit 17; Based on the I signal and Q signal (amplitude / phase information) from 18, a cancel signal generator 13 (key) generates a cancel signal adjusted to the opposite phase to the sneak signal. Canceling signal generating means) and a combiner 20 (combining means) for selectively extracting a signal returned by the load modulation method by combining the cancel signal generated by the cancel signal generating unit 13 with the received signal. Is provided. In this way, it is possible to remove a component of a regular signal (a signal returned by a load modulation method) from a received signal, and to selectively extract a sneak signal and accurately generate a signal having a phase opposite to that of the sneak signal.
Further, the time constant of the filter circuits 17 and 18 (integrating means) is set to perform the reception process from the communication destination than the first time constant in the “transmission processing period” in which the transmission command is transmitted from the transmission circuit 2. “Time constant switching means” is provided for switching so that the second time constant during the “processing period” is larger. In this way, during the “reception processing period”, the time constant can be lengthened, and the regular signal (the signal returned by the load modulation method) can be satisfactorily removed from the received signal. On the other hand, since the time constant can be shortened during the “transmission processing period”, the responsiveness of the output signal can be improved. It is possible to effectively prevent the signal corresponding to the transmission command from remaining until the “reception processing period”, and consequently, the sneak signal can be sufficiently accurately and sufficiently suppressed in the initial stage of the “reception processing period”.

  The “time constant switching means” switches the time constants of the filter circuits 17 and 18 (integration means) between the end of the transmission command from the transmission circuit 2 and the start timing of the “reception processing period”. In this way, since a short time constant can be reliably maintained until the transmission command is completed, it is possible to more reliably eliminate the transmission command response from remaining until the “reception processing period”. By the time the period starts, it can be changed to a long time constant suitable for the reception process.

  The “time constant switching means” has “path switching means” for switching the short-circuit path of the filter circuits 17 and 18 (integrating means). In this way, a configuration in which the time constants of the filter circuits 17 and 18 can be switched by control can be realized without using a complicated configuration.

[Other Embodiments]
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  In the above embodiment, the UHF band carrier is exemplified as the carrier to be transmitted from the transmission circuit 2, but the present invention is not limited to this example, and a configuration for transmitting a carrier in another band may be used.

In the above embodiment, an example as shown in FIG. 2 is shown as an example of “integrating means” and “time constant switching means”, but the integration that can remove a specific component from the I signal and Q signal from the quadrature demodulator 11. If it is a circuit, it will not be restricted to the example of FIG. For example, the integrating means may be a passive RC filter as shown in FIG. 4 (a), a passive LC filter as shown in FIG. 4 (b), or an active RC filter as shown in FIG. 4 (c). Good. Note that the example of FIG. 4 is merely an outline, and it is needless to say that other circuit elements can be added.
When an integral filter constituted by an RC circuit as shown in FIGS. 4A and 4C is used instead of the filter circuits 17 and 18, the time constant can be changed by changing the resistance value of the RC circuit. . 4 (a) and 4 (c), the time constant can be switched by giving a signal for turning on the switches SW5 and SW6 from the control unit 50. In this case, the control unit 50 and the switches SW5 and 6 This corresponds to an example of “time constant switching means” and “resistance value switching means”. In this way, a configuration in which the time constant of the integrating means can be switched by control can be realized without using a complicated configuration. Further, the present invention is not limited to the configuration in which the resistance value is changed by a short circuit by the switch. In any case of FIGS. 4A to 4C, another time constant changing method (for example, a variable capacitor as shown in FIG. A method of changing the capacity, etc.) may be used.

1. Reader / writer (wireless communication device)
2 ... Transmission circuit 4 ... Transmission / reception antenna 5 ... RFID tag (destination)
7 ... Receiving circuit 9 ... Coupler (distribution means)
DESCRIPTION OF SYMBOLS 10 ... Round-off canceller circuit 11 ... Quadrature demodulator (amplitude and phase information output means)
13: Quadrature modulator (cancellation signal generating means)
17, 18 ... Filter circuit (integrating means)
20 ... Synthesizer (synthesizer)
30, 40... Switching circuit (time constant switching means, path switching means)
50. Control unit (time constant switching means, resistance value switching means, path switching means)

Claims (4)

A transmitting / receiving antenna,
A transmission circuit for transmitting a signal obtained by modulating a carrier according to a transmission command to a communication destination via the transmission / reception shared antenna;
A receiving circuit for receiving a signal returned by the load modulation method from the communication destination according to the transmission command via the shared antenna;
A sneak canceller circuit that is connected between the transmission / reception shared antenna and the receiving circuit and cancels a sneak signal that sneaks from the transmitting circuit to the receiving circuit;
A wireless communication device comprising:
The wraparound canceller circuit is:
When transmitting the carrier from the transmission circuit, distribution means for distributing a reception signal from the transmission / reception shared antenna to the reception circuit, and using the carrier transmitted from the transmission circuit as a reference signal, the reference signal and the distribution Amplitude / phase information output means for outputting amplitude / phase information based on the received signal distributed by the means;
Integrating the amplitude / phase information output from the amplitude / phase information output means, and integrating means for removing a signal component returned by the load modulation method;
Cancel signal generating means for generating a cancel signal adjusted to the same amplitude and opposite phase as the sneak signal based on the reference signal and the amplitude / phase information output from the integrating means;
Combining the cancellation signal generated by the cancellation signal generation unit with the reception signal, thereby selectively extracting a signal returned by the load modulation method, and
Furthermore, the time constant of the integration means is set to a second time during the reception processing period for performing the reception processing from the communication destination, rather than the first time constant during the transmission processing period for transmitting the transmission command from the transmission circuit. A wireless communication apparatus, characterized in that time constant switching means for switching so that the time constant is larger is provided.   The time constant switching unit switches the time constant of the integration unit between the end of the transmission command from the transmission circuit and the start timing of the reception processing period. Wireless communication device. The integrating means comprises an RC circuit,
The radio communication apparatus according to claim 1, wherein the time constant switching unit includes a resistance value switching unit that switches a resistance value of the RC circuit.   The wireless communication apparatus according to claim 1, wherein the time constant switching unit includes a path switching unit that switches a short-circuit path of the integrating unit.

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