communication equipment

Abstract

To shorten the time required to configure settings for generation of a cancellation signal.SOLUTION: A communication apparatus comprises first, second, and third generation units, a sharing unit, a synthesis unit, a detection unit, first and second controllers, and a selection unit. The first controller so controls the second generation unit as to generate a cancellation signal with the gain and phase shift amount corresponding to an error level detected by the detection unit. The third generation unit generates a plurality of prediction models associating the fluctuation pattern of an expected error level with the gain and phase shift amount on the basis of a plurality of record results of fluctuation patterns of the error level detected during a first period after the start of the fluctuation of the error level and the gain and phase shift amount determined after the convergence of the plurality of fluctuations. The selection unit selects one of the plurality of prediction models on the basis of the fluctuation pattern of the error level after the start of the fluctuation. The second controller so controls the second generation unit as to generate a cancellation signal with the gain and phase shift amount shown in the selected prediction model.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a communication device. [Background technology]

[0002] In communication devices that share an antenna for both transmission and reception, a portion of the transmission signal may be superimposed on the reception signal and enter the reception system. This superimposed transmission signal component may become a self-interference signal, which may cause saturation of the reception system and increase noise, resulting in a deterioration of communication quality. Therefore, a technique is known in which a cancellation signal having an opposite phase to the self-interference signal is generated from a transmission signal and used to cancel out the self-interference signal.

[0003] However, conventionally, the gain and phase shift amount for generating an appropriate cancellation signal are set by sweeping the phase shift amount and gain, which takes a long time. Under these circumstances, it has been desired to reduce the time required for setting up the generation of the cancellation signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-8313 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a communication device that can reduce the time required for setting up to generate a cancellation signal. [Means for solving the problem]

[0006] A communication device according to an embodiment includes a first generating unit, a duplexer, a second generating unit, a combining unit, a detecting unit, a first control unit, a third generating unit, a selecting unit, and a second controlling unit. The first generating unit generates a transmission signal for wireless transmission. The combining unit receives the transmission signal generated by the first generating unit from an input terminal and outputs it from an input / output terminal, and also outputs the signal input from the input / output terminal from an output terminal. The second generating unit generates a cancellation signal by changing the amplitude and phase of the transmission signal generated by the first generating unit. The combining unit combines the cancellation signal with the signal output from the output terminal. The detecting unit detects an error level between the cancellation signal and a self-interference signal included in the output signal from the output terminal. The first controlling unit controls the second generating unit to generate a cancellation signal with a gain and phase shift amount determined according to the error level detected by the detecting unit. The third generation unit records a fluctuation pattern of the error level detected by the detection unit multiple times during a predetermined first period after the error level detected by the detection unit starts to fluctuate, and generates multiple prediction models that associate a fluctuation pattern of the error level predicted for a second period that is an initial part of the first period with the gain and phase shift amount after the fluctuation convergence based on the gain and phase shift amount determined by the first control unit after the multiple times of the error level fluctuation convergence and the recorded fluctuation patterns. The selection unit selects one of the multiple prediction models generated by the third generation unit based on the fluctuation pattern detected by the detection unit during the second period after the error level detected by the detection unit starts to fluctuate. The second control unit controls the second generation unit to generate a cancellation signal with the gain and phase shift amount represented in the prediction model selected by the selection unit. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a block diagram showing the main circuit configuration of a reading device according to an embodiment. [Figure 2] 10 is a flowchart of a learning process. [Figure 3] 10A and 10B are diagrams showing examples of fluctuations in amplitude and phase of a self-interference signal; [Figure 4] 10A and 10B are diagrams showing examples of fluctuations in amplitude and phase of a self-interference signal; [Figure 5] 10A and 10B are diagrams showing examples of fluctuations in amplitude and phase of a self-interference signal; [Figure 6] 10 is a flowchart of a control process. [Figure 7] FIG. 10 is a diagram showing an example of a limited range. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the following, a reader that reads data stored in an RFID (radio frequency identification) tag will be described as an example. This reader communicates wirelessly with the RFID tag when reading the data, and is an example of a communication device.

