Communication Equipment

Abstract

The present invention discloses a communication device, comprising a first generating unit, a second generating unit, a sharing unit, a synthesizing unit, a first and a second measuring unit, a first and a second control unit, and a third control unit. The first and the second measuring units measure the levels of self-interference signals respectively extracted from the output signal from the synthesizing unit in correlation with the first bandwidth or the second bandwidth wider than the first bandwidth. The first control unit sets the amount of change in the amplitude and phase of the second generating unit during a first time width so that the level measured by the first measuring unit decreases, and the second control unit sets the amount of change in the amplitude and phase of the second generating unit during a second time width shorter than the first time width according to the increase in the level measured by the second measuring unit. The third control unit sets the amount of change in the amplitude and phase of the second generating unit to the first control unit before starting to receive a response signal sent from the opposite device, and sets the amount of change in the amplitude and phase of the second generating unit to the second control unit during the reception of the response signal.

Description

[0001] This application claims priority to Japanese application No. JP2021-178511, filed on November 1, 2021, and citing the contents of the aforementioned application, the disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0002] An embodiment of the present invention relates to a communication device. Background Art

[0003] In a communication device that uses a common antenna for transmission and reception, a portion of the transmission signal may overlap with the reception signal and flow into the reception system. The transmission signal component overlapped with the reception signal becomes a self-interference signal, which may lead to a decrease in communication quality due to saturation of the reception system and an increase in noise.

[0004] Therefore, there is known a technique of generating a cancellation signal having a phase opposite to that of a self-interference signal from a transmission signal and using the cancellation signal to cancel the self-interference signal.

[0005] The prior art sets the gain and phase shift amount for generating a suitable cancellation signal before the start of communication. Thereafter, during the communication process, the self-jammer signal is offset by the cancellation signal generated by the gain and phase shift amount set before the start of communication. Such a process is called self-jammer cancellation, hereinafter referred to as SJC control.

[0006] However, during communication, the self-interference signal may change due to changes in the surrounding environment of the antenna. If the self-interference signal changes significantly, the remaining self-interference signal after cancellation may become larger.

[0007] Based on this situation, a technology that can reduce the influence of a self-interference signal even if the self-interference signal changes during communication is desired. Summary of the invention

[0008] In view of the above problems, the problem to be solved by the present invention is to provide a communication device which can reduce the influence of the self-interference signal even if the self-interference signal changes during the communication process.

[0009] In order to solve the above-mentioned problems, the communication device of an embodiment of the present invention includes a first generating unit, a common unit, a second generating unit, a synthesizing unit, a first measuring unit, a first control unit, a second measuring unit, a second control unit and a third control unit. The first generating unit generates a transmission signal for wireless transmission; the common unit inputs the transmission signal generated by the first generating unit from the input end and outputs it from the input-output end, and outputs the signal input from the input-output end from the output end; the second generating unit changes the amplitude and phase of the transmission signal generated by the first generating unit to generate a cancellation signal; the synthesizing unit synthesizes the cancellation signal generated by the second generating unit with the signal output from the output end; the first measuring unit measures the level of the self-interference signal extracted from the output signal from the synthesizing unit in correlation with the first bandwidth; the first control unit sets the amount of change in the amplitude and phase of the second generating unit during a predetermined first time width so that the level measured by the first measuring unit is reduced. to a level that satisfies a preset condition; a second measuring unit that measures the level of a self-interference signal extracted from the output signal from the synthesizing unit in correlation with a second bandwidth wider than the first bandwidth; a second control unit that controls the amount of change in amplitude and phase of the second generating unit during a second time width shorter than the first time width based on an increase in the level measured by the second measuring unit so as to reduce the level measured by the second measuring unit; and a third control unit that causes the first control unit to set the amount of change in amplitude and phase of the second generating unit before starting to receive a response signal sent from the opposite device, and causes the second control unit to set the amount of change in amplitude and phase of the second generating unit during the process of receiving the response signal sent from the opposite device.

[0010] According to the above communication device, even if the self-interference signal varies during communication, the influence of the self-interference signal can be reduced.

[0011] In the above communication device, the first measurement unit includes a first filter that passes the signal component of the first bandwidth, and the second measurement unit includes a second filter that passes the signal component of the second bandwidth and has a higher response speed than the first filter.

[0012] According to the above-mentioned communication device, the time required for measurement can be varied.

[0013] In the above communication device, when the stability of the self-interference signal before starting to receive the response signal sent from the opposite device is low enough to meet a preset condition, the third control unit enables the control based on the second control unit in the subsequent reception.

[0014] According to the above communication device, by making the second control unit ineffective when the degree of stability is high, it is possible to reduce the processing load associated with the second control unit.

[0015] In the above-mentioned communication device, as the action mode of the communication device, there is a first communication mode and a second communication mode adapted to a communication distance shorter than the first communication mode, and the third control unit sets the first communication mode when starting to read, executes control based on the first control unit, and when setting the second communication mode, makes the control based on the second control unit effective.

