Communication apparatus

Abstract

To prevent a response of a radio tag when adjusting a cancel signal.SOLUTION: A communication apparatus of an embodiment, comprises: a first generation part; a sharing part; a second generation part; a pressure suppression part; and an adjustment part. The sharing part inputs a carrier wave generated by the first generation part from an input end, and outputs them from an input and output end, and outputs a signal input from the input and output end from an output end. The second generation part changes an oscillation and a phase of the carrier wave, generated by the first generation part, and generates a cancelling signal. The pressure suppression part suppresses a self-interference signal contained in the output signal from the output end by using the cancelling signal generated by the second generation part. The adjustment part adjusts the cancelling signal generated by the second generation part in accordance with the output signal from the output end while inputting the carrier wave output by the first generation part into the input end in a first period that is a length that the radio tag is not activated.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] In a communication device that shares an antenna for both transmission and reception, a part of the transmission signal may be superimposed on the reception signal and flow into the reception system. The transmission signal component superimposed on the reception signal may become a self-interference signal, which may cause saturation of the reception system and increase in noise, resulting in a deterioration of communication quality. In view of this, 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 the self-interference signal is cancelled out using the cancellation signal.

[0003] The self-interference signal varies depending on the surrounding environment, so a carrier wave is transmitted prior to receiving a response signal from a wireless tag to generate a self-interference signal, and a cancellation signal is adjusted so as to effectively cancel the self-interference signal. Incidentally, there are types of wireless tags that operate by obtaining operating power from a carrier wave transmitted from a communication device, and transmit a response signal when they become operational. This type of wireless tag may be activated by transmitting a carrier wave for adjusting the cancellation signal as described above, and may transmit a response signal. Under these circumstances, it has been desired to prevent the wireless tag from responding when adjusting the cancellation signal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-187227 A 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 prevent a wireless tag from responding when a cancellation signal is adjusted. [Means for solving the problem]

[0006] A communication device according to an embodiment receives a response signal transmitted from a wireless tag that operates using power obtained from a received carrier wave, and includes a first generating unit, a shared unit, a second generating unit, a suppressing unit, and an adjusting unit. The first generating unit generates a carrier wave. The shared unit inputs the carrier wave generated by the first generating unit from an input end and outputs it from an input / output end, and outputs a signal input from the input / output end from an output end. The second generating unit changes the amplitude and phase of the carrier wave generated by the first generating unit to generate a cancellation signal. The suppressing unit suppresses a self-interference signal included in an output signal from the output end by using the cancellation signal generated by the second generating unit. The adjusting unit adjusts the cancellation signal generated by the second generating unit according to the output signal from the output end while inputting the carrier wave output by the first generating unit to the input end during a first period that is long enough to prevent the wireless tag from activating. [Brief description of the drawings]

[0007] [Figure 1] FIG. 2 is a block diagram showing the main circuit configuration of the reading device according to the first embodiment. [Diagram 2] 4 is a flowchart of a control process according to the first embodiment. [Diagram 3] FIG. 4 is a timing diagram showing the relationship between the timing of changes in transmission power, rectified power, and response wave power. [Figure 4] 10 is a flowchart of a control process according to a second embodiment. [Diagram 5] 13 is a flowchart of a control process according to a third embodiment. [Figure 6] FIG. 13 is a diagram showing a modified example of a change in transmission power. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment 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 performs wireless communication with the RFID tag when reading the data, and is an example of a communication device. The RFID tag is an example of a wireless tag.

[0009] [First embodiment] FIG. 1 is a block diagram showing the main circuit configuration of a reading device 100 according to the first 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, an LPF 26, an alternating current (AC) coupled amplifier 27, an analog to digital (AD) converter 28, an LPF 29, an AD converter 30, a control unit 31, and a memory 32. The control unit 31 includes a CPU 311 and a field programmable gate array (FPGA) 312. 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. The oscillator 11 and the phase shifter 12 are an example of a first generating section. The DA converter 13 converts two systems of transmission baseband signals output in a digital state from the CPU 311 into analog form. In the following, the two systems of transmission baseband signals are referred to as an I signal and a Q signal, respectively.