[0009] FIG. 1 is a block diagram showing the main circuit configuration of a reading device 100 according to this embodiment. The reading device 100 includes an oscillator 11, a phase shifter 12, a digital-to-analog (DA) converter 13, a quadrature modulator 14, a band-pass filter (BPF) 15, a power amplifier 16, a low-pass filter (LPF) 17, an antenna duplexer 18, a feeder 19, an antenna 20, a variable attenuator 21, a variable phase shifter 22, a DA converter 23, a power combiner 24, a quadrature detector 25, a BPF 26, a baseband amplifier 27, an analog-to-digital (AD) converter 28, an LPF 29, an AD converter 30, and a control unit 31. The control unit 31 includes a CPU 311, a field programmable gate array (FPGA) 312, and a memory 313. The antenna 20, or the feeder 19 and the antenna 20, may not be included in the reading device 100, and any separate device may be connectable.

[0010] The oscillator 11 generates a sine wave of a predetermined frequency as a carrier wave. Phase shifter 12 shifts the phase of the carrier wave generated by oscillator 11 by 90 degrees, and outputs a cosine wave as another carrier wave.

[0011] The DA converter 13 converts the two systems of transmission baseband signals output in digital form from the CPU 311 into analog signals. Note that, hereinafter, the two systems of transmission baseband signals are referred to as I signals and Q signals, respectively.

[0012] The quadrature modulator 14 receives as modulated waves the I and Q signals converted to analog form by the DA converter 13. The quadrature modulator 14 receives as input the carrier wave generated by the oscillator 11 and the carrier wave output from the phase shifter 12 as I and Q system carrier waves, respectively. The quadrature modulator 14 then obtains a transmission signal by quadrature modulation.

[0013] The BPF 15 removes low-frequency components and high-frequency components from the transmission signal obtained by the quadrature modulator 14 in order to limit the band. 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. The LPF 17 removes harmonic components from the transmission signal amplified by the power amplifier 16 . The transmission signal becomes a signal for wireless transmission through the processes of BPF 15, power amplifier 16, and LPF 17. In other words, BPF 15, power amplifier 16, and LPF 17 form a first generation unit that generates a transmission signal for wireless transmission.

[0014] The antenna duplexer 18 has 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. The signal output from the output terminal TOA of the antenna duplexer 18 is a signal obtained by combining the received signal generated at the antenna 20 and a self-interference signal, which will be described later, and this signal will be simply referred to as the received signal below. The antenna duplexer 18 is an example of a duplexer.

[0015] The feeder line 19 supplies the transmission signal output from the input / output terminal TIO of the antenna duplexer to the antenna 20. The feeder line 19 transmits the reception signal generated at the antenna 20 to the input / output terminal TIO of the antenna duplexer . The antenna 20 emits radio waves corresponding to the transmission signal supplied by the power supply line 19. The antenna 20 generates an electric signal corresponding to the incoming radio waves as a reception signal.

[0016] The variable attenuator 21 attenuates the transmission signal output from the output terminal TOB of the antenna duplexer 18 with a gain according to the gain setting signal supplied from the DA converter 23 . The variable phase shifter 22 changes the phase of the transmission signal after attenuation by the variable attenuator 21 by an amount of phase shift according to a phase-shift amount setting signal supplied from the DA converter 23. The transmission signal after being phase-shifted by the variable phase shifter 22 is hereinafter referred to as a cancellation signal. Thus, the variable attenuator 21 and the variable phase shifter 22 realize the function of a second generating unit that generates a cancellation signal.

[0017] The DA converter 23 converts the gain setting data output from the control unit 31 into an analog gain setting signal and supplies it to the variable attenuator 21. The DA converter converts the phase shift amount setting data output from the control unit 31 into an analog phase shift amount setting signal and supplies it to the variable phase shifter 22.

[0018] The power combiner 24 combines the power of the received signal output from the output terminal TOA of the antenna duplexer 18 with the cancellation signal output from the variable phase shifter 22. In this way, the power combiner 24 reduces the self-interference signal included in the received signal. The power combiner 24 is an example of a combining unit.

[0019] The quadrature detector 25 performs quadrature detection on the received signal output from the power combiner 24 using two carrier waves output from the oscillator 11 and the phase shifter 12. The quadrature detector 25 outputs, in parallel, two systems of analog received baseband signals obtained by quadrature detection. In other words, the quadrature detector 25 is an example of a detection section.

[0020] The BPF 26 extracts components of a desired frequency band from each of the two systems of received baseband signals output from the quadrature detector 25 . The baseband amplifier 27 amplifies each of the two received baseband signals that have passed through the BPF 26 to a level suitable for digitization by the AD converter 28 . The AD converter 28 digitizes each of the two systems of received baseband signals amplified by the baseband amplifier 27 .

[0021] The LPF 29 removes harmonic components contained in each of the two systems of received baseband signals output from the quadrature detector 25 . The AD converter 30 digitizes each of the two systems of received baseband signals output from the LPF 29 .