[0016] According to the above communication device, it is possible to switch and utilize the communication mode in response to changes in the communication distance.

[0017] The above communication device further includes: a setting unit that sets the second communication mode when the stability of the self-interference signal before starting to receive the response signal sent from the opposite device is low enough to meet a preset condition.

[0018] According to the above communication device, the second communication mode can be set when the stability level is low.

[0019] In the above-mentioned communication device, the setting unit determines that the stability is low when the difference between the maximum value and the minimum value of the residual level of the cancellation signal is larger than the first threshold value, and sets the second communication mode, the cancellation signal is a signal based on the amplitude and phase set by the first control unit, and the third control unit executes the control of the second control unit in the second communication mode when the residual level of the cancellation signal measured by the second measuring unit is larger than the second threshold value.

[0020] According to the above communication device, it is possible to perform control of the second control unit according to the residual level in the second communication mode.

[0021] In the above communication device, in the first communication mode, the first control unit changes the amplitude and phase of the second generation unit, stops the change at a time point when a residual level value satisfying a preset condition is detected, and sets the amplitude and phase at that time point.

[0022] According to the above communication device, it is possible to shorten the time during which the amplitude and phase of the second generating unit change in the first communication mode.

[0023] In the above communication device, in the first communication mode, the first control unit changes the amplitude and phase of the second generation unit within the entire changeable range, and sets the amplitude and phase at a time point when the residual level is minimum.

[0024] According to the above communication device, the amplitude and phase at the time point when the residual level is minimum can be set by the first control unit.

[0025] In the above communication device, in the second communication mode, the second control unit changes the amplitude and phase of the second generation unit, stops the change at a time point when a residual level value satisfying a preset condition is detected, and sets the amplitude and phase at that time point.

[0026] According to the above communication device, it is possible to shorten the time during which the amplitude and phase of the second generating unit change in the second communication mode.

[0027] In the above-mentioned communication device, the second control unit changes the amplitude and phase of the second generation unit at a shorter time interval than that in the first communication mode.

[0028] According to the above communication device, it is possible to cope with the response speed related to the measurement of the residual level. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a block diagram showing the circuit structure of a main part of a reading device involved in one embodiment;

[0030] Figure 2 It means that the SJC process is controlled Figure 1 A block diagram of the configuration of the circuit constructed within the FPGA;

[0031] Figure 3 Yes means Figure 2 A diagram showing the frequency characteristics of the 1st LPF and the 2nd LPF in FIG.

[0032] Figure 4 is based on Figure 2 A flowchart of a control process of a control circuit in; and

[0033] Figure 5 It means Figure 2 A diagram showing an example of changes in the residual level measured by the measurement circuit in FIG.

[0034] Description of Reference Numerals

[0035] 10 Antenna 11 Oscillator 12 Phase shifter 13 DA converter

[0036] 14 Quadrature modulator 16 Power amplifier 18 Antenna duplexer

[0037] 19 Power line 20 Antenna 21 Vector modulator

[0038] 22 DA converter 23 Power combiner 24 Quadrature detector

[0039] 26 Baseband amplifier 27 AD converter 29 AD converter

[0040] 30 Control unit 301 CPU 302 FPGA 303 Memory

[0041] 3021 control circuit 3022 generation circuit 3023 conversion circuit

[0042] 3024, 3025 Selector 3028 Measurement circuit 3029 Detection circuit

[0043] 100 Reading device 200 RFID tag DETAILED DESCRIPTION

[0044] The following is an explanation of the embodiments using the accompanying drawings. In addition, the following is an explanation using a reading device for reading data stored in an RFID (radio frequency identification) tag as an example. The reading device is an example of a communication device that uses the RFID tag as a counterpart device for wireless communication when reading the above data.

[0045] Figure 1 1 is a block diagram showing the circuit configuration of the main parts of the reader 100 according to the present embodiment. The reader 100 includes an oscillator 11, a phase shifter 12, a DA (digital to analog) converter 13, an orthogonal modulator 14, a BPF (band-pass filter) 15, a power amplifier 16, an LPF (low-pass filter) 17, an antenna duplexer 18, a power supply line 19, an antenna 20, a vector modulator 21, a DA converter 22, a power synthesizer 23, an orthogonal detector 24, a BBP (base band filter) 25, a baseband amplifier 26, an AD (analog to digital) converter 27, an LPF 28, an AD converter 29, and a control unit 30. The control unit 30 includes a CPU 301, an FPGA (field programmable gate array) 302, and a memory 303. The antenna 20 may not be included in the reader 100, and any antenna may be connected to the feed line 19. The antenna 20 and the feed line 19 may not be included in the reader 100, and any feed line connected to any antenna may be connected to the antenna duplexer 18.

[0046] The oscillator 11 generates a sine wave having a preset frequency as a carrier wave.