[0011] The quadrature modulator 14 receives, as modulated waves, the I and Q signals converted into analog form by the DA converter 13. The quadrature modulator 14 receives, as I and Q system carrier waves, the carrier wave generated by the oscillator 11 and the carrier wave output from the phase shifter 12. The quadrature modulator 14 then obtains a transmission signal by quadrature modulation.

[0012] The BPF 15 removes low 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 in the BPF 15, the power amplifier 16, and the LPF 17. That is, the transmission signal for wireless transmission is generated by the BPF 15, the power amplifier 16, and the LPF 17.

[0013] 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 reception 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 reception signal below. The antenna duplexer 18 is an example of a duplexer.

[0014] The feeder line 19 supplies a transmission signal output from the input / output terminal TIO of the antenna duplexer to the antenna 20. The feeder line 19 transmits a 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 a transmission signal supplied by the power feeder 19. The antenna 20 generates an electrical signal corresponding to the incoming radio waves as a reception signal.

[0015] The variable attenuator 21 attenuates the transmission signal output from the output terminal TOB of the antenna duplexer 18 with a gain according to a gain setting signal supplied from the DA converter 23 . The variable phase shifter 22 changes the phase of the transmission signal after being attenuated by the variable attenuator 21 by an amount of phase shift corresponding 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 a function as a second generating section that generates a cancellation signal.

[0016] 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.

[0017] 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 suppression unit. The quadrature detector 25 performs quadrature detection on the received signal output from the power combiner 24, using the two carrier waves output from the oscillator 11 and the phase shifter 12, respectively. The quadrature detector 25 outputs, in parallel, two systems of analog received baseband signals obtained by quadrature detection.

[0018] The LPF 26 removes unnecessary frequency components other than the baseband components from each of the two systems of received baseband signals output from the quadrature detector 25 . The AC coupling amplifier 27 cuts the DC components of each of the two systems of received baseband signals that have passed through the LPF 26, while amplifying the AC components that correspond to the response waves.

[0019] 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 .

[0020] The memory 32 stores an information processing program describing information processing to be executed by the CPU 311. One of the information processing programs stored in the memory 32 is a control program PRA related to control processing, which will be described later. The memory 32 stores various data required for the CPU 311 to execute various information processing. The memory 32 stores various data generated or acquired when the CPU 311 executes various information processing.

[0021] 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 (described later) for adjusting the gain in 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.

[0022] 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 a process for calculating the amount of suppression of the self-interference signal by the cancellation signal, based on the levels of the two systems of received baseband signals digitized by the AD converter 30.

[0023] Next, the operation of the reading device 100 configured as above will be described. Before describing the operation, a self-interference signal will be described. The antenna duplexer 18 is designed so that the transmission 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 transmission signal input to the input terminal TI from leaking out from the output terminal TOA. For this reason, a part of the transmission signal input to the input terminal TI is output as is from the output terminal TOA. A part of the transmission signal output from the input / output terminal TIO of the antenna duplexer 18 is reflected at the power feed point of the antenna 20 and transmitted to the antenna duplexer 18 by the power feed line 19. Such a 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 contains a component of the transmission signal that is not output from the input / output terminal TIO and leaks out, and a component of the transmission signal that is input to the input / output terminal TIO as a reflected signal. A signal in which such components of the transmission signal are combined is a self-interference signal. The reflection characteristics of the transmission signal at the power feed point of the antenna 20 change depending on the surrounding environment of the antenna 20, such as the proximity of the RFID tag 200 and other objects to the antenna 20. For this reason, 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.