[0022] When communicating with the RFID tag 200, the CPU 311 outputs an I signal and a Q signal according to a predetermined sequence. The CPU 311 reconstructs the data sent from the RFID tag 200 based on the two systems of received signals digitized by the AD converter 28. The CPU 311 executes information processing, which will be described later, for adjusting the gain of the variable attenuator 21 and the amount of phase shift in the variable phase shifter 22 based on the two systems of received baseband signals digitized by the AD converter 30.

[0023] The FPGA 312 performs pre-programmed signal processing to quickly execute various calculations associated with the information processing by the CPU 311. One of the functions of the FPGA 312 is to calculate the error level of the cancellation signal relative to the self-interference signal based on the levels of the two systems of received baseband signals digitized by the AD converter 30. Thus, the FPGA 312 functions as a detector that detects the error level by calculation based on the levels of the two systems of received baseband signals.

[0024] The memory 313 stores an information processing program that describes information processing to be executed by the CPU 311. The memory 313 stores various data required for the CPU 311 to execute various types of information processing. The memory 313 stores various types of data generated or acquired when the CPU 311 executes various types of information processing.

[0025] Next, the operation of the reader 100 configured as described above will be described. Note that the operation for reading the RFID tag 200 may be another known operation that uses, for example, quadrature modulation as a modulation method for wireless communication. Therefore, the description of that operation will be omitted here, and the operation for adjusting the gain of the variable attenuator 21 and the phase shift amount in the variable phase shifter 22 will be described.

[0026] Before describing the operation, a self-interference signal will be described. The antenna duplexer 18 is designed so that a transmit signal input to the input terminal TI is not output from the output terminal TOA. However, in an actual circuit configuration, it is difficult to completely prevent the transmit signal input to the input terminal TI from leaking out from the output terminal TOA. For this reason, a portion of the transmit signal input to the input terminal TI is output directly from the output terminal TOA. Furthermore, a portion of the transmit signal output from the input / 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 via the feed line 19. This reflected signal is output from the output terminal TOA by the function of the antenna duplexer 18. Thus, the signal output from the output terminal TOA of the antenna duplexer 18 includes a component of the transmit signal that leaks out without being output from the input / output terminal TIO and a component of the transmit signal that is input to the input / output terminal TIO as a reflected signal. The signal resulting from the combination of these transmit signal components is a self-interference signal. The reflection characteristics of the transmit signal at the feed point of the antenna 20 vary depending on the environment surrounding the antenna 20, such as the proximity of the RFID tag 200 and other objects 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. As a result, the amplitude and phase of the self-interference signal also vary depending on the environment around the antenna 20.

[0027] The self-interference signal is a signal derived from the transmission signal. Therefore, by changing the amplitude and phase of a signal branched from the transmission signal, it is possible to generate a signal having the same frequency and amplitude as the self-interference signal but an opposite phase. Then, by combining such a signal with the reception signal output from the output terminal TOA of the antenna duplexer 18, the self-interference signal contained in the reception signal can be canceled. In the reader 100, the cancellation signal obtained by changing the amplitude and phase using the variable attenuator 21 and the variable phase shifter 22 is combined with the reception signal output from the output terminal TOA of the antenna duplexer 18 using the power combiner 24, thereby reducing the self-interference signal contained in the reception signal.

[0028] The reader 100 is used, for example, to read data from RFID tags 200 attached to items placed at predetermined positions in a warehouse. For this reason, when a worker carrying the reader 100 moves to a shelf and repeatedly has the reader 100 read the RFID tags 200 attached to items placed on the shelf, the tendency of changes in the self-interference signal may be similar.

[0029] Therefore, the administrator or maintenance personnel of the reading device 100 performs work to have the reading device 100 learn the above-mentioned trends as an initial setting work before starting to use the reading device 100, or as a maintenance work in response to shelf layout changes, etc. At this time, the manager or maintenance personnel uses the reading device 100 operated in the learning mode to repeat operations simulating actual reading operations.

[0030] When the reading device 100 is set to the learning mode, the CPU 311 executes a learning process as information processing in accordance with an information processing program stored in the memory 313 . FIG. 2 is a flowchart of the learning process.

[0031] In ACT 1, the CPU 311 performs a full-range scan. For example, the CPU 311 checks the error level while gradually changing the gain and the phase shift amount over the entire adjustable range of the gain of the variable attenuator 21 and the entire adjustable range of the phase shift amount of the variable phase shifter 22, and finds the combination of gain and phase shift amount that minimizes the error level.

