Communication device and communication method

Abstract

To prevent transmission data from a wireless tag to the other reader from being erroneously received, without complicating a configuration of the wireless tag.SOLUTION: A communication device comprises respective units for orthogonal modulation, transmission, reception, orthogonal detection, first demodulation, first decoding, second demodulation, second decoding, generation, comparison and processing. In the generation unit, a first I signal and a first Q signal are generated and inputted to the orthogonal modulation unit as a signal to perform frequency shift modulation on a carrier wave with modulation data. In the first demodulation unit and the first decoding unit, pieces of first data on which amplitude shift modulation is performed and which are transmitted from a wireless tag are demodulated and decoded. In the second demodulation unit and the second decoding unit, pieces of second data on which the frequency shift modulation is performed are demodulated and decoded from a radio signal from the wireless tag. The comparison unit compares the second data with the modulation data. In a case where the comparison unit confirms matching of the second data and the modulation data, the processing unit performs data processing for the first data.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE The present invention relates to a communication device and a communication method. [Background technology]

[0002] When a wireless tag is located in a position where the communication ranges of multiple readers using the same transmission frequency band overlap, it is impossible to identify which of the multiple readers the reflected wave from the wireless tag corresponds to. One possible solution to this problem is to devise a way for the wireless tag to transmit data so that the reader can identify which reader the data is being transmitted to. However, this approach requires the wireless tag to have increasingly sophisticated functions, which makes the wireless tag's configuration more complex. Therefore, it has been desired to prevent erroneous reception of transmission data from a wireless tag intended for another reader, without complicating the configuration of the wireless tag. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-112987 A Summary of the Invention [Problem to be solved by the invention]

[0004] The problem that the present invention aims to solve is to provide a communication device and a communication method that can prevent erroneous reception of transmission data from a wireless tag intended for another reader without complicating the configuration of the wireless tag. [Means for solving the problem]

[0005] The communication device of the embodiment includes a quadrature modulation unit, a transmission unit, a reception unit, a quadrature detection unit, a first demodulation unit, a first decoding unit, a second demodulation unit, a second decoding unit, a generation unit, a comparison unit, and a processing unit. The quadrature modulation unit quadrature-modulates a carrier wave using a first I signal and a first Q signal, and outputs a modulated wave. The transmission unit wirelessly transmits the modulated signal output from the quadrature modulation unit. The reception unit receives a wireless signal that is amplitude shift keyed by backscattering the transmission wave from the transmission unit by a wireless tag, and outputs a received signal. The quadrature detection unit detects the received signal output from the reception unit using the carrier wave, and outputs a second I signal and a second Q signal. The first demodulation unit detects at least one of the second I signal and the second Q signal output from the quadrature detection unit, and demodulates the first data that is amplitude shift keyed and transmitted from the wireless tag. The first decoding unit decodes the first data demodulated by the first demodulation unit. The second demodulation unit detects the second I signal and the second Q signal output from the quadrature detection unit and demodulates the frequency shift keyed second data. The second decoding unit decodes the second data demodulated by the second demodulation unit. The generation unit generates the first I signal and the first Q signal as signals for frequency shift keying the carrier wave with predetermined modulation data and inputs them to the quadrature modulation unit. The comparison unit compares the second data decoded by the second decoding unit with the modulated data. The processing unit executes data processing on the first data decoded by the second decoding unit when the comparison unit confirms that the second data decoded by the second decoding unit matches the modulated data. [Brief description of the drawings]

[0006] [Figure 1] FIG. 2 is a block diagram showing a main circuit configuration of a reading device according to an embodiment. [Diagram 2] 2 is a diagram showing waveforms of various signals related to transmission and reception of the reading device shown in FIG. 1. [Diagram 3] 2 is a diagram for explaining tag data reception processing in the reader shown in FIG. 1; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, an example of an embodiment will be described with reference to the drawings. FIG. 1 is a block diagram showing the main circuit configuration of a reading device 100 according to this embodiment.

[0008] The reader 100 reads data stored in an RFID (radio frequency identification) tag 200 from the RFID tag 200 by backscatter communication. That is, the reader 100 has a function as a communication device that performs wireless communication with the RFID tag 200 when reading data from the RFID tag 200. The reading device 100 includes an oscillator 1, a DA (digital to analog) converter 2, a quadrature modulator 3, a balun 4, a SAW (surface acoustic wave) filter 5, a power amplifier 6, an antenna duplexer 7, an antenna 8, a balun 9, a quadrature detector 10, an HPF (high pass filter) 11, two VGAs (variable gain amplifiers) 12, an AD (analog to digital) converter 13, a baseband processor 14, a CPU (central processing unit) 15, and a memory 16.