[0047] The phase shifter 12 outputs a cosine wave as another carrier wave by shifting the phase of the carrier wave generated by the oscillator 11 by 90 degrees.

[0048] The DA converter 13 converts the transmission baseband signals of two channels outputted from the CPU 301 in a digital state into analog form.

[0049] The orthogonal modulator 14 inputs the transmission baseband signals of the two channels simulated by the DA converter 13 as modulated waves. The orthogonal modulator 14 inputs the carrier generated by the oscillator 11 and the carrier output from the phase shifter 12. Thereafter, the orthogonal modulator 14 obtains a transmission signal by orthogonal modulation using the modulation waves of the two channels and the carriers of the two channels.

[0050] The BPF 15 removes low-frequency components and high-frequency components from the transmission signal obtained by the orthogonal modulator 14 for band limiting.

[0051] The power amplifier 16 amplifies the power of the transmission signal that has passed through the BPF 15 to a level suitable for wireless transmission.

[0052] The LPF 17 removes high-frequency components from the transmission signal amplified by the power amplifier 16 .

[0053] The transmission signal is converted into a signal for wireless transmission by the processing in the BPF 15, the power amplifier 16 and the LPF 17. That is, the BPF 15, the power amplifier 16 and the LPF 17 constitute a first generation unit for generating a transmission signal for wireless transmission.

[0054] The antenna duplexer 18 includes an input terminal TI, an input / output terminal TIO, an output terminal TOA, and an output terminal TOB. The transmission signal that has passed through the LPF 17 is input to the input terminal TI. The antenna duplexer 18 outputs the transmission signal input to the input terminal TI from the input / output terminal TIO and the output terminal TOB. The antenna duplexer 18 outputs the signal input to the input / output terminal TIO from the output terminal TOA. Although the signal output from the output terminal TOA of the antenna duplexer 18 is a signal synthesized by the reception signal generated at the antenna 20 and the self-interference signal described later, the signal is only referred to as the reception signal below. The antenna duplexer 18 is an example of a common unit.

[0055] The power supply line 19 supplies a transmission signal output from the input / output terminal TIO of the antenna duplexer 18 to the antenna 20. The power supply line 19 transmits a reception signal generated by the antenna 20 to the input / output terminal TIO of the antenna duplexer 18.

[0056] The antenna 20 radiates a radio wave corresponding to a transmission signal supplied through the power supply line 19. The antenna 20 generates an electric signal corresponding to the transmitted radio wave as a reception signal.

[0057] The vector modulator 21 modulates the transmission signal output from the output terminal TOB of the antenna duplexer 18 to a signal having an amplitude and a gain corresponding to a vector represented by the control signals (hereinafter referred to as the I control signal and the Q control signal) of two channels provided from the DA converter 22. Hereinafter, the transmission signal modulated by the vector modulator 21 is referred to as a cancellation signal. That is, the vector modulator 21 is a functional unit that changes the amplitude and phase of the transmission signal to generate the cancellation signal, and corresponds to the second generation unit.

[0058] The DA converter 22 converts two control signals, namely, an I control signal and a Q control signal outputted from the control unit 30 in a digital state into analog signals, and obtains the I control signal and the Q control signal to be supplied to the vector modulator 21 .

[0059] The power combiner 23 combines the power of the cancellation signal output from the vector modulator 21 with the reception signal output from the output terminal TOA of the antenna duplexer 18. Thus, the power combiner 23 reduces the self-interference signal included in the reception signal. The power combiner 23 is an example of a combining unit.

[0060] The quadrature detector 24 performs quadrature detection on the received signal output from the power combiner 23 using two carriers output from the oscillator 11 and the phase shifter 12. The quadrature detector 24 outputs two channels of analog received baseband signals obtained by the quadrature detection in parallel. That is, the quadrature detector 24 is an example of a detection unit.

[0061] The BPF 25 extracts predetermined baseband components from the reception baseband signals of the two channels outputted from the quadrature detector 24. The passband of the BPF 25 includes a frequency band including the response signal from the RFID tag 200.

[0062] The baseband amplifier 26 amplifies the reception baseband signals of the two channels that have passed through the BPF 25 to levels suitable for digitization by the AD converter 27 .

[0063] The AD converter 27 digitizes the reception baseband signals of the two channels amplified by the baseband amplifier 26 .

[0064] LPF28 extracts a low frequency band corresponding to the self-interference signal component contained in each of the two-channel received baseband signals output from the orthogonal detector 25. The signal extracted by LPF28 contains the self-interference signal component remaining in the output of the power combiner 23. Therefore, the two-channel signals extracted by LPF28 are referred to as I residual signal and Q residual signal hereinafter.

[0065] The AD converter 29 digitizes the I residual signal and the Q residual signal output from the LPF 28 .

