JP2008067318A - Radio tag communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide radio tag communication equipment capable of appropriately detecting a carrier wave or detecting a signal strength of a signal sneaked from a transmission side regarding cancel control thereof prior to communication. <P>SOLUTION: The radio tag communication equipment is equipped with: a first oscillation section 18 which oscillation-outputs a first frequency equal with a frequency of a carrier wave of a question wave Fc; a second oscillation section 20 which oscillation-outputs a second frequency different from the first frequency; a mixer 36 which performs detection on the basis of the first frequency or the second frequency; and a circuit switching section 50 which switches circuits so as to input the output from any one oscillation circuit of the first oscillation section 18 or of the second oscillation section 20 to the mixer 36. Thus, by separately using homodyne detection based on the first frequency and frequency conversion based on the second frequency in accordance with a target signal, various signals or the signal strength thereof can be suitably and appropriately detected. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement in a wireless tag communication device that performs communication with a wireless tag capable of wirelessly writing and reading information.

  2. Description of the Related Art An RFID (Radio Frequency Identification) system is known in which information is read out in a non-contact manner by a predetermined wireless tag communication device (interrogator) from a small wireless tag (responder) in which predetermined information is stored. This RFID system is capable of reading information stored in a wireless tag by communication with the wireless tag communication device even when the wireless tag is dirty or disposed at an invisible position. Therefore, practical use is expected in various fields such as merchandise management and inspection processes.

  As one aspect of such a wireless tag communication device, a device including a homodyne detection circuit (orthogonal detection circuit) for detecting a response wave returned from the wireless tag is known. For example, the wireless communication device described in Patent Document 1 is this. According to this technique, a response wave returned from the wireless tag can be suitably detected by a homodyne detection circuit which is a simple and practical frequency conversion circuit.

JP 2005-328382 A

  By the way, in information communication with the wireless tag by the wireless tag communication device, in order to avoid interference with other devices, carrier detection (carrier sense) is performed prior to the communication, and the communication channel is not used. It is necessary to confirm beforehand that it is in a state. Further, when a cancel circuit for suppressing a sneak signal from the transmission side is provided, it is conceivable to detect the signal strength of the sneak signal or the cancel signal from the transmission side. In the conventional technique as described above, the detection of the signal intensity related to the detection of the carrier wave and the cancellation control is performed using the homodyne detection circuit. However, when detecting the signal intensity related to the detection of the carrier wave and the cancel control using the homodyne detection circuit, it is necessary to detect the DC component of the signal, but detection of such a DC component is difficult to remove noise, There is a problem that it takes time to stabilize the signal, and there is a possibility that suitable detection cannot be performed. For this reason, there has been a demand for the development of a wireless tag communication device that can suitably detect the signal intensity related to the detection of the carrier wave prior to communication and the cancellation control of the sneak signal from the transmission side.

  The present invention has been made in the background of the above circumstances, and the object of the present invention is to suitably detect signal strength related to detection of a carrier wave prior to communication and control of canceling a sneak signal from a transmission side. An object of the present invention is to provide a wireless tag communication device that can be used.

  In order to achieve such an object, the gist of the present invention is that a query wave is transmitted from a transmitting antenna toward a radio tag, and a response wave returned from the radio tag according to the query wave is transmitted. A wireless tag communication device that communicates with the wireless tag by receiving it through a receiving antenna, and a first oscillation circuit that performs an oscillation output of a first frequency equal to the frequency of the carrier wave of the interrogation wave; A second oscillation circuit that performs oscillation output at a second frequency different from the first frequency, a frequency conversion circuit that performs detection based on the first frequency or the second frequency, and the first frequency And a circuit switching unit that switches a circuit so that an output from any one of the oscillation circuit and the second oscillation circuit is input to the frequency conversion circuit.

  According to this configuration, the first oscillation circuit that performs the oscillation output of the first frequency equal to the frequency of the carrier wave of the interrogation wave, and the second oscillation circuit that outputs the oscillation output of the second frequency different from the first frequency. Output from any one of the first oscillation circuit and the second oscillation circuit, the frequency conversion circuit that performs detection based on the first frequency or the second frequency, and the first oscillation circuit. A circuit switching unit that switches a circuit to be input to the frequency conversion circuit, so that homodyne detection based on the first frequency according to a signal of interest, and the second frequency By properly using the frequency conversion based on the above, various signals and their signal intensities can be detected appropriately and appropriately. That is, it is possible to provide a wireless tag communication device that can suitably detect the signal strength related to the detection of the carrier wave prior to the communication and the cancellation control of the sneak signal from the transmission side.

  Here, preferably, the output from the first oscillation circuit is used as a carrier wave of the interrogation wave. In this way, the configuration of the apparatus can be simplified.

  Preferably, a cancel circuit for outputting a cancel signal for suppressing a sneak signal from a transmission side included in a reception signal received by the reception antenna, a cancel signal output from the cancel circuit, and the A cancel signal combining unit configured to combine the received signal received by the receiving antenna; In this way, a sneak signal from the transmission side included in the received signal can be suppressed, and suitable communication with the wireless tag can be realized.