[0024] The self-interference signal is a signal derived from the transmission signal. Therefore, the self-interference signal included in the reception signal can be cancelled by combining a cancellation signal generated by changing the amplitude and phase of a signal branched from the transmission signal with the reception signal output from the output terminal TOA of the antenna duplexer 18. In the reader 100, the cancellation signal obtained by changing the amplitude and phase in 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 in the power combiner 24 to reduce the self-interference signal included in the reception signal.

[0025] The amplitude and phase of the self-interference signal fluctuate when another metal or the like is present near the reader 100 and the RFID tag 200, but do not change significantly when there is no such disturbance. The reader 100 reads the RFID tag 200 in a situation where there are no disturbances (hereinafter referred to as a standard situation). Even if a significant fluctuation in the self-interference signal occurs due to disturbances, it is assumed that the fluctuation will be resolved within a short period of time.

[0026] FIG. 2 is a flowchart of the control process in the first embodiment. When it becomes necessary to read the RFID tag 200, the CPU 311 executes the control process shown in FIG. 2 based on the control program PRA. In ACT1, the CPU 311 starts transmitting a carrier wave. That is, the CPU 311, for example, puts the quadrature modulator 14 into a state in which the carrier wave output from the oscillator 11 and the phase shifter 12 is output as is. In ACT2, the CPU 311 stops canceling the self-interference signal. That is, the CPU 311 stops output of the cancellation signal from the variable phase shifter 22, for example. As ACT3, the CPU 311 measures the amplitude and phase of the self-interference signal.

[0027] At this time, the reader 100 transmits a carrier wave, but the RFID tag 200 does not activate and does not transmit a response signal until the power obtained by rectifying the carrier wave (hereinafter referred to as rectified power) exceeds a certain activation power. Therefore, only the self-interference signal is input to the quadrature detector 25. Since the cancellation is stopped, the output signal of the quadrature detector 25 changes in level according to the self-interference signal. Therefore, the FPGA 312 obtains the amplitude and phase of the self-interference signal by performing a predetermined arithmetic process on the two systems of digital-state reception baseband signals output from the AD converter 30. The CPU 311, as ACT3, obtains the amplitude and phase obtained by the FPGA 312 as described above.

[0028] In ACT4, the CPU 311 starts cancellation. That is, the CPU 311 starts outputting a cancellation signal from the variable phase shifter 22. The CPU 311 sets the attenuation amount of the variable attenuator 21 and the phase amount of the variable phase shifter 22 so that the amplitude and phase of the cancellation signal are set to predetermined initial values. The initial values ​​of the amplitude and phase of the cancellation signal are set within a predetermined sweep range. The sweep range is a range that includes the amplitude and phase of a self-interference signal that may occur under standard conditions. The sweep range may be appropriately determined by, for example, a designer of the reader 100.

[0029] As ACT5, the CPU 311 sweeps the amplitude and phase of the cancellation signal within a sweep range. That is, the CPU 311 sequentially changes, for example, the attenuation amount of the variable attenuator 21 and the phase shift amount of the variable phase shifter 22 within a range that is determined in advance according to the sweep range. Then, the CPU 311 determines the attenuation amount and the phase shift amount when the level of the output signal of the quadrature detector 25 is minimum. In ACT6, the CPU 311 sets the operating states of the variable attenuator 21 and the variable phase shifter 22 to their minimum points. That is, the CPU 311 sets, for example, the amplitude and phase of the cancellation signal to the amount of attenuation and the amount of phase shift determined in ACT5.

