Reader Device

Abstract

To provide a reader device that can read out from two types of transponders in a short period of time.SOLUTION: A reader device of an embodiment of the present invention comprises a transmission section, a cancellation section, and a decryption section. The transmission section transmits a wave obtained by modulating a carrier wave with a modulation signal representing a command to be given to a first transponder, as an interrogation wave. The cancellation section cancels modulation components according to the modulation signal from the wave returned from a second transponder different from the first transponder as a response wave, the second transponder being compliant with back scatter communication. The decryption section decodes data represented by the response wave in which the modulation components have been canceled by the cancellation section.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Wireless tags are broadly divided into RTF (reader talk first) tags and TTF (tag talk first) tags. RTF tags respond to commands contained in the modulated portion of radio waves transmitted from a reader, according to standards such as the EPC Global Gen2 standard. When TTF tags receive radio waves transmitted from a reader, they simply detect the incoming radio waves, regardless of whether the radio waves are modulated or unmodulated, and then perform a backscatter response. For this reason, when a reader sends a command to read an RTF tag located close to a TTF tag, the TTF tag may also respond. Therefore, by setting the TTF tag to an FM0 response and the RTF tag to a mirror subcarrier response, the response waves from the TTF tag and the RTF tag have different frequency bands, making it possible to extract the individual response waves using a filter.

[0003] However, ASK (amplitude shift keying) is used to wirelessly transmit commands for reading RTF tags. Therefore, the response wave from the TTF tag contains ASK-modulated wave components while the reader is sending the command, making it impossible to guarantee that the response data can be correctly decoded. Therefore, the reader ignores the response from the TTF tag while reading the RTF tag. In other words, if the reader is intended to read both RTF and TTF tags, it must read the RTF tag and the TTF tag separately, which increases the time required to read both tags. In view of these circumstances, it has been desired to be able to reduce the time required to read both types of responders such as RTF tags and TTF tags. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-304008 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a communication device that can reduce the time required to read both types of transponders. [Means for solving the problem]

[0006] The reader device of the embodiment includes a transmitter, a canceller, and a decoder. The transmitter transmits a query wave obtained by modulating a carrier wave with a modulation signal representing a command to be given to a first responder. The canceller cancels a modulated component corresponding to the modulation signal from a response wave transmitted by a second responder different from the first responder using a backscattering method. The decoder decodes data represented in the response wave after the modulation component has been canceled by the canceller. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a block diagram showing the main circuit configuration of a reader device according to an embodiment. [Figure 2] FIG. 2 is a block diagram illustrating an example of the configuration of an inverse modulator in FIG. 1. [Figure 3] A diagram showing the radio waves sent and received when reading an RTF tag. [Figure 4] FIG. 10 is a diagram showing the spectra of response waves from an RTF tag and a TTF tag. [Figure 5] 2 is a diagram showing how signal states change due to various processes in the reader device shown in FIG. 1. [Figure 6] FIG. 10 is a block diagram showing the main circuit configuration of a reader device according to a modified embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings, taking as an example a reader device that reads data stored in an RFID tag. FIG. 1 is a block diagram showing the main circuit configuration of a reader device 100 according to this embodiment. The reader device 100 reads data stored in RFID (radio frequency identification) tags 201 and 202.

[0009] The RFID tag 201 is an RTF tag. The RFID tag 202 is a TTF tag. Therefore, in the following, when it is necessary to distinguish between an RTF tag and a TTF tag, they will be referred to as "RTF tag 201" and "TTF tag 202," and when there is no need to distinguish between them, they will be referred to as "RFID tags 201, 202." The RTF tag is an example of a first transponder. The TTF tag 202 is an example of a second transponder.