  Preferably, an amplification unit is provided in a signal transmission path between the receiving antenna and the frequency conversion circuit. In this way, it is possible to realize suitable communication with the wireless tag by amplifying the reception signal received by the reception antenna.

  Preferably, the amplifying unit is a variable amplifying unit capable of changing an amplification factor. In this way, when the signal strength of the cancel signal is detected, the signal strength can be suitably detected by setting the amplification factor of the variable amplification unit to 1.

  Preferably, a second circuit switching unit that switches between a signal transmission path that passes through the amplification unit and a signal transmission path that does not pass through the amplification unit is provided. In this way, when the signal strength of the cancel signal is detected, the signal strength can be suitably detected by using a circuit that does not pass through the amplification unit.

  Preferably, the second frequency is set so that the center frequency of the frequency band of the modulation signal included in the response wave from the wireless tag is the difference between the first frequency and the second frequency. It is a thing. In this way, the same band pass filter can be used for the homodyne detection output signal based on the first frequency and the output signal of the frequency conversion circuit determined based on the second frequency.

  Preferably, a band pass filter having a center frequency as a difference between the first frequency and the second frequency is provided. In this way, it is possible to extract a frequency band corresponding to the output signal of the frequency conversion circuit determined based on the second frequency. In addition, when the frequency band of the modulation signal included in the response wave from the wireless tag has a difference between the first frequency and the second frequency as a center frequency, the frequency band is based on the first frequency. The frequency band corresponding to the homodyne detection can be extracted together by the band pass filter.

  Preferably, in addition to the bandpass filter, a second bandpass filter corresponding to the frequency band of the modulation signal included in the response wave from the wireless tag is provided. According to this configuration, even if the center frequency of the frequency band of the modulation signal included in the response wave from the wireless tag deviates from the difference between the first frequency and the second frequency, And a frequency band corresponding to the output signal of the frequency conversion circuit determined based on the second frequency can be extracted.

  Preferably, the apparatus further comprises a signal strength detection unit for detecting the signal strength of the signal supplied from the frequency conversion circuit. In this way, it is possible to detect various signal strengths related to the sneak signal cancellation control from the transmission side.

  Preferably, a circuit switching control unit for controlling switching of the circuit by the circuit switching unit is provided, and the circuit switching control unit receives a response wave from the wireless tag from the first oscillation circuit. The circuit is switched so that the output is input to the frequency conversion circuit. In this way, when processing the response wave from the wireless tag, suitable communication with the wireless tag can be realized by performing homodyne detection based on the first frequency.

  Preferably, the circuit switching control unit outputs the output from the second oscillation circuit when detecting the signal strength of the sneak signal from the transmission side included in the reception signal received by the reception antenna. The circuit is switched so as to be input to the frequency conversion circuit. According to this configuration, when detecting the signal strength of the sneak signal from the transmission side, the signal strength of the output signal of the frequency conversion circuit determined based on the second frequency is measured, so that the signal of the sneak signal The intensity can be detected suitably.

  Preferably, the circuit switching control unit is configured so that the output from the second oscillation circuit is input to the frequency conversion circuit when detecting the signal strength of the cancellation signal output from the cancellation circuit. Is to switch. In this case, when detecting the signal strength of the cancel signal, the signal strength of the output signal of the frequency conversion circuit determined based on the second frequency is measured, so that the signal strength of the cancel signal is suitably adjusted. Can be detected.

  Preferably, the circuit switching control unit outputs the frequency conversion from the second oscillation circuit when detecting the signal strength of the received signal output from the cancel signal combining unit and the combined signal of the cancel signal. The circuit is switched so as to be input to the circuit. In this way, when detecting the signal strength of the combined signal of the received signal and the cancel signal, the combined signal is measured by measuring the signal strength of the output signal of the frequency conversion circuit determined based on the second frequency. The signal intensity can be suitably detected.

  Preferably, an oscillation circuit control unit for controlling the second oscillation circuit is provided, and the oscillation circuit control unit stops the operation of the second oscillation circuit when processing the response wave from the wireless tag. It is something to be made. In this way, when the response signal from the wireless tag is received, the oscillation signal component of the second oscillation circuit does not circulate as noise, and suitable communication with the wireless tag can be realized. .

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram illustrating a wireless tag communication system 10 to which the present invention is preferably applied. The RFID tag communication system 10 includes an RFID tag communication device 12 according to an embodiment of the present invention, and a single or plural (single in FIG. 1) RFID tags 14 that are communication targets of the RFID tag communication device 12. It is a so-called RFID (Radio Frequency Identification) system, and the RFID tag communication device 12 functions as an interrogator of the RFID system, and the RFID tag 14 functions as a responder. That is, when the interrogation wave F _c (transmission signal) is transmitted from the radio tag communication device 12 toward the radio tag 14, a predetermined command (transmission data) is received in the radio tag 14 that has received the interrogation wave F _c. As a result, the interrogation wave F _c is modulated and sent back to the RFID tag communication apparatus 12 as a response wave F _r (reply signal), so that information is transmitted between the RFID tag communication apparatus 12 and the RFID tag 14. Communication takes place. The wireless tag communication system 10 is used, for example, for managing articles in a predetermined communication area. The wireless tag 14 is preferably attached to an article to be managed, for example. And are provided integrally.