[0030] In ACT7, the CPU 311 checks whether the specified suppression state is reached. The specified suppression state is a state in which the influence of the self-interference signal is sufficiently suppressed. More specifically, as an example, the specified suppression state is a state in which the level of the component of the self-interference signal remaining in the output signal of the quadrature detector 25 (hereinafter referred to as the residual signal) has dropped to -20db or less compared to when the signal is not suppressed. That is, the CPU 311 checks the amount of suppression measured by the FPGA 312, and if it is confirmed that the amount of suppression has dropped to -20db or less compared to when the signal is not suppressed, it determines that the specified suppression state is reached. Note that the specified suppression state is desirably determined as a state in which the minimum amount of suppression is obtained without saturating the quadrature detector 25 due to the influence of the residual signal. The specified suppression state is appropriately determined, for example, by the designer of the reader 100. For example, the level of the output signal of the quadrature detector 25 measured in ACT3 can be used as the level of the self-interference signal when the signal is not suppressed.

[0031] As an example, if the signal levels of the two received baseband signals are represented as LI and LQ, then the FPGA 312 2 +LQ 2 That is, the larger the amount of suppression, the smaller the level of the residual signal, so the amount of suppression is calculated as the level of the residual signal. If the CPU 311 confirms that the state is the specified suppression state, it judges YES in ACT7 and proceeds to ACT8. In ACT8, the CPU 311 stops transmitting the carrier wave.

[0032] Now, when the carrier wave transmitted up to this point reaches the RFID tag 200, the RFID tag 200 starts generating operating power as rectified power based on this carrier wave. However, the transmission period TA from when the CPU 311 starts transmitting the carrier wave in ACT1 to when it stops transmitting the carrier wave in ACT8 is set to be shorter than the time it takes for the rectified power in the RFID tag 200 to reach the activation voltage of the RFID tag.

[0033] The transmission period TA is mostly occupied by the period of the sweep process in ACT5. The length of the period of the sweep process in ACT5 varies depending on the size of the sweep range. Therefore, it is possible to adjust the length of the transmission period TA depending on the size of the sweep range. Since the sweep range is set to a range that includes the amplitude and phase of the self-interference signal that may occur under standard conditions as described above, the length of the transmission period TA is shorter than the time required for the rectified power in the RFID tag 200 to reach the activation voltage of the RFID tag. Thus, the CPU 311 executes information processing based on the control program PRA, and processes ACT1 to ACT8, so that the computer with the CPU 311 as the central part functions as an adjustment section.

[0034] As ACT9, the CPU 311 waits for a predetermined waiting period TB. The length of the waiting period TB is determined as appropriate by, for example, the designer of the reader 100 as the time until the rectified power that has increased in the RFID tag 200 during the transmission period TA is sufficiently reduced. In ACT 10, the CPU 311 starts transmitting a carrier wave. This carrier wave transmission continues even after it takes time for the rectified power in the RFID tag 200 to reach the startup voltage.

[0035] In ACT11, the CPU 311 reads the RFID tag 200. That is, the CPU 311 performs processing for receiving the response signal after the RFID tag 200 starts up and transmits the response signal. The processing for receiving the response signal may be the same processing as that performed by another existing reader. Then, when the CPU 311 has completed reading the response signal, it proceeds to ACT12. In ACT 12, the CPU 311 stops transmitting the carrier wave, and then ends this control process.

[0036] Now, if the reading device 100 is in the standard state, it is highly likely that the amplitude and phase of the self-interference signal are within the sweep range. Therefore, the CPU 311 judges YES in ACT7 and executes ACT8 to ACT12. However, if the reading device 100 is not in the standard state due to a metal object being in the vicinity, the CPU 311 may not be able to determine the minimum point at which the specified suppression state can be achieved by the sweep process in ACT5. In such a case, the CPU 311 judges NO in ACT7 and proceeds to ACT13.

[0037] In ACT 13, the CPU 311 counts up the number of attempts. In ACT 14, the CPU 311 checks whether the number of attempts has exceeded the limit. If the number of attempts counted up in ACT 13 has not exceeded the predetermined limit, the CPU 311 determines NO and proceeds to ACT 15. The limit is determined as appropriate by, for example, the designer of the reading device 100.