[0010] The reader device 100 includes an oscillator 11, a phase shifter 12, a DAC (digital to analog converter) 13, an ASK modulator 14, a BPF (band-pass filter) 15, a power amplifier 16, an LPF (low-pass filter) 17, an antenna duplexer 18, a feeder line 19, an antenna 20, a vector modulator 21, a DAC 22, a power combiner 23, an inverse modulator 24, a quadrature detector 25, a BPF (band-pass filter) 26, a VGA (variable-gain amplifier) ​​27, an ADC (analog to digital converter) 28, an LPF 29, a VGA 30, an ADC 31, an LPF 32, an ADC 33, a control unit 34, a display unit 35, and an operation unit 36. The antenna 20 may not be included in the reader device 100, and any antenna may be connectable to the feeder line 19. Furthermore, the antenna 20 and the power feeder 19 may not be included in the reader device 100, and any power feeder connected to any antenna may be connectable to the antenna duplexer 18.

[0011] The reader device 100 is typically realized as a single device equipped with all of the above components. However, the reader device 100 may also be realized by connecting multiple devices equipped with the above components separately via wired or wireless connections. An example of the latter implementation is connecting a mobile information terminal equipped with a control unit 34, a display unit 35, and an operation unit 36 ​​to a communication unit equipped with the other components.

[0012] 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.

[0013] The DAC 13 converts the quadrature transmission baseband signal output in digital form from the control unit 34 into an analog signal. The ASK modulator 14 changes the amplitude of the carrier wave generated by the oscillator 11 to obtain an ASKed transmission signal. In this embodiment, the ASK modulator 14 is configured using a quadrature modulation circuit. A quadrature transmission baseband signal that does not cause a frequency shift but only causes an amplitude change is provided from the control unit 34 to the quadrature modulation circuit via the DAC 13, thereby obtaining an ASKed transmission signal.

[0014] The BPF 15 removes low-frequency and high-frequency components from the transmission signal obtained by the ASK 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 .

[0015] 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 and the self-interference signal generated at the antenna 20, and this signal will be simply referred to as the reception signal hereinafter.

[0016] 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.

[0017] The vector modulator 21 modulates the transmission signal output from the output terminal TOB of the antenna duplexer 18 so that it becomes a signal having an amplitude and phase according to the vectors represented by the quadrature control signals (hereinafter referred to as I control signal and Q control signal) from the DAC 22. The transmission signal modulated by the vector modulator 21 will be referred to as a cancellation signal below. The DAC 22 converts the I control signal and Q control signal outputted in digital form from the control unit 34 into analog signals, and obtains the I control signal and Q control signal to be supplied to the vector modulator 21 . The power combiner 23 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 vector modulator 21. In this way, the power combiner 23 reduces the self-interference signal included in the received signal.

[0018] The inverse modulator 24 receives the I and Q orthogonal baseband signals input to the ASK modulator 14. The inverse modulator 24 inversely modulates the received signal output from the power combiner 23 using the modulated wave. The quadrature detector 25 performs quadrature detection on the received signal after being inversely modulated by the inverse modulator 24, using two carrier waves with a phase difference of 90 degrees that are output from the oscillator 11 and the phase shifter 12. The quadrature detector 25 outputs, in parallel, the analog received baseband signals obtained by the quadrature detection.

[0019] The BPF 26 extracts components of a predetermined frequency band from each of the received baseband signals output from the quadrature detector 25. The passband of the BPF 26 is a frequency band predetermined for the mirror subcarrier response. In other words, the BPF 26 extracts a signal corresponding to the response wave from the RTF tag 201 from the received baseband signals. The VGA 27 amplifies each of the received baseband signals that have passed through the BPF 26 by a gain instructed by the control unit 34 so that the signal level is suitable for digitization by the ADC 28 . The ADC 28 digitizes each of the received baseband signals amplified by the VGA 27 . Thus, the BPF 26 , VGA 27 and ADC 28 constitute a processing system for a received baseband signal corresponding to a response wave from the RTF tag 201 .