FIG. 2 is a diagram illustrating the configuration of the wireless tag communication device 12. As shown in FIG. 2, the wireless tag communication device 12 according to the present embodiment communicates with the wireless tag 14 in order to read and write information with respect to the wireless tag 14 and detect the direction of the wireless tag 14. A DSP (Digital Signal Processor) 16 for performing digital signal processing such as communication of information, outputting transmission data as a digital signal, demodulating a return signal from the wireless tag 14, and the transmission signal A first oscillating unit 18 which is a first oscillating circuit that performs an oscillating output of a first frequency corresponding to a carrier wave, and an oscillating output of a second frequency different from the frequency output from the first oscillating unit 18. A second oscillating unit 20 that is a second oscillating circuit to be performed, a transmission amplifier 22 that outputs the carrier wave output from the first oscillating unit 18 with the transmission data supplied from the DSP 16 being output, A transmitting antenna 24 for transmitting signals to be supplied as a question wave F _c from transmission amplifier 22, a receiving antenna 26 for receiving the reply wave F _r from the wireless tag 14, the receiving antenna 26, a cancel circuit 28 for outputting a cancel signal for suppressing a sneak signal from the transmission side included in the reception signal received by the reception signal 26, a cancellation signal output from the cancellation circuit 28, and the reception antenna 26. A cancel signal synthesizer 30 for synthesizing the received signal, a variable amplifier 32 for amplifying the signal output from the cancel signal synthesizer 30, and a predetermined frequency band among the signals output from the variable amplifier 32 A band pass filter (Band Pass Filter) 34 that passes only the first signal, and the first frequency or the second frequency. Only a signal in a predetermined frequency band among a mixer 36 as a frequency conversion circuit for detecting a signal supplied from the bandpass filter 34 based on the number and an I-phase signal (in-phase component) output from the mixer 36. An I-phase bandpass filter 38 that passes through the I-phase, an I-phase amplifier 40 that amplifies the signal supplied from the I-phase bandpass filter 38, and a signal supplied from the I-phase amplifier 40 is converted into a digital signal. An I-phase A / D converter 42 supplied to the DSP 16, a Q-phase bandpass filter 44 that passes only a signal in a predetermined frequency band among the Q-phase signals (orthogonal components) output from the mixer 36, A Q-phase amplifier 46 that amplifies the signal supplied from the Q-phase bandpass filter 44, and a signal supplied from the Q-phase amplifier 46 as a digital signal The Q-phase A / D converter 48 that converts the signal into the DSP 16 and supplies the signal to the DSP 16 and the output from one of the first oscillator 18 and the second oscillator 20 are input to the mixer 36. Thus, the circuit switching unit 50 that switches circuits is provided.

  The cancel circuit 28 includes a cancel amplitude control unit 52 that is a variable amplifier that amplifies the amplitude of the carrier wave supplied from the first oscillation unit 18, and a variable that controls the phase of the signal supplied from the cancel amplitude control unit 52. A cancel phase control unit 54 that is a phase shifter, and the amplitude and / or phase of the carrier wave supplied from the first oscillation unit 18 by the cancel amplitude control unit 52 and / or the cancel phase control unit 54. It is controlled and supplied to the cancel signal combining unit 30 as a cancel signal.

  The DSP 16 includes a CPU that is a central processing unit, a ROM that is a read-only memory, a RAM that is a read / write memory as needed, and a signal according to a program stored in advance in the ROM while using a temporary storage function of the RAM. This is a so-called microcomputer system that performs processing, and includes a transmission data generation unit 56, an oscillation circuit control unit 58, a circuit switching control unit 60, a cancel signal control unit 62, a signal intensity detection unit 64, and a variable amplification unit control unit 66. In preparation.

  The transmission data generation unit 56 generates transmission data for the wireless tag 14 and supplies the transmission data to the transmission amplifier 22. The transmission data is, for example, a predetermined command bit string, and the transmission amplifier 22 puts the transmission data supplied from the transmission data generation unit 56 on the carrier wave supplied from the first oscillation unit 18 and transmits the transmission data. Transmission is performed from the trusted antenna 24 toward the wireless tag 14.

The oscillation circuit control unit 58 selectively controls the oscillation output of the frequency by the first oscillation unit 18 and the second oscillation unit 20. That is, the operation (on / off) of the first oscillating unit 18 and the second oscillating unit 20 is controlled so that the oscillation output is performed from the first oscillating unit 18 and / or the second oscillating unit 20. Preferably, the operation of the second oscillating unit 20 is stopped when processing the response wave F _r from the wireless tag 14.