[0038] In ACT15, the CPU 311 stops transmitting the carrier wave. The CPU 311 waits for a waiting period TB in ACT 16. Then, the CPU 311 repeats ACT 1 and subsequent steps in the same manner as described above. Thus, the CPU 311 repeats ACT1 to ACT7 and ACT13 to ACT16 until the reader 100 returns to the standard state and the minimum point at which the specified suppression state is reached can be determined by sweeping the amplitude and phase within the predetermined sweep range. At this time, the transmission of the carrier wave is repeated for a transmission period TA with a waiting period TB therebetween, so that the rectified power in the RFID tag 200 does not reach the activation voltage.

[0039] Then, when the reading device 100 has returned to the standard state and the CPU 311 has been able to determine the minimum point at which the specified suppression state is achieved by sweeping the amplitude and phase within the predetermined sweep range, the CPU 311 executes ACT8 to ACT12. Thus, the CPU 311 executes information processing based on the control program PRA, and processes ACT3, ACT21, ACT4, and ACT6 to ACT8, so that the computer with the CPU 311 as the central part functions as an adjustment section.

[0040] FIG. 3 is a timing diagram showing the relationship between the timing of changes in the transmission power, the rectified power, and the response wave power. FIG. 3 shows an example of a case where the minimum point at which the specified suppression state is achieved can be determined when ACT1 to ACT6 in FIG. 2 are executed for the fifth time.

[0041] Now, if the number of attempts counted in ACT1 to ACT6 in ACT13 exceeds the limit, the CPU 311 judges YES in ACT14 and proceeds to ACT17. In ACT17, the CPU 311 stops transmitting the carrier wave. As ACT18, the CPU 311 executes error processing. For example, as error processing, the CPU 311 executes processing for displaying an error to inform the operator that the environment is not appropriate for reading. As error processing, the CPU 311 may execute other processing, such as playing back a voice message. Furthermore, the CPU 311 may execute multiple types of processing as error processing. Then, when the CPU 311 finishes error processing, it ends the current control processing.

[0042] [Second embodiment] The main circuit configuration of the reading device according to the second embodiment is similar to that of the first embodiment, so it will not be illustrated again and will be described below as the reading device 100. The reading device 100 according to the second embodiment differs from the reading device 100 according to the first embodiment in the contents of the control process represented by the control program PRA. Thus, the operation of the reading device 100 in the second embodiment differs from that of the reading device 100 in the first embodiment in the contents of the control process.

[0043] FIG. 4 is a flowchart of a control process in the second embodiment. In FIG. 4, the same processes as those shown in FIG. 2 are denoted by the same reference numerals. The CPU 311 executes ACT1 to ACT3 in the same manner as in the first embodiment. As ACT21, the CPU 311 calculates the amplitude and phase that are the minimum points within a range similar to the sweep range in the first embodiment.

[0044] After this, the CPU 311 starts cancellation in ACT4, and then proceeds to ACT6 without performing ACT5. Then, in ACT6, the CPU 311 sets the operating states of the variable attenuator 21 and the variable phase shifter 22 to the minimum points calculated in ACT21. Except for the above points, the control process in the second embodiment is similar to that in the first embodiment.

[0045] [Third embodiment] The main circuit configuration of the reading device according to the third embodiment is similar to that of the first embodiment, so it will not be illustrated again and will be described below as the reading device 100. The reading device 100 according to the third embodiment differs from the reading device 100 according to the first embodiment in the contents of the control process represented by the control program PRA. Thus, the operation of the reading device 100 in the third embodiment differs from that of the reading device 100 in the first embodiment in the contents of the control process.

[0046] FIG. 5 is a flowchart of a control process in the third embodiment. In Fig. 5, the same processes as those shown in Fig. 2 are denoted by the same reference numerals. Also, in Fig. 5, many of the processes that are the same as those shown in Fig. 2 are omitted from the illustration. The CPU 311 executes ACT1 to ACT4 in the same manner as in the first embodiment. Then, when the CPU 311 finishes ACT4, it proceeds to ACT31.