[0032] The error level is an index value of the magnitude of the error between the cancellation signal and the self-interference signal. The error level is determined by the FPGA 312 performing predetermined arithmetic processing on the two systems of digitally received baseband signals output from the AD converter 30. As an example, if the signal levels of the two systems of digitally received baseband signals are represented as LI and LQ, the FPGA 312 calculates the error level by SQR(LI 2 +LQ 2 ) where "SQR" represents the square root. However, the error level may be calculated by the CPU 311 through information processing.

[0033] In ACT2, the CPU 311 sets the gain and phase shift amount found in ACT1 in the variable attenuator 21 and the variable phase shifter 22. For example, the CPU 311 outputs gain setting data and phase shift amount setting data corresponding to the gain and phase shift amount found in ACT1 to the DA converter 23. The gain setting data and phase shift amount setting data are then converted into analog signals by the DA converter 23, and the resulting gain setting signals and phase shift amount setting signals are supplied to the variable attenuator 21 and the variable phase shifter 22. In response to this, the variable attenuator 21 and the variable phase shifter 22 perform attenuation and phase shift with the gain and phase shift amount found in ACT1, and enter a state where they generate cancellation signals.

[0034] 3, 4 and 5 are diagrams showing examples of fluctuations in amplitude and phase of a self-interference signal. 3 to 5, the amplitude and phase of the self-interference signal fluctuate due to environmental changes such as movement of the reader 100. Here, the CPU 311 does not change the gain and phase shift of the variable attenuator 21 and the variable phase shifter 22, so the error level fluctuates with the fluctuations in the amplitude and phase of the self-interference signal.

[0035] In ACT3, the CPU 311 waits for a variation to occur in the self-interference signal. Then, for example, when the error level becomes equal to or greater than a predetermined first threshold, the CPU 311 determines that a variation has occurred in the self-interference signal, determines YES, and proceeds to ACT4. The CPU 311 determines that a variation has occurred, for example, at time TAA in FIG. 3, time TBA in FIG. 4, or time TCA in FIG. 5. The first threshold may be arbitrarily determined by the designer of the reading device 100 or the creator of the information processing program.

[0036] In ACT 4, the CPU 311 starts sampling and recording the error levels. For example, the CPU 311 acquires the error levels from the FPGA 312 at predetermined time intervals and stores the acquired error levels so that the order of acquisition can be confirmed.

[0037] In ACT 5, the CPU 311 checks whether the fluctuation in the self-interference signal has converged. For example, if the amount of change in the error level per unit time is smaller than a predetermined second threshold, the CPU 311 determines that the fluctuation has converged, so judges YES, and proceeds to ACT 6. The CPU 311 determines that the fluctuation occurred, for example, at time TAC in FIG. 3, time TBC in FIG. 4, or time TCC in FIG. 5. The second threshold may be arbitrarily determined by the designer of the reading device 100, the creator of the information processing program, or the like.

[0038] In ACT6, the CPU 311 ends the sampling and recording. As a result, the CPU 311 performs sampling and recording, for example, during the period PAA in FIG. 3, the period PAB in FIG. 4, or the period PAC in FIG. 5. In other words, the length of the period during which the sampling and recording is performed varies depending on the fluctuation pattern of the self-interference signal. Thus, the periods PAA, PAB, and PAC during which the sampling and recording is performed are predetermined as periods during which fluctuations actually occur. These periods PAA, PAB, and PAC correspond to the first period.

[0039] In ACT 7, the CPU 311 executes a full range scan. The specific processing performed by the CPU 311 here may be similar to the processing exemplified for ACT 1, for example. In ACT8, the CPU 311 sets the gain and phase shift amount found in ACT7 to the variable attenuator 21 and the variable phase shifter 22. The specific processing by the CPU 311 here may be similar to the processing exemplified for ACT2, for example. As a result, in the case of FIG. 3, for example, the CPU 311 sets the gain determined based on the amplitude AMA to the variable attenuator 21, and sets the phase shift amount determined based on the phase PHA to the variable phase shifter 22. Also, in the case of FIG. 4, for example, the CPU 311 sets the gain determined based on the amplitude AMB to the variable attenuator 21, and sets the phase shift amount determined based on the phase PHB to the variable phase shifter 22. Also, in the case of FIG. 5, for example, the CPU 311 sets the gain determined based on the amplitude AMC to the variable attenuator 21, and sets the phase shift amount determined based on the phase PHC to the variable phase shifter 22.