[0066] The CPU 301 outputs two-channel transmission baseband signals at a preset timing when communicating with the RFID tag 200 . The CPU 301 reconstructs data transmitted from the RFID tag 200 based on the two-channel reception signals digitized by the AD converter 27 .

[0067] FPGA 302 executes pre-programmed signal processing to perform various calculations accompanying information processing by CPU 311 at high speed. One of the functions of FPGA 302 includes a function of controlling vector modulator 21 based on the I residual signal and Q residual signal digitized by AD converter 29.

[0068] The memory 303 stores an information processing program describing information processing executed by the CPU 301. The memory 303 stores various data required by the CPU 301 when executing various information processing. The memory 303 stores various data generated or acquired when the CPU 301 executes various information processing.

[0069] Figure 2 This is a block diagram showing the configuration of a circuit constructed in FPGA 302 to control the SJC process.

[0070] like Figure 2 As shown, the circuit constructed in FPGA302 includes a control circuit 3021, a generation circuit 3022, a conversion circuit 3023, selectors 3024 and 3025, a first LPF 3026, a second LPF 3027, a measurement circuit 3028, and a detection circuit 3029.

[0071] When the control circuit 3021 receives the start signal for instructing the execution of the SJC process from the CPU 301, it executes the process described later (hereinafter referred to as the control process) for realizing the SJC process. Thereafter, the control circuit 3021 instructs the generation circuit 3022 to start scanning in the control process. In addition, the control circuit 3021 controls the selectors 3024 and 3025 in the control process. In addition, the control circuit 3021 sets the amplitude and phase of the cancel signal according to the amplitude minimum point detected by the detection circuit 3029 in the control process. Thereafter, the control circuit 3021 outputs a status signal for notifying the CPU 301 of the execution state of the SJC process.

[0072] The generating circuit 3022 generates a phase signal and an amplitude signal in a digital state, which respectively represent the amplitude and the phase of the cancellation signal. The generating circuit 3022 changes the phase signal and the amplitude signal sequentially during the scanning period to scan (sweep) the amplitude and the phase. The generating circuit 3022 fixes the phase signal and the amplitude signal during the period other than the scanning period so that the amplitude and the phase are constant.

[0073] The conversion circuit 3023 converts the phase signal and the amplitude signal obtained from the generation circuit 3022 into an I control signal and a Q control signal, which represent vectors corresponding to the phase and amplitude represented by the phase signal and the amplitude signal in a digital state. The I control signal and the Q control signal obtained by the conversion circuit 3023 are provided to the DA converter 22.

[0074] The selectors 3024 and 3025 select and enable one of the first LPF 3026 and the second LPF 3027 when the control circuit 3021 controls them. Then, the selector 3024 supplies the I residual signal and the Q residual signal output from the AD converter 29 to the enabled side of the first LPF 3026 and the second LPF 3027. The selector 3025 supplies the I residual signal and the Q residual signal that have passed through the enabled side of the first LPF 3026 and the second LPF 3027 to the measurement circuit 3028.

[0075] Either the first LPF 3026 or the second LPF 3027 allows the low-frequency components of each of the I residual signal and the Q residual signal to pass through. Thus, the first LPF 3026 and the second LPF 3027 attenuate the unwanted signal that reduces the measurement accuracy in the measurement circuit 3028. The characteristics of the first LPF 3026 and the second LPF 3027 can also be appropriately set by, for example, the designer of the reading device 100. However, the cutoff frequency of the first LPF 3026 is set smaller than the cutoff frequency of the second LPF 3027. That is, the bandwidth of the second LPF 3027 is wider than that of the first LPF 3026. Thus, the ability of the first LPF 3026 to attenuate the unwanted signal components is higher than that of the second LPF 3027. In addition, as the first LPF 3026 and the second LPF 3027, for example, a FIR (finite impulse response) filter can be used.

[0076] The first LPF 3026 is an example of a first filter, and the second LPF 3027 is an example of a second filter.

[0077] Figure 3 It is a diagram showing the frequency characteristics of the first LPF 3026 and the second LPF 3027.

[0078] like Figure 3 As shown in FIG. 1 , the cutoff frequency of the first LPF 3026 is smaller than the cutoff frequency of the second LPF 3027. In addition, the order of the first LPF 3026 is greater than that of the second LPF 3027. Figure 3 As shown, the gradient of the attenuation amount of the first LPF 3026 is larger than the gradient of the attenuation amount of the second LPF 3027.

[0079] The measurement circuit 3028 measures the amplitude of the residual signal (hereinafter referred to as a residual level) based on the I residual signal and the Q residual signal supplied from the selector 3025 .

[0080] The detection circuit 3029 detects the timing (hereinafter referred to as the amplitude minimum point) at which the residual level measured by the measurement circuit 3028 is minimum. Then, the detection circuit 3029 notifies the control circuit 3021 of the detected amplitude minimum point.