[0047] As ACT31, the CPU 311 sets a sweep range. Here, the third embodiment sequentially sweeps a range including the amplitude and phase of a self-interference signal that may occur under normal circumstances, that is, a plurality of sweep ranges determined by dividing the sweep ranges in the first and second embodiments into a plurality of ranges. Here, the CPU 311 sets one of the plurality of sweep ranges previously set as described above as the sweep range for the sweep process to be performed.

[0048] However, the range covered by the multiple sweep ranges in the third embodiment may be different in size from the sweep ranges in the first and second embodiments. For example, it is assumed that the range covered by the multiple sweep ranges in the third embodiment is set to be larger than the sweep ranges in the first and second embodiments. Note that the range covered by the multiple sweep ranges in the third embodiment and the number of divisions thereof may be appropriately determined by, for example, the designer of the reading device 100.

[0049] In ACT 32, the CPU 311 performs a sweep process on the sweep range set in ACT 31. This sweep process may be the same as the sweep process in ACT 5 in FIG. 2, although the sweep range is different. In ACT 33, the CPU 311 checks whether the sweep process for each of the plurality of sweep ranges has been completed. If there is a sweep range among the plurality of sweep ranges for which the sweep process has not yet been performed, the CPU 311 judges the result as NO and proceeds to ACT 34.

[0050] As ACT34, the CPU 311 stops transmitting the carrier wave. In ACT35, the CPU 311 waits during a waiting period TB. In ACT36, CPU311 starts transmitting a carrier wave. Then, CPU311 repeats ACT31 and subsequent steps. When CPU311 returns from ACT36 to ACT31, it sets a sweep range different from the sweep range selected in ACT31 while repeating ACT31 to ACT36 up to this point as the target of the next sweep process in ACT31. As a result, CPU311 repeats ACT31 to ACT36 to sequentially perform sweep processes targeting each of the multiple sweep ranges.

[0051] Then, when the sweep process for each of the plurality of sweep ranges is completed, the CPU 311 judges YES in ACT 33 and proceeds to ACT 37. In ACT 37, the CPU 311 determines the minimum point among the minimum points determined in each of the multiple sweep processes. Then, the CPU 311 executes the processes from ACT 6 onwards in the same manner as in the first embodiment. Thus, the CPU 311 executes information processing based on the control program PRA, and processes ACT3, ACT31 to ACT37, and ACT6 to ACT8, so that the computer with the CPU 311 as the central part functions as an adjustment section.

[0052] As described above, in the reader 100 of each embodiment, the transmission period TA of the carrier wave for transmitting the cancellation signal is set to a length that prevents the rectified power from reaching the activation voltage in the RFID tag 200. This makes it possible for the reader 100 to prevent the wireless tag from responding when the cancellation signal is adjusted.

[0053] Furthermore, when the reader 100 transmits the carrier signal multiple times, a waiting period TB is provided so that the multiple carrier transmissions do not cause the rectified power to reach the activation voltage in the RFID tag 200. As a result, the reader 100 can prevent the wireless tag from responding when the cancellation signal is adjusted, even if multiple carrier transmissions are required.

[0054] Furthermore, the reader 100 of the third embodiment performs a sweep process on a different sweep range in a plurality of carrier transmission periods TA sandwiched between standby periods TB. Therefore, it is possible to perform a sweep on a range wider than the sweep range that can be realized in one transmission period TA and determine the minimum point without causing the rectified power in the RFID tag 200 to reach the activation voltage.

[0055] This embodiment can be modified in various ways as follows. In all of the first, second and third embodiments, as shown in FIG. 6, a low output period TC in which the output of the carrier wave is sufficiently reduced while the carrier wave transmission continues may be provided instead of the waiting period TB.