[0040] In ACT9, the CPU 311 stores the pattern data in the memory 313. For example, the CPU 311 generates pattern data as data representing a set of error levels sampled and recorded in ACT4 to ACT6 in association with the gain and phase shift amount found in ACT7, and stores this in the memory 313.

[0041] In ACT 10, the CPU 311 checks whether the learning termination condition has been met. If the CPU 311 cannot confirm the event, it determines NO and returns to the standby state in ACT 3. In this way, the CPU 311 repeats the processes of ACT 3 to ACT 9 to store multiple pattern data in the memory 313.

[0042] The termination condition is determined, for example, as when the number of accumulated pattern data reaches a predetermined number as described above. However, the termination condition may be determined arbitrarily by the designer of the reading device 100 or the creator of the information processing program, such as when the number of pattern data exceeds a predetermined number and an instruction to end learning is given by an administrator or maintenance personnel. If the termination condition is met, the CPU 311 determines YES in ACT10 and proceeds to ACT11.

[0043] As ACT11, the CPU 311 creates multiple prediction models based on the pattern data accumulated as described above. The prediction models are, for example, data representing a model of the fluctuation pattern of the error level during a certain initial period of fluctuation in the self-interference signal, in association with the gain and phase shift amount. Specific information processing for creating the prediction models can be well-known processing, such as regression or k-nearest neighbor. The CPU 311 saves the created prediction models in the memory 313. If prediction models created in previous learning processes are already stored in the memory 313, the CPU 311 may overwrite those prediction models with newly created prediction models, or may additionally save the new prediction models. Once the CPU 311 has finished creating the prediction models, the learning process ends.

[0044] For example, based on a plurality of pattern data showing similar error level fluctuation patterns during the period PAA in Fig. 3, a prediction model is created by associating a fluctuation pattern model showing the trend of the error level fluctuation pattern during the period from time TAA to time TAB after the elapse of time TZA with a representative gain and phase amount based on the gain and phase amount setting trends. Based on a plurality of pattern data showing similar error level fluctuation patterns during the period PAB in Fig. 4, a prediction model is created by associating a fluctuation pattern model showing the trend of the error level fluctuation pattern during the period from time TBA to time TBB after the elapse of time TZA with a representative gain and phase amount based on the gain and phase amount setting trends. Based on a plurality of pattern data showing similar error level fluctuation patterns during the period PAC in Fig. 5, a prediction model is created by associating a fluctuation pattern model showing the trend of the error level fluctuation pattern during the period from time TCA to time TCB after the elapse of time TZA with a representative gain and phase amount based on the gain and phase amount setting trends. In other words, the fluctuation pattern models shown in each of the plurality of prediction models are all related to a period of the same length TZA. Thus, the period for predicting the model of the fluctuation pattern is predetermined as a period of time TZA starting from when the fluctuation in the error level is detected, and corresponds to the second period. Note that the time TZA may be arbitrarily determined by the designer of the reading device 100 or the creator of the information processing program. Thus, by executing the learning process based on the information processing program, the CPU 311 functions as a third generation unit.

[0045] When the reader 100 is in a normal operating state, the CPU 311 executes control processing as information processing for controlling the reduction of the self-interference signal as described above in accordance with an information processing program stored in the memory 313. FIG. 6 is a flowchart of the control process.

[0046] In ACT 21, the CPU 311 executes a full range scan. The specific processing performed by the CPU 311 here may be the same as the processing exemplified for ACT 1 in FIG. In ACT22, the CPU 311 sets the gain and phase shift amount found in ACT21 in the variable attenuator 21 and the variable phase shifter 22. The specific processing of the CPU 311 here may be the same as the processing exemplified for ACT2 in FIG. Thus, by executing the control process based on the information processing program, the CPU 311 functions as a first control unit.

[0047] In ACT 23, the CPU 311 waits for a fluctuation to occur in the self-interference signal. The specific processing of the CPU 311 here may be the same as the processing exemplified for ACT 3 in Fig. 2. If a fluctuation occurs in the self-interference signal, the CPU 311 determines YES and proceeds to ACT 24. In ACT24, the CPU 311 performs sampling and recording of the error level. Specific processing by the CPU 311 here may be similar to the processing exemplified for the sampling and recording starting in ACT4 in FIG. 2, for example. However, here, the CPU 311 performs sampling and recording only for a predetermined time. The time for performing sampling and recording is assumed to be, for example, time TZA. However, the time for performing sampling and recording may be arbitrarily determined by, for example, the designer of the reading device 100 or the creator of the information processing program, so that sampling and recording is performed for a portion of the initial period of the fluctuation period of the self-interference signal.