[0009] The oscillator 1 generates a predetermined frequency f local A sine wave of is generated as the carrier wave. The DA converter 2 converts two systems of signals (hereinafter referred to as a transmission I signal and a transmission Q signal) output in a digital state from the baseband processor 14 into analog signals. The quadrature modulator 3 inputs the transmission I signal and transmission Q signal analogized by the DA converter 2 as modulated waves. The quadrature modulator 3 inputs the carrier generated by the oscillator 1 and the carrier obtained by shifting the phase of the carrier by 90° as carrier waves of the I system and the Q system, respectively. The quadrature modulator 3 obtains a transmission signal by quadrature modulation. In this embodiment, a device having a well-known configuration including a phase shifter, two mixers, and an adder is used as the quadrature modulator 3. However, another well-known device having a different configuration may be used. For example, the quadrature modulator 3 may not include a phase shifter, and a carrier obtained by shifting the phase of the carrier output from the oscillator 1 by 90° using a phase shifter provided outside the quadrature modulator 3 may be input to the quadrature modulator 3 separately from the carrier output from the oscillator 1. The transmission I signal and the transmission Q signal correspond to a first I signal and a first Q signal, and the quadrature modulator 3 is an example of a modulation unit.

[0010] The balun 4 converts the balanced signal output from the quadrature modulator 3 into an unbalanced signal. The SAW filter 5 removes low and high frequency components from the transmission signal output from the balun 4 in order to limit unwanted emissions. The power amplifier 6 amplifies the power of the transmission signal that has passed through the SAW filter 5 to a level suitable for wireless transmission.

[0011] The antenna duplexer 7 supplies the transmission signal output from the power amplifier 6 to an antenna 8. The antenna duplexer 7 outputs the reception signal received by the antenna 8 to a balun 9. The antenna 8 emits radio waves corresponding to the transmission signal supplied via the antenna duplexer 7. The antenna 8 receives the incoming radio waves. That is, when a reflected wave from the RFID 200 arrives, the antenna 8 receives a signal corresponding to the reflected wave.

[0012] As described above, the transmission signal is wirelessly transmitted by the SAW filter 5, the power amplifier 6, and the antenna 8. That is, a transmitting section that wirelessly transmits a modulated wave output from the quadrature modulator 3 serving as a modulating section is configured by the SAW filter 5, the power amplifier 6, and the antenna 8. The antenna 8 also functions as a receiving section that receives a signal corresponding to a reflected wave that is an amplitude shift keying (ASK) wave transmitted by backscattering from the RFID tag 200, which is a wireless tag.

[0013] The balun 9 converts the unbalanced signal input via the antenna duplexer 7 into a balanced signal. The quadrature detector 10 performs quadrature detection on the received signal output from the balun 9 using a carrier generated by the oscillator 1 and a carrier obtained by shifting the phase of the carrier by 90°. The quadrature detector 10 outputs two systems of signals (hereinafter referred to as a received I signal and a received Q signal) obtained by quadrature detection in parallel. In this embodiment, a device having a well-known configuration including a distributor, a phase shifter, and two mixers is used as the quadrature detector 10. However, another well-known device having a different configuration may be used. For example, the quadrature detector 10 may not include a phase shifter, and a carrier obtained by shifting the phase of the carrier output from the oscillator 1 by 90° using a phase shifter provided outside the quadrature modulator 3 may be input to the quadrature modulator 3 separately from the carrier output from the oscillator 1. The quadrature detector 10 is an example of a quadrature detection unit, and the received I signal and the received Q signal correspond to a second I signal and a second Q signal.

[0014] The HPF 11 is a filter that filters a predetermined cutoff frequency f cut The HPF 11 passes components having a higher frequency than the input signal. The HPF 11 includes, for example, two DC (direct current) cut capacitors corresponding to the received I signal and the received Q signal, respectively. The HPF 11 corresponds to a filter section. The two VGAs 12 amplify the received I signal and the received Q signal that have passed through the HPF 11 to a level suitable for detection and data decoding, which will be described later. These two VGAs constitute an amplifier section. The AD converter 13 digitizes each of the received I signal and the received Q signal amplified by the VGA 12 .