[0081] Next, the operation of the reading device 100 constructed as described above will be described. In addition, the operation for reading the RFID tag 200 may be, for example, other known operations using an orthogonal modulation method as a modulation method for wireless communication. Therefore, the description of the operation is omitted here, and the operation related to the SJC processing will be described.

[0082] Before explaining the operation, the self-interference signal will be explained.

[0083] The antenna duplexer 18 is designed so that the transmission signal input to the input terminal TI will not be output from the output terminal TOA. However, in the actual circuit configuration, it is difficult to completely prevent the transmission signal input to the input terminal TI from leaking from the output terminal TOA. Therefore, a part of the transmission signal input to the input terminal TI is directly output from the output terminal TOA. In addition, a part of the transmission signal output from the input and output terminal TIO of the antenna duplexer 18 is reflected at the feed point of the antenna 20 and transmitted to the antenna duplexer 18 through the power supply line 19. Such a reflected signal is output from the output terminal TOA according to the function of the antenna duplexer 18. Therefore, the signal output from the output terminal TOA of the antenna duplexer 18 contains a component of the transmission signal that is not output from the input and output terminal TIO but leaked out and a component of the transmission signal that is input to the input and output terminal TIO as a reflected signal. The signal after the components of such a transmission signal are synthesized is used as a self-interference signal. In addition, the characteristics of the antenna 20 reflecting the transmission signal at the feed point vary according to the environment around the antenna 20, such as the situation where the RFID tag 200 and other objects are close to the antenna 20. Therefore, the amplitude and phase of the signal reflected at the feed point of the antenna 20 also vary depending on the environment around the antenna 20. Under this influence, the amplitude and phase of the self-interference signal also vary depending on the environment around the antenna 20.

[0084] The environment around the antenna 20 is mainly affected by the object on which the RFID tag 200 is attached. In addition, the environment around the antenna 20 is affected by the table or the like on which the object on which the RFID tag 200 is attached is placed. Therefore, the smaller the distance between the antenna 20 and the RFID tag 200, that is, the smaller the communication distance, the lower the stability of the environment around the antenna 20 tends to be.

[0085] In addition, the self-interference signal is a signal from the transmission signal. Therefore, by changing the amplitude and phase of the signal branched from the transmission signal, a signal with the same frequency and amplitude as the self-interference signal but opposite phase can be generated. Thereafter, by synthesizing this signal with the received signal output from the output terminal TOA of the antenna duplexer 18, the self-interference signal contained in the received signal can be offset. In the reading device 100, the cancellation signal obtained by changing the amplitude and phase with the vector modulator 21 is synthesized with the received signal output from the output terminal TOA of the antenna duplexer 18 in the power synthesizer 23, thereby seeking to reduce the self-interference signal contained in the received signal.

[0086] In addition, the reading device 100 is used to read data from the RFID tag 200 attached to the article placed at a predetermined position in the warehouse, for example. Therefore, when a staff member holding the reading device 100 moves in front of a certain shelf, the reading device 100 reads the RFID tag 200 attached to the article placed on the shelf. As one working state at this time, there is a state in which the RFID tag 200 located in a relatively wide range is read by the staff member facing the shelf and aligning the reading device 100. In addition, as another working state, there is a state in which the adjacent RFID tag 200 is read by the staff member approaching the RFID tag 200 placed on the shelf and aligning the reading device 100. In the former working state, the communication distance between the reading device 100 and the RFID tag 200 becomes larger than that in the latter working state. Therefore, the operation mode of the reading device 100 suitable for a larger communication distance in the former working state is called a "long-distance mode". In addition, the operation mode of the reading device 100 suitable for a smaller communication distance in the latter working state is called a "short-distance mode". The long-distance mode is equivalent to the first communication mode, and the short-distance mode is equivalent to the second communication mode.

[0087] When the reading of the RFID tag 200 is to be started, the CPU 301 starts to output a transmission baseband signal set in advance, such as a non-modulated carrier wave, from the antenna 20. In addition, the CPU 301 starts to supply a start signal to the control circuit 3021.

[0088] When receiving the start signal, the control circuit 3021 starts the control process for the SJC process.

[0089] Figure 4 It is a flowchart of the control process.

[0090] As ACT1, the control circuit 3021 indicates that the state signal is in the "scanning" state.

[0091] As ACT 2 , the control circuit 3021 sets the long distance mode. At this time, the control circuit 3021 causes the selectors 3024 and 3025 to select the first LPF 3026 , for example.

[0092] As ACT3, the control circuit 3021 starts full-range scanning. For example, the control circuit 3021 instructs the generation circuit 3022 to start scanning. The generation circuit 3022 starts to generate and output the amplitude signal and the phase signal according to the instruction. After that, the generation circuit 3022 changes the state of the amplitude signal and the phase signal in sequence so that the amplitude and the phase represented by the amplitude signal and the phase signal change in sequence within the entire range of the changeable range of the amplitude and the phase in the vector modulator 21. As a result, the gain and the phase of the cancellation signal generated by the vector modulator 21 change in sequence. The period from when the generation circuit 3022 starts outputting the amplitude signal and the phase signal to when the change within the entire range of the changeable range of the amplitude and the phase ends is the scanning period for performing the full-range scanning.