[0048] In ACT 25, the CPU 311 selects one of the multiple prediction models created by the learning process described above and stored in the memory 313, based on the fluctuation pattern of the error level recorded in ACT 24. For example, the CPU 311 selects a prediction model that shows a fluctuation pattern that is closest to the fluctuation pattern of the error level recorded in ACT 24. However, the rules by which the CPU 311 selects a prediction model may be arbitrarily determined by, for example, the designer of the reading device 100 or the creator of the information processing program, so that a prediction model that shows a fluctuation pattern similar to the fluctuation pattern of the error level recorded in ACT 24 is selected. Thus, the CPU 311 functions as a selection unit by executing control processing based on the information processing program.

[0049] In ACT 26, the CPU 311 checks whether the fluctuation of the self-interference signal has converged. The specific processing performed by the CPU 311 here may be the same as the processing exemplified for ACT 5 in Fig. 2. If the fluctuation of the self-interference signal has converged, the CPU 311 determines YES and proceeds to ACT 27. In ACT 27, the CPU 311 sets the gain and phase shift amount represented in the prediction model selected in ACT 25 to the variable attenuator 21 and the variable phase shifter 22. Such control of the gain and phase shift amount based on the prediction model will be referred to as primary control hereinafter. Thus, by executing the control process based on the information processing program, the CPU 311 functions as a second control unit.

[0050] In ACT28, the CPU 311 checks whether the self-interference signal is being successfully canceled by the primary control. For example, if the error level is less than a predetermined third threshold, the CPU 311 determines that the cancellation is successful and returns to ACT28. In other words, the CPU 311 maintains the settings under the primary control as long as the self-interference signal is being successfully canceled by the primary control. Therefore, if the gain and phase shift represented by the prediction model selected in ACT25 match the amplitude and phase of the self-interference signal after the fluctuations have converged and the self-interference signal is being successfully canceled, the operating state is maintained as is. Note that the third threshold may be arbitrarily determined, for example, by the designer of the reader 100 or the creator of the information processing program.

[0051] However, there is no guarantee that the gain and phase shift represented by the prediction model selected in ACT 25 will match the amplitude and phase of the self-interference signal after the fluctuations have converged, and the cancellation signal generated under primary control may not be able to sufficiently cancel the self-interference signal. Furthermore, while maintaining an operating state in which the self-interference signal is being successfully canceled as described above, the self-interference signal may fluctuate, making it impossible to sufficiently cancel the self-interference signal. In these cases, the CPU 311 determines NO in ACT 28 if, for example, the error level is equal to or greater than the third threshold, and proceeds to ACT 29.

[0052] In ACT 29, the CPU 311 checks whether the cancellation of the self-interference signal is defective. For example, if the error level is equal to or greater than a predetermined fourth threshold, the CPU 311 determines that the cancellation is defective and returns to ACT 21 as YES. Note that the fourth threshold may be arbitrarily determined by, for example, the designer of the reading device 100 or the creator of the information processing program. However, the fourth threshold is greater than the third threshold. In this way, if the cancellation signal is deviated to the extent that the error level is equal to or greater than the fourth threshold, the CPU 311 repeats ACT21 and subsequent steps to redo the adjustment of the gain and phase shift amount based on the results of the full range scan.

[0053] If the error level is not so large and is less than the fourth threshold, the CPU 311 determines that there is no cancellation failure and determines NO in ACT29, and proceeds to ACT30. In ACT 30, the CPU 311 executes a limited range scan. The limited range scan is a scan targeting a limited range narrower than the scan range in the full range scan. For example, the CPU 311 checks the error level while gradually changing the gain and phase shift amount within the limited range, and finds the combination of gain and phase shift amount that minimizes the error level. In ACT 31, the CPU 311 sets the gain and phase shift amount found in ACT 30 to the variable attenuator 21 and the variable phase shifter 22. Such control of the gain and phase shift amount based on the limited range scan will be referred to as secondary control hereinafter. In this way, the CPU 311 determines whether the error level is equal to the third threshold value. Above and the fourth threshold Execute secondary control when That is, the CPU 311 does not execute the secondary control when the error level is less than the third threshold value and when the error level is equal to or greater than the fourth threshold value. , the range of error levels below the third threshold and the range of error levels equal to or greater than the fourth threshold. corresponds to the first range.