[0020] The LPF 29 extracts components of a predetermined frequency band from each of the received baseband signals output from the quadrature detector 25. The passband of the LPF 26 is a frequency band predetermined for the FM0 response. In other words, the LPF 26 extracts a signal corresponding to the response wave from the TTF tag 202 from the received baseband signals. The VGA 30 amplifies each of the received baseband signals that have passed through the LPF 29 by a gain instructed by the control unit 34 to bring the signals to a level suitable for digitization by the ADC 31 . The ADC 31 digitizes each of the received baseband signals amplified by the VGA 30 . Thus, the LPF 29 , VGA 30 and ADC 31 constitute a processing system for a received baseband signal corresponding to a response wave from the TTF tag 202 .

[0021] LPF 32 extracts low frequency bands corresponding to the self-interference signal components contained in each of the received baseband signals output from quadrature detector 25. The signals extracted by LPF 32 include the self-interference signal components remaining in the output of power combiner 23. Therefore, the signals extracted by LPF 32 are hereinafter referred to as an I residual signal and a Q residual signal. The ADC 33 digitizes the I residual signal and the Q residual signal output from the LPF 32 . Thus, the LPF 32 and the ADC 33 constitute a processing system for the self-interference signal.

[0022] The control unit 34 includes a CPU (central processing unit) 341 , square adder circuits 342 and 343 , binarization circuits 344 and 345 , an SJC control circuit 346 , and a register 347 . The CPU 341 outputs a transmission baseband signal in accordance with a predetermined sequence when communicating with the RTF tag 201. The CPU 341 reconstructs the data sent from the RTF tag 201 based on the received signal output from the binarization circuit 344. The CPU 341 reconstructs the data sent from the RTF tag 202 based on the received signal output from the binarization circuit 345.

[0023] The square addition circuit 342 squares each of the received baseband signals output from the ADC 28, adds them together, and outputs the sum. The square addition circuit 343 squares each of the received baseband signals output from the ADC 31, adds them together, and outputs the sum. The binarization circuit 344 binarizes the output value from the square addition circuit 343 using a predetermined threshold value. The binarization circuit 345 binarizes the output value from the square addition circuit 343 using a predetermined threshold value.

[0024] The SJC control circuit 346 controls the vector modulator 21 for SJC (self-jammer cancellation) processing to cancel the self-interference signal. For example, the SJC control circuit 346 determines the amplitude and phase of a cancellation signal for reducing the self-interference signal based on the I residual signal and Q residual signal output from the ADC 33, and provides the I control signal and Q control signal to the vector modulator 21 to output a cancellation signal having the determined amplitude and phase.

[0025] The register 347 temporarily stores various data exchanged between the CPU 341 and the SJC control circuit 346 for SJC processing. Under the control of the CPU 341, the display unit 35 displays various information to be notified to the user, such as the results of reading the RFID tags 201 and 202. The operation unit 36 ​​inputs various instructions from the user relating to the operation of the reader device 100 and notifies the CPU 341 of the contents of the instructions.

[0026] FIG. 2 is a block diagram showing an example of the configuration of the inverse modulator 24. As shown in FIG. The inverse modulator 24 includes a phase shifter 241 , inverting amplifier circuits 242 and 243 , offset adding circuits 244 and 245 , integrating circuits 246 and 247 , and an adding circuit 248 . The received signal output from the power combiner 23 is input to the phase shifter 241. The phase shifter 241 shifts the phase of the input received signal by 90 degrees.

[0027] The inverting amplifier circuit 242 receives the I modulated signal output from the DAC 13. The inverting amplifier circuit 243 receives the Q modulated signal output from the DAC 13. The inverting amplifier circuits 242 and 243 invert the polarity of each modulated signal input, and adjust the amplitude of the signal. The offset addition circuit 244 receives as input the I modulated signal output from the inverting amplifier circuit 242. The offset addition circuit 245 receives as input the Q modulated signal output from the inverting amplifier circuit 243. The offset addition circuits 244 and 245 add predetermined offset values ​​to the input I modulated signal and Q modulated signal, respectively, so as to cancel out offset components that occur in the I modulated signal and Q modulated signal due to the offset voltages of the inverting amplifier circuits 242 and 243.

