JP5137128B2 - RFID reader / writer - Google Patents

Description

  The present invention relates to an RFID reader / writer that performs wireless communication with a mobile information communication body such as an IC tag, and more particularly to an RFID reader / writer that performs communication with an IC tag having a different communication frequency.

  A wireless system using an RFID reader / writer that performs wireless communication with an IC tag is generally called an RFID (Radio Frequency Identification) system, and an IC tag (in addition to an RF tag, an RFID tag) in which ID information and various data are written. Tags and wireless tags), and electromagnetic waves can be used to read or write information from a remote location, making it practical for use in various fields such as distribution, transportation, and medical care. Yes.

  Since there are various usage forms in such an RFID system using an IC tag, IC tags and RFID reader / writers having different specifications are used depending on purposes. For example, there are a wide range of radio frequency bands used, such as a microwave band of 2.45 GHz, a UHF band of 950 MHz, or 13.56 MHz used in an electromagnetic induction system. Therefore, communication with these IC tags having different communication frequencies requires a plurality of RFID reader / writers corresponding to the respective communication frequencies.

  However, from the standpoint of introducing and operating an RFID system, installing and installing a plurality of RFID readers / writers corresponding to each communication frequency is a large cost, which is a major obstacle to the spread of the RFID system. It is a factor.

  In view of such a situation, many proposals have been made on technologies related to an RFID system that can be handled by a single RFID reader / writer for IC tags having different communication frequencies.

  FIG. 3 is a block diagram showing an example of the configuration of a conventional RFID reader / writer. A conventional RFID reader / writer 300 includes a transmission unit 304 including a plurality of transmission units 302 and a plurality of reception units corresponding to each communication frequency in order to communicate with IC tags (not shown) having different communication frequencies. A receiving unit 305 including 303 is provided. Each transmission unit 302 includes an oscillator 307, an amplification circuit 308, a modulation circuit 309, and the like, and each reception unit 303 includes an amplification circuit 308, a demodulation circuit 310, and the like. Each transmission unit 302 and each reception unit 303 are connected to a transmission antenna 311 and a reception antenna 312 for transmitting and receiving radio signals.

  The baseband signal generated by the control unit 301 is transmitted to the transmission unit 302 having the communication frequency selected by the transmission / reception signal switching unit 306, and transmitted from the transmission antenna 311 through the amplification circuit 308 and the modulation circuit 309. In addition, a radio signal received by the receiving antenna 312 as a response from the IC tag is sent to the receiving unit 303, passed through the amplifier circuit 308 and the demodulator circuit 310, and sent to the control unit 301 via the transmission / reception signal switching unit 306.

  3 illustrates the case where there are two types of communication frequencies. However, when three or more types of communication frequencies are used, in addition to this, the transmission unit 302 and the reception unit 303 are respectively connected to the transmission unit 304 and It is necessary to add and connect to the receiving unit 305 in parallel.

  As described above, the RFID reader / writer is configured with at least a transmission unit including a transmission / reception antenna, an oscillator and a modulation / amplification circuit, a reception unit including an amplification / demodulation circuit, and the like. A technique for performing multiplex communication with IC tags having different communication frequencies by switching to a transmission unit and a reception unit of a communication frequency is disclosed in Patent Document 1, for example.

  Further, Patent Document 2 discloses a technique that enables communication with a single RFID reader / writer with respect to IC tags having a simpler configuration and different communication frequencies. According to this technology, even when different communication frequencies are used, an RFID reader / writer having a configuration that applies a common modulation scheme and encoding scheme is used. And it can be made low-cost.

JP 2002-15288 A JP 2006-229433 A

  However, in the prior art described in Patent Document 1, as described above, a hardware configuration corresponding to each communication frequency, that is, a transmission / reception unit including an oscillator and a modulation / demodulation circuit corresponding to each communication frequency must be provided in parallel. As a result, there is a problem that the circuit scale increases, and the RFID reader / writer becomes complicated and expensive.

  On the other hand, in Patent Document 2, as described above, an RFID reader / writer having a simpler circuit configuration can be realized by providing the RFID reader / writer with a configuration using a common modulation scheme and encoding scheme. .

  However, in the prior art described in Patent Document 2, only the basic circuit configuration of the RFID reader / writer is referred to, and an amplifier circuit or a mixer (for example, corresponding to each communication frequency) required for actual design is required. No mention is made of mixers).

  In general, an RFID system radiates electromagnetic waves, which may interfere with other wireless systems. In order to avoid this, the electromagnetic wave used in the RFID system needs to be strictly adapted to the radio wave standard of each communication frequency. For this purpose, in the signal processing circuit of the RFID reader / writer, an unnecessary wave suppression filter for suppressing unnecessary waves generated in the propagation path of the circuit, that is, unnecessary components caused by distortion or interference between the circuits is added. Is indispensable, but Patent Document 2 does not make detailed reference to this.

  That is, in an actual RFID reader / writer circuit design, in addition to the conventional configuration circuit described in Patent Document 2, it is necessary to provide an amplifier circuit, a mixer, an unnecessary wave suppression filter, and the like corresponding to each communication frequency. As a result, there is a problem that the difficulty of circuit design increases and the circuit scale also increases.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to realize a low-cost RFID with a simple configuration capable of communicating with an IC tag having a different communication frequency with a single RFID reader / writer. It is to provide a reader / writer.