[0056] Each function realized by the CPU 311 through information processing can be realized in part or in whole by hardware that executes information processing not based on a program, such as a logic circuit, etc. Also, each of the above functions can be realized by combining hardware such as the above logic circuit with software control.

[0057] Although some 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, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0058] 11...oscillator, 12...phase shifter, 13...DA converter, 14...quadrature modulator, 15...BPF, 16...power amplifier, 17...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, 26...LPF, 27...AC coupled amplifier, 28...AD converter, 29...LPF, 30...AD converter, 31...control unit, 311...CPU, 312...FPGA, 32...memory, 100,300...reader, 200...RFID tag.

Claims

1. A communication device that receives a response signal transmitted from a wireless tag that operates using power obtained from a received carrier wave, A first generating unit that generates the carrier wave; a common section that receives the carrier wave generated by the first generating section from an input terminal and outputs the carrier wave from an input / output terminal, and outputs a signal input from the input / output terminal from an output terminal; A second generating unit that generates a cancellation signal by changing the amplitude and phase of the carrier wave generated by the first generating unit; a suppression unit that suppresses a self-interference signal included in an output signal from the output terminal by using a cancellation signal generated by the second generation unit; an adjustment unit that adjusts a cancellation signal generated by the second generation unit in response to an output signal from the output terminal while inputting the carrier wave output by the first generation unit to the input terminal during a first period of time during which the wireless tag is not activated; A communication device equipped with the above.

2. When the adjustment unit is unable to completely adjust the cancellation signal in the first period, the adjustment unit stops the input of the carrier wave to the input end for a second period having a predetermined length, and then adjusts the cancellation signal generated by the second generation unit according to the output signal from the output end while inputting the carrier wave output by the first generation unit to the input end again in the first period. The communication device according to claim 1 .

3. When the adjustment unit is unable to completely adjust the cancellation signal in the first period, the adjustment unit reduces an input level of the carrier wave to the input end in a second period having a predetermined length, and then adjusts the cancellation signal generated by the second generation unit in accordance with the output signal from the output end while inputting the carrier wave output by the first generation unit to the input end again in the first period. The communication device according to claim 1 .

4. A communication device that receives a response signal transmitted from a wireless tag that operates using power obtained from a received carrier wave, A first generating unit that generates the carrier wave; a common section that receives the carrier wave generated by the first generating section from an input terminal and outputs the carrier wave from an input / output terminal, and outputs a signal input from the input / output terminal from an output terminal; A second generating unit that generates a cancellation signal by changing the amplitude and phase of the carrier wave generated by the first generating unit; a suppression unit that suppresses a self-interference signal included in an output signal from the output terminal by using a cancellation signal generated by the second generation unit; an adjustment unit that creates a state in which the carrier wave output by the first generation unit is input to the input terminal during a first period having a length in which the wireless tag is not activated, while sandwiching a state in which the carrier wave is not input to the input terminal during a second period having a predetermined length, and adjusts a cancellation signal generated by the second generation unit in response to an output signal from the output terminal during the multiple first periods; A communication device equipped with the above.

5. A communication device that receives a response signal transmitted from a wireless tag that operates using power obtained from a received carrier wave, A first generating unit that generates the carrier wave; a common section that receives the carrier wave generated by the first generating section from an input terminal and outputs the carrier wave from an input / output terminal, and outputs a signal input from the input / output terminal from an output terminal; A second generating unit that generates a cancellation signal by changing the amplitude and phase of the carrier wave generated by the first generating unit; a suppression unit that suppresses a self-interference signal included in an output signal from the output terminal by using a cancellation signal generated by the second generation unit; an adjustment unit that creates a state in which the carrier wave output by the first generation unit is input to the input terminal during a first period having a length during which the wireless tag is not activated, while interposing a state in which an input level of the carrier wave to the input terminal is reduced during a second period having a predetermined length, and adjusts a cancellation signal generated by the second generation unit in response to an output signal from the output terminal during the multiple first periods; A communication device equipped with the above.

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