[0054] FIG. 7 is a diagram illustrating an example of the primary control and the secondary control. The example in FIG. 7 shows a case where the CPU 311 sets the gain G and the phase shift SHA in ACT22. Then, in ACT27, the CPU 311 performs primary control by setting the gain G and the phase shift SHB represented in the selected prediction model based on the fluctuation pattern of the error level associated with fluctuations in the self-interference signal. At this time, a limited range RAA is determined based on the gain G and the phase shift SHB. The limited range RAA is a portion of the scan range RAB in the full-range scan. In this embodiment, the gain change range in the limited range RAA ranges from a gain lower than the gain G by a first specified value to a gain higher than the gain G by a first specified value. Also in this embodiment, the phase change range in the limited range RAA ranges from a phase shift lower than the phase shift SHB by a second specified value to a phase shift higher than the phase shift SHA by a second specified value. Furthermore, the CPU 311 performs secondary control in ACT31 by setting the gain GAC and the phase shift amount SHC found by the limited range scan for the limited range RAA. The range of change of the gain and phase shift amount for the limited range RAA may be determined arbitrarily by, for example, the designer of the reading device 100 or the creator of the information processing program. Also, the limited range RAA may be determined so that the shape shown in FIG. 7 is a rectangle, a circle, an ellipse, or another shape.

[0055] In ACT 32, the CPU 311 checks whether the self-interference signal has been successfully canceled by the secondary control. The specific processing of the CPU 311 here may be the same as the processing exemplified in ACT 28, for example. If the CPU 311 determines that the self-interference signal is successfully canceled (YES), the process returns to ACT 32. In other words, if the self-interference signal has been successfully canceled by the cancellation signal generated using the gain and phase shift amount found by the limited range scan, the CPU 311 maintains the settings in ACT 31.

[0056] However, the cancellation signal generated by the secondary control may not be able to sufficiently cancel the self-interference signal. Furthermore, while maintaining the operating state in which the self-interference signal is successfully canceled as described above, the self-interference signal may fluctuate, making it impossible to sufficiently cancel the self-interference signal. In these cases, the CPU 311 determines NO in ACT 32 and proceeds to ACT 33.

[0057] In ACT 33, the CPU 311 checks whether the cancellation of the self-interference signal is poor. The specific processing of the CPU 311 here may be the same as the processing exemplified for ACT 29. If the CPU 311 determines that the cancellation is not poor and returns to NO, the process returns to ACT 30. In other words, the CPU 311 redoes the secondary control in a situation where the cancellation is not good but not poor either.

[0058] If the accuracy of the prediction model or the accuracy of the selection of the prediction model is low, it is possible that the gain and phase amount within the limited range RAA determined based on the gain and phase amount represented by the selected prediction model will result in a state where the cancellation is neither good nor bad, no matter how many times the secondary control is repeated. Therefore, if there is a possibility of this happening, the CPU 311 may return to ACT 21 if the determination in ACT 33 is NO after repeating the secondary control a predetermined number of times.

[0059] If the CPU 311 determines that the cancellation is incorrect and answers YES in ACT 33, it proceeds to ACT 34. The CPU 311 performs sampling and recording of the error level in ACT 34. The specific processing of the CPU 311 here may be the same as the processing exemplified for ACT 24, for example.

[0060] In ACT 35, the CPU 311 selects a prediction model based on the fluctuation pattern of the error level recorded in ACT 34. The specific processing performed by the CPU 311 here may be the same as the processing exemplified for ACT 25, for example. However, for example, when the fourth threshold is greater than the first threshold, the time lag from when a variation occurs in the self-interference signal to when sampling recording begins may be greater than that in the sampling recording in ACT 24. Therefore, CPU 311 may set the time for performing sampling recording in ACT 34 to be shorter than that in the case of sampling recording in ACT 24. Furthermore, when selecting a prediction model in ACT 35, CPU 311 may not refer to an early part of the variation pattern represented in the prediction model. That is, if the cancellation signal generated by the secondary control is not sufficient to cancel the self-interference signal, the CPU 311 reselects a prediction model. Then, the CPU 311 returns to ACT 26 and starts over from the primary control based on the reselected prediction model.

[0061] As described above, the reader 100 creates a prediction model that takes into account actual fluctuations in the self-interference signal through learning processing, and when a large fluctuation occurs in the self-interference signal, it selects a prediction model according to the fluctuation pattern at the beginning of the fluctuation and generates a cancellation signal through primary control that applies the gain and phase shift represented in the prediction model. This eliminates the need to scan the gain and phase shift, and shortens the time required for setting up to generate a cancellation signal.