[0015] The baseband processor 14 executes information processing for signal processing related to the baseband signal. The baseband processor 14 includes a signal generating function 141, an ASK demodulating function 142, an ASK decoding function 143, a limit amplifying function 144, an FSK demodulating function 145, an FSK decoding function 146, and a data comparing function 147 as functions realized by executing the information processing. The signal generating function 141 generates a transmission I signal and a transmission Q signal for frequency shift keying (FSK) with predetermined modulation data (hereinafter referred to as FSK modulation data) by the quadrature modulator 3 under the instruction of the CPU 15, and provides the signals in parallel to the DA converter 2. The ASK demodulating function 142 obtains an ASK demodulated signal by demodulating the ASK modulated signal included in the reception signal input to the quadrature detector 10 based on the reception I signal and reception Q signal output from the AD converter 13. The ASK decoding function 143 decodes the ASK demodulated signal and obtains the data transmitted from the RFID tag 200. The limit amplification function 144 performs limit amplification on each of the received I signal and the received Q signal output from the AD converter 13. The FSK demodulation function 145 obtains an FSK demodulated signal by demodulating the FSK modulated signal included in the received signal input to the quadrature detector 10 based on the received I signal and the received Q signal amplified by the limit amplification function 144. The FSK decoding function 146 decodes the FSK demodulated signal to obtain FSK decoded data. When the FSK decoded data obtained by the FSK demodulation function 145 matches the FSK modulated data, the data comparison function 147 outputs the data decoded by the ASK decoding function 143 to the CPU 15 as valid received data. The data decoded by the ASK decoding function 143 corresponds to the first data, and the FSK decoded data corresponds to the second data. Thus, the baseband processor 14 functions as a generation unit through signal generation function 141, as a first demodulation unit through ASK demodulation function 142, as a first decoding unit through ASK decoding function 143, as an amplification unit through limit amplification function 144, as a second demodulation unit through FSK demodulation function 145, as a second decoding unit through FSK decoding function 146, and as a comparison unit through data comparison function 147.

[0016] When communicating with the RFID tag 200, the CPU 15 controls the baseband processor 14 to output a transmission I signal and a transmission Q signal according to a predetermined sequence. The CPU 15 performs predetermined data processing on data decoded by the baseband processor 14. That is, when the data comparison function 147 confirms that the FSK modulated data matches the FSK decoded data, the CPU 15 executes data processing on the data decoded by the ASK decoding function, and is an example of a processing unit. The memory 16 stores an information processing program describing information processing to be executed by the CPU 15. The memory 16 stores various data required for the CPU 15 to execute various information processing. The memory 16 stores various data generated or acquired when the CPU 15 executes various information processing.

[0017] Next, the operation of the reading device 100 configured as above will be described. The operation of the reader 100 differs from that of known readers in terms of communication with the RFID tag 200 in the operation during the period when data is received from the RFID tag 200. Therefore, in the following, this operation will be described in detail, and descriptions of other known operations will be omitted.

[0018] When it is time to start reading data from the RFID tag 200, the CPU 15 instructs the baseband processor 14 to start reading. In response to this instruction, the baseband processor 14 starts generating and outputting, by the signal generating function 141, a transmission I signal and a transmission Q signal so that the transmission signal output by the quadrature modulator 3 becomes a required modulated wave.

[0019] The baseband processor 14 receives the frequency f local The baseband processor 14 generates a transmission I signal and a transmission Q signal so that a transmission signal obtained by FSKing a carrier wave of the frequency f with FSK modulation data, which is predetermined modulation data, is output from the quadrature modulator 3. Specifically, the baseband processor 14 generates the transmission I signal and the transmission Q signal by local +f dev and frequency is f local -f dev The baseband processor 14 generates a signal having a pattern based on FSK modulation data as a transmission signal, for example, by changing the frequency of the transmission I signal and the transmission Q signal to f dev By making the phase difference between the transmission I signal and the transmission Q signal different, the carrier wave is given +f dev or -f dev This produces a frequency shift of f dev may be arbitrarily determined by, for example, the designer of the reading device 100. However, the frequency f dev is the frequency f cut Higher than.

[0020] The FSK modulated data may be arbitrarily determined by, for example, the designer of the reading device 100. In this embodiment, the FSK modulated data is data consisting of a repetition of "10110101", and when the data is "1", the frequency of the unit period is f local +f dev When the data is "0", the frequency of the unit period is f local -f devIn addition, when the communication ranges of the multiple readers 100 overlap and there is a possibility that one RFID tag 200 is located within the overlapping range, the FSK modulated data is determined so as to be different for each of the multiple readers 100. Therefore, the FSK modulated data is identification data for identifying the reader 100 that has transmitted the transmission signal.

[0021] FIG. 2 is a diagram showing waveforms of various signals related to transmission and reception of the reader 100. In FIG. Waveform WA is the waveform of the carrier wave output by oscillator 1. Waveform WB is the waveform of a signal FSK'd with identification data. Waveform WC is the waveform of a reflected wave from RFID tag 200. However, Figure 2 shows an image of the increase and decrease in frequency of each signal, and the frequency relationship between waveform WA and waveforms WB and WC does not accurately represent the actual frequency relationship.