The circuit switching control unit 60 controls circuit switching by controlling the operation of the circuit switching unit 50. That is, the switching of the circuit is controlled so that the output from one of the first oscillating unit 18 and the second oscillating unit 20 is input to the mixer 36. The circuit switching control unit 60 connects the circuit switching unit 50 to either one of the terminals a and b shown in FIG. 2, so that the oscillation outputs from the first oscillation unit 18 and the second oscillation unit 20 are selectively transmitted. (The output from the first oscillation unit 18 at the terminal a and the output from the second oscillation unit 20 at the terminal b) are input to the mixer 36. Here, as shown in FIG. 2, the oscillation output from the first oscillating unit 18 is supplied to the transmission amplifier 22 regardless of the switching of the circuit switching unit 50 and is used as a carrier wave of the interrogation wave F _c. . Therefore, when the oscillation output from the first oscillation unit 18 is input to the mixer 36, homodyne detection is performed in the mixer 36, and the oscillation output from the second oscillation unit 20 is input to the mixer 36. In this case, the mixer 36 performs frequency conversion.

  The cancel signal control unit 62 controls the amplitude and / or phase of the cancel signal output from the cancel circuit 28. Specifically, the amplitude of the cancel signal is controlled by controlling the amplification factor in the cancel amplitude control unit 52, and the phase of the cancel signal is controlled by controlling the phase shift amount in the cancel phase control unit 54. . Preferably, the sneak signal from the transmission side received by the reception antenna 26 and the cancellation signal output from the cancellation circuit 28 have the same signal strength and opposite phase so that the amplitude and / or Or the phase is controlled. Preferably, the amplitude and / or phase of the cancel signal output from the cancel circuit 28 is controlled so that the signal strength of the received signal detected by the signal strength detector 64 is as small as possible.

  The signal strength detection unit 64 detects the signal strength of the signal supplied from the mixer 36. Preferably, based on the I-phase signal supplied from the I-phase A / D converter 42 and / or the Q-phase signal supplied from the Q-phase A / D converter 48, for example, the I-phase signal, the Q-phase The signal strength is detected by calculating the square root of the sum of the squares of the respective signals. By this signal strength detection unit 64, the signal strength of the reception signal received by the reception antenna 26, the signal strength of the sneak signal from the transmission side in the reception antenna 26, the cancel signal output from the cancel circuit 28 The signal strength, the received signal (wraparound signal) output from the cancel signal combining unit 30, the signal strength of the combined signal of the cancel signal, and the like are detected.

The variable amplification unit controller 66 controls the amplification factor of the variable amplification unit 32. Preferably, the amplification factor of the variable amplifying unit 32 is controlled in accordance with the type of signal to be detected by the signal intensity detecting unit 64. That is, the variable amplification unit 32 is used for processing the response wave F _r from the wireless tag 14, detecting the carrier of the surrounding wireless tag communication device, and detecting the signal strength of the combined signal output from the cancel signal combining unit 30. Is set to a predetermined amplification factor, while the signal strength of the sneak signal from the transmission side in the receiving antenna 26 and the signal strength of the cancel signal output from the cancel circuit 28 are detected. By making the amplification factor of the amplification unit 32 approximately 1, the amplification by the variable amplification unit 32 is prevented from being performed. Preferably, the variable amplifying unit 32 is controlled to be turned on / off, that is, to start / stop operation.

Here, the circuit switching control unit 60 is preferably configured so that the output from the first oscillating unit 18 is input to the mixer 36 when the response wave F _r from the wireless tag 14 is processed. The circuit is switched via the switching unit 50. In other words, when processing the response wave F _r from the wireless tag 14, a circuit is provided to supply the oscillation output of the first oscillation unit 18 to the mixer 36 so that homodyne detection is performed in the mixer 36. Switch.

  The circuit switching control unit 60 preferably detects the signal strength of the sneak signal from the transmission side included in the reception signal received by the reception antenna 26 in the signal strength detection unit 64. 2 The circuit is switched so that the output from the oscillator 20 is input to the mixer 36. In other words, when the signal strength of the sneak signal from the transmission side included in the reception signal received by the reception antenna 26 is detected, the mixer 36 performs the frequency conversion on the second signal. The circuit is switched to supply the oscillation output of the oscillation unit 20.

  In addition, the circuit switching control unit 60 preferably allows the output from the second oscillating unit 20 to be input to the mixer 36 when detecting the signal strength of the cancel signal output from the cancel circuit 28. Switch the circuit. In other words, when detecting the signal strength of the cancel signal output from the cancel circuit 28, the oscillation output of the second oscillating unit 20 is supplied to the mixer 36 so that the frequency conversion is performed in the mixer 36. Switch the circuit to.

  In addition, the circuit switching control unit 60 preferably uses the second oscillating unit 20 to detect the signal strength of the reception signal (wraparound signal) output from the cancel signal combining unit 30 and the combined signal of the cancel signal. The circuit is switched so that the output of is input to the mixer. In other words, the frequency conversion is performed in the mixer 36 when detecting the signal strength of the combined signal when controlling the cancel signal in order to make the combined signal of the received signal and the cancel signal as small as possible. The circuit is switched so that the oscillation output of the second oscillation unit 20 is supplied to the mixer 36.