[0028] The integration circuit 246 receives as input the received signal output from the power combiner 23 and the I-modulated signal output from the offset adding circuit 244. The integration circuit 247 receives as input the received signal output from the phase shifter 241 and the Q-modulated signal output from the offset adding circuit 245. The integration circuits 246 and 247 each integrate the input received signal with the I-modulated signal or the Q-modulated signal. The adder circuit 248 adds the outputs of the integrator circuits 246 and 247. The output of the adder circuit 248 is input to the quadrature detector 25 as the output of the inverse modulator 24.

[0029] Next, the operation of the reader device 100 configured as above will be described. When reading the RTF tag 201, the CPU 341 changes the transmission baseband signal to be output to the DAC 13 in order to change the transmission signal according to a predetermined sequence. Note that various sequences for reading the RTF tag 201 are known, and any of them may be used, but the following describes a specific example in which the EPC Global Gen2 standard is applied.

[0030] FIG. 3 is a diagram showing the state of radio waves transmitted and received when reading the RTF tag 201. 3, QWA represents a change in the state of the radio wave (hereinafter referred to as the interrogation wave) emitted from the antenna 20 by the CPU 341 changing the transmission baseband signal as described above. RWA represents a change in the state of the reply wave from the RTF tag 201 in response to the interrogation wave. RWB represents a change in the state of the reply wave from the TTF tag 202 in response to the interrogation wave.

[0031] In period PA, the interrogation wave is an unmodulated carrier wave (CW). In period PB, the interrogation wave is ASKed by a modulated signal representing a Select command. In period PC, the interrogation wave is an unmodulated carrier wave. In period PD, the interrogation wave is ASKed by a modulated signal representing a Query command. In period PE, the interrogation wave is an unmodulated carrier wave. In period PF, the interrogation wave is ASKed by a modulated signal representing an Ack command. In period PE, the interrogation wave is an unmodulated carrier wave.

[0032] Such an interrogation wave is transmitted from the antenna 20 by passing the transmission baseband signal, which is converted by the CPU 341, through various processes in the DAC 13, ASK modulator 14, BPF 15, power amplifier 16, LPF 17 and antenna duplexer 18, to the antenna 20 via a feeder line 19. Thus, these components realize the function of a transmitting unit that transmits an interrogation wave representing a command to be given to the RTF tag 201, which serves as the first transponder.

[0033] If the RTF tag 201 corresponds to the tag specified by the Select command, it responds to the Query command by backscattering RN16 during the period PE. RN16 is a 16-bit random number. Then, in response to receiving an Ack command related to the RN16 it sent during the period PF, the RTF tag 201 backscatters the response data it has stored during the period PG. The response data includes an ID (identifier) ​​for identifying the RTF tag 201.

[0034] When the TTF tag 202 receives the carrier wave transmitted as the interrogation wave, it responds by backscattering the response data stored in itself, including an ID for identifying the TTF tag 202.

[0035] FIG. 4 is a diagram showing the spectra of the response waves from the RTF tag 201 and the TTF tag 202. f0 is the frequency of the unmodulated carrier wave. When the TTF tag 202 transmits backscatter, it reflects the unmodulated carrier wave using the FMO method, keeping the frequency intact. Therefore, the response wave from the TTF tag 202 has a spectrum SPA centered on the frequency f0. When transmitting backscatter, the RTF tag 201 reflects the unmodulated carrier wave using the mirror subcarrier method, while shifting the frequency by ±200 kHz. As a result, the response wave from the RTF tag 201 has a spectrum SPB, SPC centered at f0 ±200 kHz.

[0036] The received signal generated in the antenna 20 by the response wave from the RTF tag 201 or TTF tag 202 is input to the power combiner 23 via the feeder 19 and the antenna duplexer 18. The received signal is then combined with the cancellation signal output from the vector modulator 21 by the power combiner 23, thereby reducing the self-interference signal generated in the antenna duplexer 18 and the feeder 19. The received signal is then input to the inverse modulator 24.