[0022] When the RFID tag 200 receives a transmission signal from the reader 100, it changes its reflectance according to the data to be read by the reader 100 (hereinafter referred to as tag data). As a result, the reflected wave from the RFID tag 200 is a signal obtained by ASKing the transmission signal from the reader 100 with the tag data. In other words, if the transmitted signal has a waveform WB, the reflected wave will have a waveform WC. Note that the 1-bit period of the reflected wave from the RFID tag 200 is Tb, and f dev >1 / Tb. When the transmission bit rate of the RFID tag 200 is slow, cut > 1 / Tb, so f dev >f cut >1 / Tb.

[0023] FIG. 3 is a diagram for explaining the tag data reception process in the reader 100. As shown in FIG. It is assumed that a received signal with a waveform WC shown in FIG. 2 is subjected to quadrature detection by the quadrature detector 10 to obtain a received I signal with a waveform WD and a received Q signal with a waveform WE shown in FIG. The frequencies of these received I and Q signals are f devand the cutoff frequency f cut Therefore, the received I signal and the received Q signal pass through the HPF 11.

[0024] In the baseband processor 14, when the received I signal and received Q signal that have passed through the HPF 11, been amplified by the VGA 12, and digitized by the AD converter 13 are input, the ASK demodulation function 142 detects and demodulates them. dev The components are removed to obtain a baseband signal corresponding to the tag data. The baseband processor 14 then decodes the tag data DAA from the demodulation result using the ASK decoding function 143. The process for this decoding may be the same as that performed in, for example, another existing reader.

[0025] When the baseband processor 14 receives the received I signal and the received Q signal digitized by the AD converter 13, the baseband processor 14 performs limit amplification using the limit amplification function 144. That is, the baseband processor 14 amplifies the received I signal and the received Q signal while limiting the maximum amplitude value in order to eliminate amplitude fluctuations caused by ASK modulation in the received I signal and the received Q signal and to equalize the amplitudes. Waveforms WF and WG in FIG. 2 represent waveforms after limit amplification of the received I signal and the received Q signal of the waveforms WD and WE.

[0026] A phase shift occurs between the received I signal and the received Q signal after the limit amplification according to the frequency of the reflected wave from the RFID tag 200. The received I signal and the received Q signal are detected by the FSK demodulation function 145 and demodulated as FSK-modulated I signal and Q signal, thereby obtaining an FSK-modulated baseband waveform. The FSK-modulated baseband waveform is then decoded by the FSK decoding function to obtain the identification data DAB contained in the reflected wave from the RFID tag 200 by FSK modulation. Note that when a reflected wave based on a transmission signal from another reader that does not have the function of transmitting a transmission signal FSK-modulated with identification data is received, the baseband processor 14 cannot decode the identification data.

[0027] When the identification data DAB decoded by the ASK decoding function 143 using the FSK demodulation function 145 matches the identification data corresponding to the transmission I signal and the transmission Q signal generated by the signal generation function 141, the baseband processor 14 outputs the tag data DAA decoded by the ASK decoding function 143 to the CPU 15. When the decoded identification data does not match the transmitted identification data or when the baseband processor 14 cannot decode the identification data, it discards the tag data DAA decoded by the ASK decoding function 143 as invalid. However, there is a time lag between when the signal generating function 141 starts outputting the transmission I signal and the transmission Q signal and when the FSK modulated signal based on the transmission data is sent as the transmission signal and when the RFID tag 200 starts transmitting the reflected wave, and part of the transmission data is not included in the reflected wave. Therefore, the data comparing function 147 does not compare the part of the identification data that was transmitted within a certain period from the start of transmission with the generated data.

[0028] When the tag data is provided from the baseband processor 14, the CPU 15 executes predetermined data processing on the tag data. This data processing is, for example, processing to add a product code included in the tag data to a product list. However, the content of the data processing may be arbitrarily determined by, for example, the designer or user of the reader 100. Thus, the reader 100 performs data processing only on tag data obtained from reflected waves from the RFID tag 200 based on a transmission signal transmitted by the reader 100 itself. Therefore, the reader 100 does not process tag data transmitted from the RFID tag 200 to another reader 100. In other words, the reader 100 does not erroneously receive tag data transmitted to another reader. In addition, since the RFID tag 200 does not need to perform special processing to identify which reader the response is for, it is possible to avoid the complexity of the configuration that would be required by adding a configuration for that purpose. For example, an existing device using a backscatter method can be used as the RFID tag 200 as is.