FIG. 3 is a diagram illustrating the configuration of the RFID circuit element 72 provided in the RFID tag 14. As shown in FIG. 3, the RFID circuit element 72 processes an antenna unit 74 for transmitting / receiving signals to / from the RFID tag communication device 12 and a signal received by the antenna unit 74. And an IC circuit unit 76 for the purpose. The IC circuit unit 76 rectifies the interrogation wave F _c received from the RFID tag communication device 12 received by the antenna unit 74, and the energy of the interrogation wave F _c rectified by the rectification unit 78. Functions as a power supply unit 80 for accumulation, a clock extraction unit 82 that extracts a clock signal from the carrier wave received by the antenna unit 74 and supplies the clock signal to the control unit 88, and an information storage unit that can store a predetermined information signal The RFID circuit element 72 via the memory unit 84, the modulation / demodulation unit 86 that is connected to the antenna unit 74 and modulates and demodulates the signal, the rectification unit 78, the clock extraction unit 82, the modulation / demodulation unit 86, and the like. And a control unit 88 for controlling the operation of. The control unit 88 performs control to store the predetermined information in the memory unit 84 by communicating with the wireless tag communication device 12, and transmits the interrogation wave F _c received by the antenna unit 74 to the modulation / demodulation unit 86. in executing the basic control as a response wave F _r of the control or the like that reflects back from the antenna unit 74 in terms of modulated based on the information signal stored in the memory unit 84.

FIG. 4 is a diagram for explaining a signal used for information communication between the wireless tag communication device 12 and the wireless tag 14 and a modulation signal by the wireless tag 14. As shown in FIG. 4, the modulation signal included in the response wave F _r reflected back from the RFID circuit element 72, that is, the frequency band of the modulation signal in the modulation / demodulation unit 86 is preferably the first oscillation unit. The difference (= f ₁ −f ₂ ) between the first frequency f ₁ corresponding to the 18 oscillation outputs and the second frequency f ₂ corresponding to the oscillation output of the second oscillation unit 20 is the center frequency. . The I-phase bandpass filter 38 and the Q-phase bandpass filter 44 preferably both pass _a signal in _a frequency band fa having _a center frequency as a difference between the first frequency and the second frequency. As a result, the common band-pass filters 38 and 44 can be used for the homodyne detection based on the first frequency and the frequency conversion based on the second frequency in the mixer 36.

  FIG. 5 is a flowchart for explaining a main part of the RFID tag communication control by the DSP 16 of the RFID tag communication apparatus 12 and is repeatedly executed at a predetermined cycle.

  First, in step (hereinafter, step is omitted) S1, the circuit switching unit 50 is connected to the terminal b so that the output from the second oscillation unit 20 is input to the mixer 36. Next, in S2, the amplification factor of the variable amplification unit 32 (LNA) is set to a predetermined value so that the amplification factor of the variable amplification unit 32 is set large, and the oscillation output from the second oscillation unit 20 is output. The carrier detection that is started and detects the output signal of another RFID tag communication apparatus placed around is started. Next, in S3, it is determined whether or not the carrier detection is completed. While the determination of S3 is denied, the system waits by repeating the determination of S3. However, when the determination of S3 is affirmed, in S3A, other RFID tag communication devices placed around It is determined whether an output has been detected. If the determination in S3A is affirmative, it is determined in S3B that the other RFID tag communication apparatus is using a channel that the wireless tag communication device desires to use, and the first transmission circuit 18 and the first transmission circuit 18 are switched so as to switch the channel to be used. 2 After changing the output frequency of the transmission circuit 20, the processing from S3 is executed again. However, when the determination of SA3 is negative, the oscillation output by the first oscillation unit 18 is started in S4, Transmission of a carrier wave is started from the transmitting antenna 24. Next, in S5, the gain of the variable amplifying unit 32 is reduced so that the gain of the variable amplifying unit 32 is approximately 1, and the cancel signal amplitude control unit 52 is set so that the output of the cancel circuit is reduced. And the signal strength of the sneak signal from the transmission side included in the reception signal received by the reception antenna 26 in a state where the transmission amplifier 22 is activated and the carrier is transmitted from the transmission antenna 24 is detected. Done. Next, in S5A, in the state where the transmission amplifier 22 is stopped and the carrier transmitted from the transmission antenna 24 is made small, in S6, the cancel circuit 28 is kept with the gain of the variable amplification section 32 kept small. The cancel circuit 28 is adjusted so that the signal strength of the cancel signal output from the signal is substantially equal to that of the sneak signal detected in S5 and the phase is reversed. Next, in S6A, the transmission amplifier 22 is activated and a carrier is transmitted from the transmission antenna 24. In S7, the amplification factor of the variable amplification unit 32 is set to a predetermined value, and the variable amplification unit 32 is set. Is set, and the signal strength of the received signal (wraparound signal) output from the cancel signal combining unit 30 and the combined signal of the cancel signal is detected. Next, in S8, it is determined whether or not the cancel signal has converged, that is, whether or not the signal intensity of the synthesized signal output from the cancel signal synthesizing unit 30 has converged to a predetermined value or less. If the determination in S8 is negative, after the amplitude or phase of the output signal of the cancel circuit 28 is finely adjusted in S8A, the processes in and after S7 are repeated again, but the determination in S8 is affirmed. In this case, after the oscillation output from the second oscillation unit 20 is stopped in S8B, the output from the first oscillation unit 18 is input to the mixer 36 by the oscillation circuit control unit 58 in S9. Thus, the circuit switching unit 50 is connected to the terminal a. Next, in S10, the transmission data generated by the transmission data generation unit 56 is transmitted in a state where the amplification factor of the variable amplification unit 32 is set to a predetermined value, and information is transmitted between the wireless tag 14 and the information. After communication is performed and homodyne detection (orthogonal demodulation) and data interpretation of the reception signal received by the reception antenna 26 are performed, this routine is terminated. In the above control, S2, S3B, and S8B are operations of the oscillation circuit control unit 58, S1 and S9 are operations of the circuit switching control unit 60, and S5, S8, and S8A are operations of the cancel signal control unit 62. S2, S5, S6, S7, and S10 correspond to the operations of the signal intensity detection unit 64 and the variable amplification unit control unit 66, respectively.