[0062] Furthermore, if the cancellation signal generated by the primary control is unable to satisfactorily cancel the self-interference signal, the reader 100 adjusts the gain and phase shift amount by secondary control, which scans the gain and phase shift amount. Therefore, a state in which the self-interference signal can be satisfactorily canceled can be created. Furthermore, because the scan related to the secondary control is limited to a limited range, the time required for the scan can be shortened compared to full-range scanning.

[0063] Furthermore, if the self-interference signal cannot be effectively canceled by the cancellation signal generated by the secondary control, the reader 100 adjusts the gain and phase shift amount again by the secondary control. Therefore, in a situation where the self-interference signal fluctuates slightly, the gain and phase shift amount can be adjusted in a short time to compensate for the fluctuation.

[0064] This embodiment can be modified in various ways as follows. It may also be realized as a communication device that communicates with the RFID tag 200 in order to write to the RFID tag 200. It may also be realized as a communication device that communicates with a communication device other than the RFID tag 200.

[0065] Some or all of the functions realized by the CPU 311 through information processing can be realized by hardware that executes information processing not based on a program, such as a logic circuit, etc. Each of the above functions can also be realized by combining hardware such as the above logic circuit with software control.

[0066] 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 embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0067] 11...oscillator, 12...phase shifter, 13...DA converter, 14...quadrature modulator, 15, 26...BPF, 16...power amplifier, 17, 29...LPF, 18...antenna duplexer, 19...feed line, 20...antenna, 21...variable attenuator, 22...variable phase shifter, 23...DA converter, 24...power combiner, 25...quadrature detector, 27...baseband amplifier, 28, 30...AD converter, 31...control unit, 311...CPU, 312...FPGA, 313...memory, 100...reader, 200...RFID tag.

Claims

1. a first generator that generates a transmission signal for wireless transmission; a common unit that receives the transmission signal generated by the first generating unit from an input terminal and outputs the signal from an input / output terminal, and that outputs the signal input from the input / output terminal from an output terminal; a second generator that generates a cancellation signal by changing the amplitude and phase of the transmission signal generated by the first generator; a combining unit that combines a cancellation signal with the signal output from the output terminal; a detection unit that detects an error level between the cancellation signal and a self-interference signal included in the output signal from the output terminal; a first control unit that controls the second generation unit to generate the cancellation signal with a gain and a phase shift amount determined in accordance with the error level detected by the detection unit; a third generation unit that records a fluctuation pattern of the error level detected by the detection unit a plurality of times during a predetermined first period after the start of fluctuation of the error level detected by the detection unit, and generates a plurality of prediction models that associate a fluctuation pattern of the error level predicted for a second period that is a part of the initial period with a gain and a phase shift amount after fluctuation convergence based on the gain and the phase shift amount respectively determined by the first control unit after the convergence of the plurality of error level fluctuations; a selection unit that selects one of the plurality of prediction models generated by the third generation unit based on the fluctuation pattern detected by the detection unit during the second period after the start of fluctuation in the error level detected by the detection unit; and a second control unit that controls the second generation unit to generate the cancellation signal with a gain and a phase shift amount represented in the prediction model selected by the selection unit; A communication device equipped with:

2. the second control unit controls the second generation unit to generate the cancellation signal with a gain and a phase determined based on error levels detected by the detection unit while changing the gain and the phase shift amount within a limited range that is a part of an adjustable range of the gain and the phase shift amount in the second generation unit. The communication device according to claim 1 .

3. the second control unit controls the second generation unit to generate the cancellation signal with a gain and a phase determined based on the error levels detected by the detection unit while changing the gain and the phase shift within the limited range when an error level detected by the detection unit for the cancellation signal generated by the second generation unit with the gain and the phase shift represented in the prediction model selected by the selection unit falls outside a first range. The communication device according to claim 2 .

4. when an error level detected by the detection unit regarding the cancellation signal generated by the second generation unit falls outside the first range, the second control unit controls the second generation unit to generate the cancellation signal with a gain and a phase determined based on the error levels detected by the detection unit while changing the gain and the phase shift amount within the limited range. The communication device according to claim 3 .

5. a detection unit that performs quadrature detection on the combined output of the combiner using a carrier wave to output two systems of received baseband signals; Furthermore, the detection unit detects an error level based on the signal levels of the two systems of received baseband signals output from the detection unit. A communication device according to any one of claims 1 to 4.

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