[0093] During the scanning period, the amount of reduction of the self-interference signal changes sequentially by synthesizing the cancellation signal with the power synthesizer 23. Therefore, the I residual signal and the Q residual signal extracted by the LPF28 also change sequentially. The I residual signal and the Q residual signal are input to the measuring circuit 3028 via the first LPF3026. The measuring circuit 3028 measures the residual level based on the I residual signal and the Q residual signal that change as described above. The detection circuit 3029 detects the amplitude minimum point (a level that meets the pre-set conditions) as the time when the residual level measured by the measuring circuit 3028 is the minimum during the scanning period. However, the amplitude minimum point is not necessarily the time when the residual level is the minimum in the strict sense, and it can also be the time when the residual level is a sufficiently low value close to the minimum value (a level that meets the pre-set conditions). The time when the residual level is the amplitude minimum point can be arbitrarily set by, for example, the designer of the reading device 100.

[0094] In order to detect the time when the residual level is the minimum, the amplitude and phase need to be changed over the entire range. However, when a sufficiently low value is detected, the change of the amplitude and phase may be terminated at the time when a sufficiently low value is detected. The scanning period can be shortened.

[0095] At this time, the level of the self-interference signal extracted by the first LPF 3026 as the first filter is measured by the measuring circuit 3028, and the first LPF 3026 and the measuring circuit 3028 constitute a first measuring unit.

[0096] As ACT 4, the control circuit 3021 sets the amplitude and phase of the operation state of the vector modulator 21 for reproducing the amplitude minimum point detected by the detection circuit 3029 to the amplitude and phase of the period outside the scanning period. Thereafter, the control circuit 3021 instructs the generation circuit 3022 to fix the amplitude and phase. In this way, the generation circuit 3022 fixes the amplitude signal and phase signal generated and output in the state representing the indicated amplitude and phase. Correspondingly, the vector modulator 21 is set to a state of generating a cancellation signal that can well offset the current self-interference signal in the surrounding environment. Through this process, the control circuit 3021 functions as a first control unit.

[0097] As ACT 5, the control circuit 3021 sets the state signal to a state indicating "canceling". In this way, the CPU 301 starts to output a transmission baseband signal, which is used to cause the antenna 20 to transmit radio waves in order to read the RFID tag 200 at a preset timing. The reading device is in communication. The control of the first control unit is executed before the reading of the RFID tag 200 starts.

[0098] As ACT 6, the control circuit 3021 confirms whether the surrounding environment is stable. The control circuit 3021, for example, calculates the stability of the residual level measured by the measuring circuit 3028 within a preset period, and confirms whether the surrounding environment is stable based on the magnitude of the stability. The stability can be calculated as the difference between the maximum value and the minimum value, for example. In this case, the smaller the numerical value of the stability, the more stable the surrounding environment (the higher the stability). Therefore, it is considered that the control circuit 3021 determines that it is stable (the higher the stability) when, for example, the stability is less than or equal to a preset first threshold. Thereafter, the control circuit 3021 determines that the surrounding environment is stable, and proceeds to ACT 7. In addition, the first threshold can also be appropriately set by, for example, a designer of the reading device 100.

[0099] ACT6 and ACT7 are executed, and the control circuit 3021 waits for receiving the completion of the reading.

[0100] When the reading of all the RFID tags 200 to be read is completed, the CPU 301 notifies the control circuit 3021 of the completion of the reading. For example, the CPU 301 notifies the control circuit 3021 of the completion of the reading by stopping the supply of the start signal to the control circuit 3021. In addition, in this case, the CPU 301 continues to supply the start signal that was started when the reading should be started as described above during the reading process. Thereafter, the control circuit 3021, for example, determines YES in ACT 7 in the state of being notified of the completion, and ends the control process.

[0101] On the other hand, when the value is not equal to or less than the first threshold value, for example, the control circuit 3021 determines that the surrounding environment is unstable (the degree of stability is low) and makes a NO determination in ACT 6 , and proceeds to ACT 8 .

[0102] As ACT 8 , the control circuit 3021 sets the short distance mode. At this time, the control circuit 3021 causes the selectors 3024 and 3025 to select the second LPF 3027 , for example.

[0103] Thus, by executing the processes of ACT 6 and ACT 8 , the control circuit 3021 functions as a setting unit.

[0104] As ACT 9, the control circuit 3021 checks whether the surrounding environment has changed. Thereafter, if the control circuit 3021 cannot check the corresponding situation, it determines as NO and proceeds to ACT 10.

[0105] As ACT 10, the control circuit 3021 confirms whether the reading has been completed. Thereafter, if the control circuit 3021 cannot confirm the corresponding situation, it determines as NO and returns to ACT 9.