Thus, according to the present embodiment, the first oscillating unit 18 that is the first oscillating circuit that performs the oscillation output of the first frequency equal to the carrier frequency of the interrogation wave F _c , and the first frequency thereof. A second oscillation unit 20 that is a second oscillation circuit that performs oscillation output of a second frequency different from the above, and a mixer 36 as a frequency conversion circuit that performs detection based on the first frequency or the second frequency; And a circuit switching unit 50 that switches a circuit so that an output from any one of the first oscillation unit 18 and the second oscillation unit 20 is input to the mixer 36. Thus, by properly using homodyne detection based on the first frequency and frequency conversion based on the second frequency according to the signal of interest, various signals and their signal strengths can be detected appropriately and appropriately. it can. That is, it is possible to provide the RFID tag communication device 12 that can suitably detect the signal strength related to the detection of the carrier wave prior to the communication and the cancellation control of the sneak signal from the transmission side.

Further, since the output from the first oscillating unit 18 is used as the carrier wave of the interrogation wave F _c , the configuration of the apparatus can be simplified.

  The cancel circuit 28 outputs a cancel signal for suppressing a sneak signal from the transmission side included in the received signal received by the receiving antenna 26, the cancel signal output from the cancel circuit 28, and the reception Since the cancel signal combining unit 30 for combining the reception signal received by the antenna 26 is provided, the sneak signal from the transmission side included in the reception signal can be suppressed, and the wireless tag 14 A suitable communication can be realized.

  In addition, since the variable amplifying unit 32 is provided in the signal transmission path between the receiving antenna 26 and the mixer 36, the radio tag is amplified by amplifying the received signal received by the receiving antenna 26. Communication with the network 14 can be realized.

  Further, since the variable amplification unit 32 is a variable gain amplifier that can change the amplification factor, when the signal strength of the cancel signal is detected, the amplification factor of the variable amplification unit 32 is set to 1. The signal intensity can be detected suitably.

In addition, the frequency band of the modulation signal included in the response wave F _r from the wireless tag 14 has a difference between the first frequency and the second frequency as a center frequency, so the first frequency The same bandpass filters 38 and 44 can be used for the homodyne detection based on the above and the frequency conversion based on the second frequency.

  In addition, since bandpass filters 38 and 44 having a center frequency as a difference between the first frequency and the second frequency are provided, extraction of a frequency band corresponding to frequency conversion based on the second frequency is performed. In addition, the bandpass filters 38 and 44 can extract the frequency band corresponding to the homodyne detection based on the first frequency.

  Further, since the signal strength detection unit 64 (S2, S5, S6, S7, and S10) for detecting the signal strength of the signal supplied from the mixer 36 is provided, the sneak signal from the transmission side is detected. Various signal intensities relating to cancel control can be detected.

The circuit switching control unit 60 (S1 and S9) that controls switching of the circuit by the circuit switching unit 50 is provided, and the circuit switching control unit 60 performs the processing of the response wave F _r from the wireless tag 14. Since the circuit is switched so that the output from the first oscillating unit 18 is input to the mixer 36, homodyne detection based on the first frequency is performed when processing the response wave F _r from the wireless tag 14. By doing so, it is possible to realize suitable communication with the wireless tag 14.

  The circuit switching control unit 60 outputs the output from the second oscillating unit 20 to the mixer 36 when detecting the signal strength of the sneak signal from the transmission side included in the reception signal received by the reception antenna 26. Therefore, when detecting the signal strength of the sneak signal from the transmission side, the signal strength of the sneak signal is preferably obtained by performing frequency conversion based on the second frequency. Can be detected.

  The circuit switching control unit 60 switches the circuit so that the output from the second oscillation unit 20 is input to the mixer 36 when detecting the signal strength of the cancel signal output from the cancellation circuit 28. Therefore, when detecting the signal strength of the cancel signal, the signal strength of the cancel signal can be suitably detected by performing frequency conversion based on the second frequency.

  The circuit switching control unit 60 inputs the output from the second oscillating unit 20 to the mixer 36 when detecting the signal strength of the received signal output from the cancel signal combining unit 30 and the combined signal of the cancel signal. Therefore, when detecting the signal strength of the combined signal of the received signal and the cancel signal, the signal strength of the combined signal is preferably obtained by performing frequency conversion based on the second frequency. Can be detected.