[0037] In the inverse modulator 24, the received signal is inverted and amplified by the inverting amplifier circuit 242, and the I-modulated signal is accumulated in the integrator circuit 246. The received signal also has its phase shifted by 90 degrees by the phase shifter 241, and the Q-modulated signal is inverted and amplified by the inverting amplifier circuit 243, and accumulated in the integrator circuit 247. The received signals output from the integrator circuits 246 and 247 are then added together by the adder circuit 248. As a result, the output of the adder circuit 248 is a signal obtained by inversely modulating the received signal output from the power combiner 23 with the I-modulated signal and Q-modulated signal used for ASK in the ASK modulator 14. In other words, if the received signal output from the power combiner 23 contains an ASK-modulated component, the inverse modulator 24 cancels this modulated component. Thus, the inverse modulator 24 functions as a cancellation unit.

[0038] FIG. 5 is a diagram showing how the signal state changes due to various processes in the reader device 100. Signal SC represents the response wave when the TTF tag 202 receives the interrogation wave in the state represented by signal SA and transmits response data represented by signal SB via backscattering. Signal SC shown in Fig. 5 contains a mixture of amplitude changes due to ASK in the interrogation wave and amplitude changes corresponding to changes in reflectivity due to the response data, and its amplitude changes in three stages.

[0039] The received signal after the reverse modulation is quadrature detected by the quadrature detector 25. From each of the received baseband signals obtained by the quadrature detector 25, components in the frequency band of the mirror subcarrier response are extracted by the BPF 26. Furthermore, from each of the received baseband signals obtained by the quadrature detector 25, components in the frequency band of the FM0 response are extracted by the LPF 29. Thus, the signal component related to the response data from the RTF tag 201 is amplified by the VGA 27, digitized by the ADC 28, and provided to the control unit 34. Furthermore, the signal component related to the response data from the TTF tag 202 is amplified by the VGA 30, digitized by the ADC 31, and provided to the control unit 34. In this way, the BPF 26 and the LPF 29 function as a separator.

[0040] The received baseband signal for the RTF tag 201 is square-added by a square-adding circuit 342, and the received baseband signal for the TTF tag 202 is square-added by a square-adding circuit 343. As a result of these square-adding operations, signals having signal levels corresponding to the amplitude of the reply wave are output from the square-adding circuits 342 and 343.

[0041] When the RTF tag 201 transmits the RN16 and response data, the interrogation wave is an unmodulated carrier wave, and the response wave contains two amplitude fluctuations based solely on the response data. Because no level fluctuations occur in the modulated signal during this period, the inverse modulator 24 does not perform inverse modulation, and the received signal passes through the inverse modulator 24 unchanged. Thus, when the received signal is input to the quadrature detector 25, it contains two amplitude fluctuations based solely on the response data from the RTF tag 201. As a result, the output of the square summation circuit 342 is a signal whose level changes in the same way as the response data from the RTF tag 201. In other words, the response data from the RTF tag 201 can be decoded by binarizing the output of the square summation circuit 342 using an appropriate threshold value in the binarization circuit 344. In this way, the square summation circuit 342 and the binarization circuit 344 function as a decoder that decodes the data contained in the response wave transmitted by the RTF tag 201 (the first responder).

[0042] As described above, when the TTF tag 202 transmits response data in response to the carrier wave component transmitted from the reader device 100 to read the RTF tag 201, the ASK modulation component remains in the response wave for periods PB, PD, and PF in Fig. 3, resulting in a three- or four-stage amplitude fluctuation, for example, like the signal SC in Fig. 5. Therefore, unlike the response data, the output of the square addition circuit 343 is a signal whose level changes in three or more stages, for example, like the signal SD.

[0043] When signal SD is binarized using threshold value TH, the result is signal SE, which does not match signal SB, the response data. In other words, the binarization result is not a signal that correctly decodes the response data. However, in this embodiment, by inversely modulating a response wave such as signal SC with an inverse modulation signal such as signal SF, the received signal becomes a signal such as signal SG that contains only two stages of amplitude fluctuation corresponding to the response data.