[0029] Furthermore, since the reading device 100 realizes FSK modulation and FSK demodulation through cooperation between the quadrature modulator 3, the quadrature detector 10, and the baseband processor 14, it is possible to realize the FSK modulation and FSK demodulation by simply changing the processing in the baseband processor 14 without changing the hardware configuration.

[0030] This embodiment can be modified in various ways as follows. In the above embodiment, the data used for FSK is data consisting of a repetition of a pattern of "1", "0", "1", "1", "0", "1", "0", and "1". However, the data used for FSK is not limited in any way. For example, data in which "0" or "1" occurs randomly may be used. For example, a pattern until the reception of the transmission data of the RFID tag 200 is completed may be determined in advance. If data in which "0" or "1" occurs randomly is used, the pattern is notified from the signal generation function 141 to the data comparison function 147. For example, the FSK modulation data generated by the signal generation function 141 may be stored in the built-in memory of the baseband processor 14, and the data comparison function 147 may refer to the data.

[0031] 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]

[0032] 1...oscillator, 2...DA converter, 3...quadrature modulator, 4, 9...balun, 5...SAW filter, 6...power amplifier, 7...antenna duplexer, 8...antenna, 9...balun, 10...quadrature detector, 13...AD converter, 14...baseband processor, 141...signal generation function, 142...ASK demodulation function, 143...ASK decoding function, 144...limit amplification function, 145...FSK demodulation function, 146...FSK decoding function, 147...data comparison function, 15...CPU, 16...memory, 100...reader, 200...RFID tag.

Claims

1. A communication device for communicating with a wireless tag, a quadrature modulation unit that quadrature-modulates a carrier wave using the first I signal and the first Q signal to output a modulated wave; a transmitter that wirelessly transmits the modulated wave output from the quadrature modulator; a receiving section which receives a radio signal that has been amplitude shift modulated by backscattering a transmission wave from the transmitting section by the wireless tag and outputs a received signal; a quadrature detection unit that detects the received signal output from the receiving unit using the carrier wave and outputs a second I signal and a second Q signal; a first demodulation unit that detects at least one of the second I signal and the second Q signal output from the quadrature detection unit and demodulates first data that is amplitude shift keyed and transmitted from the wireless tag; a first decoding unit that decodes the first data demodulated by the first demodulation unit; a second demodulation unit that detects the second I signal and the second Q signal output from the quadrature detection unit and demodulates second data that has been frequency shift keyed; a second decoding unit that decodes the second data demodulated by the second demodulation unit; a generator that generates the first I signal and the first Q signal as signals for frequency shift modulation of the carrier wave with predetermined modulation data, and inputs the first I signal and the first Q signal to the quadrature modulation unit; a comparison unit that compares the second data decoded by the second decoding unit with the modulated data; a processing unit that executes data processing on the first data decoded by the first decoding unit when the comparison unit confirms that the second data decoded by the second decoding unit matches the modulated data; A communication device equipped with the above.

2. a filter unit that passes frequency components higher than a cutoff frequency of the second I signal and the second Q signal output from the quadrature detection unit; an amplifier that amplifies the second I signal and the second Q signal that have passed through the filter; Further comprising: the generating unit generates the first I signal and the first Q signal so that a frequency shift amount of the frequency shift keying is greater than the cutoff frequency. The communication device according to claim 1 .

3. The generating unit generates the first I signal and the first Q signal so as to set the modulation data to predetermined data. The communication device according to claim 1 or 2.

4. The generating unit generates the first I signal and the first Q signal so as to make the modulation data random data. The communication device according to claim 1 or 2.

5. A method for communicating with a wireless tag, comprising: quadrature-modulating a carrier wave using the first I signal and the first Q signal to output a modulated wave; wirelessly transmitting the modulated wave; The wireless tag backscatters the transmitted wave by wireless transmission, receives an amplitude shift keyed wireless signal, and outputs the received signal; Detecting the received signal using the carrier wave and outputting a second I signal and a second Q signal; Detecting at least one of the second I signal and the second Q signal, and demodulating first data transmitted from the wireless tag through amplitude shift keying; Decoding the demodulated first data; Detecting the second I signal and the second Q signal and demodulating second data that has been frequency shift keyed; Decoding the demodulated second data; generating a first I signal and a first Q signal for frequency shift modulating the carrier wave with predetermined modulation data; comparing the decoded second data with the modulated data; performing data processing on the decoded first data when it is confirmed by the comparison that the decoded second data and the modulated data match each other; Communication methods.

Images