[0106] Thus, as ACT9 and ACT10, the control circuit 3021 waits for occurrence of an environmental change or completion of reading.

[0107] At this time, since the operation of the vector modulator 21 is fixed, the residual level changes according to the change of the self-interference signal. Therefore, when the residual level is greater than or equal to a preset second threshold, the control circuit 3021 determines that the environment has changed and determines YES, and proceeds to ACT 11. In addition, the second threshold can also be appropriately set by, for example, the designer of the reading device 100.

[0108] As ACT 11, the control circuit 3021 starts full-range scanning in the same manner as ACT 3.

[0109] Furthermore, instead of performing full range scanning as in ACT 3, the change may be stopped at the time when a residual level value that meets a preset condition is detected, and the amplitude and phase at that time may be set.

[0110] The following description will be given by taking full range scanning as an example.

[0111] However, here, the close distance mode is set, and the second LPF 3027 is selected by the selectors 3024 and 3025. Since the cutoff frequency of the second LPF 3027 is larger than that of the first LPF 3026, the time constant is smaller than that of the first LPF 3026. That is, the response speed related to the measurement of the residual level during the full range scanning of ACT11 is higher than that during the full range scanning of ACT3. Therefore, the control circuit 3021 changes the amplitude and phase of the vector modulator 21 at a shorter time interval in ACT11 than in ACT3. The amplitude and phase of the cancellation signal are changed. In addition, the change interval of the amplitude and phase in each step of ACT3 and ACT11 is appropriately set by, for example, the designer of the reading device 100 in such a manner that the response speed of the first LPF 3026 and the second LPF 3027 can be considered and the residual level can be normally measured by the measuring circuit 3028.

[0112] At this time, the level of the self-interference signal extracted by the second LPF 3027 as the second filter is measured by the measuring circuit 3028, and the second LPF 3027 and the measuring circuit 3028 constitute a second measuring unit.

[0113] In addition, the cutoff frequency of the second LPF 3027 is higher than that of the first LPF 3026. Therefore, the SN ratio of the I residual signal and the Q residual signal supplied to the measuring circuit 3028 is larger when the full range is scanned in ACT11 than when the full range is scanned in ACT3. As a result, the error of the residual level measured by the measuring circuit 3028 is larger when the full range is scanned in ACT11 than when the full range is scanned in ACT3. That is, the error of the minimum amplitude point detected by the detection circuit 3029 is also larger when the full range is scanned in ACT11 than when the full range is scanned in ACT3.

[0114] As ACT 12, the control circuit 3021 sets the amplitude and phase of the vector modulator 21 in the same manner as ACT 4. Through this process, the control circuit 3021 functions as a second control unit.

[0115] Then, the control circuit 3021 returns to the state of waiting for ACT 9 and ACT 10. Thus, the control circuit 3021 repeats the full range scanning in ACT 11 and the setting of the amplitude and phase in ACT 12 every time the surrounding environment changes until the reading is completed. After that, the control circuit 3021 determines YES in ACT 10 when the CPU 301 notifies the completion, and ends the control process.

[0116] Figure 5 This is a diagram showing an example of changes in the residual level measured by the measurement circuit 3028.

[0117] like Figure 5 As shown, by the control of the vector modulator 21 based on ACT3 and AC4 (hereinafter referred to as initial control), the residual level is reduced to a sufficiently small value over a relatively long period of time.

[0118] exist Figure 5 In the example of FIG. 1 , after the initial control is completed, the residual level gradually increases according to the change of the surrounding environment. Thereafter, the control of the vector modulator 21 based on ACT11 and ACT12 (hereinafter referred to as the receiving control) is performed according to the situation that the residual level becomes greater than or equal to the second threshold. Through the receiving control, the residual level is reduced to less than the second threshold again. However, due to the influence of the detection error of the amplitude minimum point as described above, the residual level after the receiving control becomes larger than the residual level after the initial control.

[0119] As described above, the control circuit 3021 performs initial control based on the function of the first control unit before receiving (before communication starts), performs control during reception based on the function of the second control unit during reception (during communication), and functions as a third control unit. That is, the control of the first control unit is performed before reading of the RFID tag 200 starts. The control of the second control unit is performed during reading of the RFID tag 200.

[0120] By the above operation, the residual level is also monitored during reception in the reading device 100, and when the residual level increases, the receiving operation is continued and the vector modulator 21 is readjusted. Therefore, even if the self-interference signal changes during communication due to the influence of changes in the surrounding environment, the influence of the self-interference signal can be reduced.

[0121] In addition, the reading device 100 reduces the accuracy and performs the full range scanning controlled during reception in a short time. Therefore, it is possible to get rid of the state of large residual level in a short time, and reduce the influence of the self-interference signal.