The oscillation circuit control unit 58 (S2, S3B, and S8B) stops the second oscillation circuit 20 when processing the response wave F _r from the wireless tag 14, so that the wireless tag 14 The generation of noise by the second oscillation circuit 20 can be suitably suppressed when the response wave F _r is processed.

  Next, another preferred embodiment of the present invention will be described in detail with reference to the drawings. In the following description, parts common to the embodiments are denoted by the same reference numerals and description thereof is omitted.

  FIG. 6 is a diagram for explaining the configuration of a wireless tag communication device 90 according to another embodiment of the present invention that is preferably used in the wireless tag communication system 10. As shown in FIG. 6, the RFID tag communication apparatus 90 according to the present embodiment has a second I-phase that allows only a signal in a predetermined frequency band among I-phase signals (in-phase components) output from the mixer 36 to pass. A band-pass filter 38 ', a second I-phase amplifier 40' for amplifying a signal supplied from the I-phase band-pass filter 38 ', and a signal supplied from the I-phase amplifier 40' as a digital signal A second I-phase A / D converter 42 'that converts and supplies the signal to the DSP 16, and a second signal that passes only a signal in a predetermined frequency band among Q-phase signals (orthogonal components) output from the mixer 36. Q-phase bandpass filter 44 ', a second Q-phase amplifier 46' for amplifying a signal supplied from the Q-phase bandpass filter 44 ', and a signal supplied from the Q-phase amplifier 46' Digital signal And a conversion to a second Q-phase A / D converter 48 is supplied to the DSP 16 ', and is configured to include.

The I-phase bandpass filter 38 ′ and Q-phase bandpass filter 44 ′ are filters corresponding to different frequency bands from the I-phase bandpass filter 38 and Q-phase bandpass filter 44 described above. The frequency band that the filter 38 ′ and the Q-phase bandpass filter 44 ′ pass corresponds to the frequency band of the modulation signal included in the response wave F _r from the wireless tag 14. Further, in the RFID tag communication system 10 that performs communication by the RFID tag communication apparatus 90 having such a configuration, the frequency band of the modulation signal included in the response wave F _r from the RFID tag 14 is not necessarily the first frequency and the first frequency. The difference from the frequency of 2 may not be the center frequency.

Thus, according to this embodiment, wherein apart from the band-pass filter 38,44, second bandpass filter 38 which corresponds to the frequency band of the modulation signal included in the response wave F _r from the wireless tag 14 ′, 44 ′, the center frequency of the frequency band of the modulation signal included in the response wave F _r from the wireless tag 14 deviates from the difference between the first frequency and the second frequency. Even in this case, it is possible to extract the frequency band corresponding to the homodyne detection based on the first frequency and the frequency conversion based on the second frequency.

  FIG. 7 is a diagram for explaining the configuration of a wireless tag communication device 92 that is still another embodiment of the present invention and is preferably used in the wireless tag communication system 10. As shown in FIG. 7, the RFID tag communication apparatus 92 according to the present embodiment includes an amplification unit 94 having a fixed amplification factor between the reception antenna 26 and the mixer 36 as an alternative to the variable amplification unit 32. In the signal transmission path. Further, a second circuit switching unit 96 that switches between a signal transmission path that passes through the amplification unit 94 and a signal transmission path that does not pass through the amplification unit 94 is provided. A second circuit switching control unit 98 that controls switching is provided. When the second circuit switching control unit 98 connects the circuit switching unit 96 to any one of the terminals a and b shown in FIG. 7, the signal transmission path via the amplification unit 94 and the amplification unit are not passed. A signal transmission path is selectively established (a path that passes through terminal a and a path that does not pass through terminal b).

  Thus, according to the present embodiment, the second circuit switching unit 96 that switches between the signal transmission path that passes through the amplification unit 94 and the signal transmission path that does not pass through the amplification unit 94 is provided. When detecting the signal strength of the cancel signal, the signal strength can be suitably detected by using a circuit that does not pass through the amplifier 94.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, in the above-described embodiment, the oscillation circuit control unit 58, the circuit switching control unit 60, the cancel signal control unit 62, the signal strength detection unit 64, and the like are all functionally provided in the DSP 16. However, the present invention is not limited to this, and control devices having these control functions may be individually provided. In addition, these controls may be digital signal processing or analog signal processing.

  In the above-described embodiment, the transmission antenna 24 for transmitting a transmission signal toward the wireless tag 14 and the reception for receiving a reply signal returned from the wireless tag 14 according to the transmission signal. The wireless tag communication device 12 and the like provided with the antennas 26 for each have been described. However, a transmission signal is transmitted toward the wireless tag 14 and is returned from the wireless tag 14 according to the transmission signal. The present invention is also preferably applied to a wireless tag communication device provided with an antenna for transmission and reception for receiving a reply signal. The present invention is also suitably applied to a wireless tag communication device that includes a plurality of transmission antennas and / or reception antennas and selectively and / or uses them.