[0044] Thus, the output of the square summing circuit 343 becomes a signal with two-stage amplitude fluctuations like the signal SH, and the signal SB can be decoded with high accuracy by binarizing it at the threshold value TH in the binarization circuit 345. In this way, the square summing circuit 343 and the binarization circuit 345 realize the function of a decoding unit that decodes the data contained in the reply wave transmitted by the TTF tag 202 as the second responder.

[0045] As described above, the reader device 100 can errorlessly demodulate the response data from the TTF tag 202 when the TTF tag 202 responds while reading the RTF tag 201. In other words, it is possible to simultaneously read the RTF tag 201 and the TTF tag 202, thereby improving the efficiency of reading when both the RTF tag 201 and the TTF tag 202 are being read.

[0046] This embodiment can be modified as follows. FIG. 6 is a block diagram showing the main circuit configuration of a reader device 101 as a modified embodiment. In FIG. 6, the same elements as those shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. The reader device 101 includes the same components as the reader device 100. However, the reader device 101 differs from the reader device 100 in the arrangement of the inverse modulator 24. In the reader device 101, the modulated wave output from the power combiner 23 is input directly to the quadrature detector 25. The carrier wave output from the oscillator 11 is input to the inverse modulator 24. Thus, the inverse modulator 24 applies inverse modulation to the carrier wave. The inversely modulated carrier wave and a carrier wave obtained by shifting the phase of the inversely modulated carrier wave by 90 degrees using the phase shifter 12 are input to the quadrature detector 25. Even with this configuration, the output from the quadrature detector 25 is the same as that of the reader device 100, and the same effects as those of the reader device 100 can be obtained.

[0047] 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]

[0048] 11...oscillator, 12...phase shifter, 13, 22...DAC, 14...ASK modulator, 15...BPF, 16...power amplifier, 17...LPF, 18...antenna duplexer, 19...feed line, 20...antenna, 21...vector modulator, 23...power combiner, 24...inverse modulator, 25...quadrature detector, 26...BPF, 27, 30...VGA, 28, 31, 33...ADC, 29, 32...LPF, 34...control unit, 35...display unit, 36...operation unit, 1 00,101...reader device, 201...RFID tag, RTF tag, 202...RFID tag, TTF tag, 241...phase shifter, 242,243...inverting amplifier circuit, 244,245...offset addition circuit, 245...offset addition circuit, 246,247...integration circuit, 248...addition circuit, 341...CPU, 342,343...square addition circuit, 344,345...binarization circuit, 346...SJC control circuit, 347...register.

Claims

1. a transmitter for transmitting an interrogation wave obtained by modulating a carrier wave with a modulation signal representing a command to be given to the first responder; a canceling unit that cancels a modulated component corresponding to the modulated signal from a reply wave transmitted by a second responder different from the first responder using a backscattering method; a decoding unit that decodes data represented in the response wave after the modulation component has been canceled by the canceling unit; A reader device comprising:

2. the canceller cancels the modulated component by applying inverse modulation to the received signal corresponding to the reply wave using the modulated signal. The reader device according to claim 1 .

3. the canceller cancels the modulated component by removing a component of a local signal obtained by inversely modulating the carrier wave with the modulated signal from the response wave. The reader device according to claim 1 .

4. the canceling unit cancels a modulated component corresponding to the modulated signal from a received signal corresponding to a received wave including a first response wave transmitted from the first responder in a first frequency band in response to the command included in the interrogation wave and a second response wave transmitted from the second responder in a second frequency band in response to the interrogation wave; a separation unit that separates a first signal of the first frequency band component and a second signal of the second frequency band component from the received signal after the modulation component has been canceled by the cancellation unit, and the decoding unit decodes data represented in the first reply wave from the first signal separated by the separation unit, and decodes data represented in the second reply wave from the second signal separated by the separation unit. A reader device according to any one of claims 1 to 3.

5. the second frequency band is the same frequency band as the interrogation wave, and the first frequency band is a frequency band shifted by a specified amount from the frequency band of the interrogation wave; The reader device according to claim 4 .

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