[0122] In addition, the reading device 100 performs the receiving control only when the residual level after the initial control is completed is unstable. When the residual level after the initial control is completed is stable, it is considered that the object that causes the change in the surrounding environment is not close to the antenna 20. In this case, it can be considered that the change in the self-interference signal is small. Therefore, in this situation, by not performing the receiving control, the increase in the processing load associated with the receiving control can be suppressed.

[0123] In addition, the reader 100 switches between the long-distance mode using the first LPF 3026 suitable for a relatively large communication distance and the short-distance mode using the second LPF 3027 suitable for a relatively small communication distance, depending on the stability of the residual level after the initial control is completed. Thereafter, the reader 100 uses the long-distance mode in the initial control, and the control during reception is performed only in the short-distance mode. Thus, the operation states of the initial control and the control during reception can be switched by switching the operation mode adapted to the change in the communication distance.

[0124] This embodiment may also be variously modified as follows.

[0125] It is also possible to realize it as a communication device for communicating with the RFID tag 200 in order to write to the RFID tag 200. In addition, it is also possible to realize it as a communication device for communicating with a communication device different from the RFID tag 200.

[0126] When the residual level after the initial control is completed is stable, the control during reception can also be performed.

[0127] The cancel signal may be generated without using the vector modulator 21. For example, instead of the vector modulator 21, a variable attenuator and a variable phase shifter may be connected in series.

[0128] Instead of the selectors 3024 and 3025 , the first LPF 3026 , and the second LPF 3027 , an LPF whose cutoff frequency can be changed may be used.

[0129] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, changes, etc. can be made without departing from the scope of the gist of the invention. In addition, these embodiments and their variations are all included in the scope and gist of the invention, and are included in the invention described in the scope of the claims and their equivalents.

Claims

1. A communication device, characterized in that: include: A first generating unit, generating a transmission signal for wireless transmission; a common part that inputs the transmission signal generated by the first generation part from the input end and outputs it from the input-output end, and outputs the signal input from the input-output end from the output end; a second generating unit that generates a cancel signal by changing the amplitude and phase of the transmission signal generated by the first generating unit; a synthesizing unit that synthesizes the cancel signal generated by the second generating unit into the signal output from the output terminal; a first measuring unit for measuring a level of a self-interference signal extracted from an output signal from the synthesizing unit in correlation with a first bandwidth; a first control unit that sets the amount of change in the amplitude and phase of the second generating unit within a predetermined first time width so as to reduce the level measured by the first measuring unit to a level that satisfies a predetermined condition; a second measuring unit that measures a level of a self-interference signal extracted from an output signal from the synthesizing unit in correlation with a second bandwidth, the second bandwidth being wider than the first bandwidth; a second control unit that sets the amount of change in amplitude and phase in the second generating unit during a second time width shorter than the first time width so as to reduce the level measured by the second measuring unit in response to an increase in the level measured by the second measuring unit; as well as The third control unit causes the first control unit to set the amount of change in the amplitude and phase of the second generating unit before starting to receive the response signal sent from the opposite device, and causes the second control unit to set the amount of change in the amplitude and phase of the second generating unit during the process of receiving the response signal sent from the opposite device.

2. The communication device according to claim 1, wherein: The first measuring unit includes a first filter that passes a signal component of the first bandwidth, and the second measuring unit includes a second filter that passes a signal component of the second bandwidth and has a higher response speed than the first filter.

3. The communication device according to claim 1 or 2, wherein: The third control unit enables the setting by the second control unit in the subsequent reception when the stability level of the self-interference signal before starting to receive the response signal transmitted from the opposite device is low enough to meet a preset condition.

4. The communication device according to claim 1 or 2, wherein: The communication device has, as operation modes, a first communication mode and a second communication mode adapted to a communication distance shorter than the first communication mode, The third control unit sets the first communication mode when reading is started and executes control by the first control unit, and when setting the second communication mode, enables the setting by the second control unit.

5. The communication device according to claim 4, wherein: Also includes: The setting unit sets the second communication mode when the stability level of the self-interference signal before starting to receive the response signal transmitted from the opposite device is low enough to meet a preset condition.

6. The communication device according to claim 5, wherein: In the first communication mode, the first control unit changes the amplitude and phase of the second generation unit, stops the change at a time point when a residual level value satisfying a preset condition is detected, and sets the amplitude and phase at that time point.

7. The communication device according to claim 5, wherein: In the first communication mode, the first control unit changes the amplitude and phase of the second generation unit within the entire changeable range, and sets the amplitude and phase at a time point when the residual level is minimum.

8. The communication device according to claim 6, wherein: In the second communication mode, the second control unit changes the amplitude and phase of the second generation unit, stops the change at a time point when a residual level value satisfying a preset condition is detected, and sets the amplitude and phase at that time point.

9. The communication device according to claim 8, wherein: The second control unit changes the amplitude and phase of the second generator at a shorter time interval than that in the first communication mode.

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