  In addition, although not illustrated one by one, the present invention is implemented with various modifications within a range not departing from the gist thereof.

It is a figure explaining the radio | wireless tag communication system to which this invention is applied suitably. It is a figure explaining the structure of the RFID tag communication apparatus which is one Example of this invention. It is a figure explaining the structure of the RFID circuit element with which the RFID tag which is a communication object of the RFID tag communication apparatus of FIG. 2 was equipped. It is a figure explaining the signal used for the information communication between the wireless tag communication apparatus of FIG. 2 and the wireless tag of FIG. 3, and the modulation signal by the wireless tag. 3 is a flowchart illustrating a main part of RFID tag communication control by a DSP of the RFID tag communication apparatus of FIG. 2. It is a figure explaining the structure of the RFID tag communication apparatus which is the other Example of this invention. It is a figure explaining the structure of the radio | wireless tag communication apparatus which is another Example of this invention.

Explanation of symbols

12, 90, 92: RFID tag communication device 14: RFID tag 18: first oscillation unit (first oscillation circuit)
20: 2nd oscillation part (2nd oscillation circuit)
24: Transmission antenna 26: Reception antenna 28: Cancel circuit 30: Cancel signal synthesis unit 32: Variable amplification unit 36: Mixer (frequency conversion circuit)
38: I-phase bandpass filter 38 ': Second I-phase bandpass filter 44: Q-phase bandpass filter 44': Second Q-phase bandpass filter 50: Circuit switching unit 60: Circuit switching control unit 64: Signal Intensity detector 94: amplifier 96: second circuit switching unit

Claims (15)

The interrogation wave is transmitted from the transmitting antenna toward the radio tag, and the response wave returned from the radio tag according to the interrogation wave is received by the receiving antenna, thereby communicating with the radio tag. A wireless tag communication device,
A first oscillation circuit for generating an oscillation output of a first frequency equal to the frequency of the carrier wave of the interrogation wave;
A second oscillation circuit for performing oscillation output at a second frequency different from the first frequency;
A frequency conversion circuit that converts a frequency based on the first frequency or the second frequency;
A circuit switching unit that switches a circuit so that an output from any one of the first oscillation circuit and the second oscillation circuit is input to the frequency conversion circuit. A wireless tag communication device.   2. The wireless tag communication device according to claim 1, wherein an output from the first oscillation circuit is used as a carrier wave of the interrogation wave. A cancel circuit for outputting a cancel signal for suppressing a sneak signal from a transmission side included in a reception signal received by the reception antenna;
3. The wireless tag communication device according to claim 1, further comprising: a cancel signal combining unit that combines a cancel signal output from the cancel circuit and a reception signal received by the reception antenna.   4. The RFID tag communication apparatus according to claim 1, wherein an amplifier is provided in a signal transmission path between the receiving antenna and the frequency conversion circuit.   The wireless tag communication device according to claim 4, wherein the amplifying unit is a variable amplifying unit capable of changing an amplification factor.   6. The wireless tag communication device according to claim 4, further comprising a second circuit switching unit that switches between a signal transmission path that passes through the amplification unit and a signal transmission path that does not pass through the amplification unit.   The second frequency is set such that a center frequency of a frequency band of a modulation signal included in a response wave from the wireless tag is a difference between the first frequency and the second frequency. The RFID tag communication device according to any one of 1 to 6.   The RFID tag communication apparatus according to any one of claims 1 to 7, further comprising a band pass filter having a difference between the first frequency and the second frequency as a center frequency.   9. The wireless tag communication device according to claim 8, further comprising a second bandpass filter corresponding to a frequency band of a modulation signal included in a response wave from the wireless tag, separately from the bandpass filter.   The wireless tag communication device according to claim 1, further comprising a signal strength detection unit for detecting a signal strength of a signal supplied from the frequency conversion circuit.   A circuit switching control unit for controlling switching of the circuit by the circuit switching unit, wherein the circuit switching control unit outputs an output from the first oscillation circuit when the response wave from the wireless tag is processed; The wireless tag communication device according to claim 1, wherein the circuit is switched so as to be input to the wireless tag communication device.   The circuit switching control unit inputs an output from the second oscillation circuit to the frequency conversion circuit when detecting the signal strength of the sneak signal from the transmission side included in the reception signal received by the reception antenna. The wireless tag communication device according to claim 11, wherein the circuit is switched so that the circuit is switched.   The circuit switching control unit switches the circuit so that the output from the second oscillation circuit is input to the frequency conversion circuit when detecting the signal strength of the cancellation signal output from the cancellation circuit. Item 15. The wireless tag communication device according to Item 11 or 12.   The circuit switching control unit is configured to input the output from the second oscillation circuit to the frequency conversion circuit when detecting the signal strength of the combined signal of the reception signal and the cancellation signal output from the cancel signal combining unit. The wireless tag communication device according to claim 11, wherein the circuit is switched to the other.   An oscillation circuit control unit that controls the second oscillation circuit is provided, and the oscillation circuit control unit stops the operation of the second oscillation circuit when processing a response wave from the wireless tag. The wireless tag communication device according to any one of 1 to 14.

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