  As a result of various studies, the present inventors have found the following means for solving the above problems. That is, in a wireless system using an RFID tag / writer that is an interrogator and an IC tag that is a transponder having at least an IC chip and an antenna that performs radio communication at different communication frequencies, that is, an RFID system, the RFID reader / writer is , A power supply for supplying power to the IC tag by radio and transmitting at least a radio signal; a reception antenna for receiving the radio signal; a transmission circuit for performing signal processing of the transmission signal; It is composed of a receiving circuit that performs signal processing of a signal and a control unit that has at least an internal CPU and controls the entire RFID reader / writer, and can communicate with IC tags having different communication frequencies with one RFID reader / writer. It is possible.

  In order to perform wireless communication between an IC tag having a different communication frequency and one RFID reader / writer, the RFID reader / writer according to the present invention includes a transmission unit, that is, at least the control unit, the transmission circuit, and the transmission antenna. A plurality of signal paths of the circuit unit, that is, a plurality of paths (hereinafter referred to as transmission signal paths) until the baseband signal generated by the control unit is transmitted from the transmission antenna via the transmission circuit are provided. The transmission antenna is preferably connected to each of the paths, and each of the transmission antennas preferably transmits a radio signal having a different communication frequency.

  The transmission unit is provided with means for electrically switching the transmission signal path, that is, a first switch for switching to the transmission signal path selected by the control unit between the transmission circuit and the plurality of transmission antennas. It is good. Furthermore, it is preferable that at least one of the transmission signal paths includes a first mixer and a first unnecessary wave suppression filter. Further, it is preferable that a first local oscillator is connected to the transmission circuit, and a second local oscillator is connected to the first mixer.

  In order to generate a transmission signal having a different communication frequency in the transmission unit, for example, a transmission signal having a first communication frequency may be generated using a first local oscillator. The generated transmission signal of the first communication frequency is preferably transmitted wirelessly from the first transmission antenna connected to the first transmission signal path.

  For example, the transmission signal of the second communication frequency is generated by performing frequency conversion on the transmission signal of the first communication frequency using the second local oscillator and the first mixer. Is good. The generated transmission signal of the second communication frequency is an unnecessary wave, that is, the first unnecessary wave suppression filter for suppressing an unnecessary component caused by distortion or interference between circuits in a transmission signal propagation path. The second transmission antenna connected to the second transmission signal path is preferably transmitted wirelessly via the.

  Furthermore, the RFID reader / writer according to the present invention is configured such that a signal path of a circuit unit including a receiving unit, that is, at least the control unit, the receiving circuit, and the receiving antenna, that is, a radio signal received by the receiving antenna is the receiving circuit. A plurality of paths (hereinafter referred to as reception signal paths) to reach the control unit via the connection, the reception antennas are connected to each of the plurality of reception signal paths, and each of the reception antennas has a different communication It is preferable to receive a radio signal of a frequency.

  The receiving unit is provided with means for electrically switching the received signal path, that is, a second switch for switching to the received signal path selected by the control unit between the receiving circuit and the plurality of receiving antennas. It is good. Furthermore, it is preferable that at least one of the reception signal paths includes a second mixer and a second unnecessary wave suppression filter. The second local oscillator may be connected to the second mixer.

  In order to process reception signals of different communication frequencies at the reception unit, for example, a radio signal of the first communication frequency may be received by a first reception antenna connected to the first reception signal path. .

  Further, for example, a radio signal of the second communication frequency is received by the second reception antenna connected to the second reception signal path, and passes through the second unnecessary wave suppression filter connected thereto. The second mixer and the second local oscillator are preferably used for conversion to the first communication frequency and sent to the control unit.

  In addition to the circuit configuration described above, the RFID reader / writer according to the present invention individually connects the reception antenna or the transmission antenna to each of the plurality of transmission signal paths or the plurality of reception signal paths. Instead, a single transmission antenna may be connected to the plurality of transmission signal paths, and a single reception antenna may be connected to the plurality of reception signal paths.

  That is, in addition to the configuration circuit of the reception unit and the transmission unit described above, a third switch and a fourth switch are connected to each of the front stage of the single transmission antenna and the rear stage of the single reception antenna, A circuit configuration for switching between the plurality of transmission signal paths and the plurality of reception signal paths may be employed. Thereby, the quantity of a transmission antenna and a receiving antenna can be suppressed.

That is, according to the present invention, for different IC tag whose communication frequencies, performs power supply by radio, and the two transmit antennas which performs transmission of at least the radio signals, and two receive antennas for receiving the radio signal A transmission circuit, a reception circuit, a control unit, a first switch, a second switch, a first mixer, a second mixer, a first local oscillator, and a second local oscillator The control unit is connected to the transmission circuit and the reception circuit, the first local oscillator is connected to the transmission circuit, the two transmission signal paths are respectively connected to the two transmission antennas, wherein said first switches and the transmitter circuit by arranging the enable switch the connection to the two transmit signal path, one of the transmit signal path between the transmitting circuit and the two transmission signal path, before E Bei only the first mixer and the first unnecessary wave suppression filter, said the first mixer is connected a second local oscillator, and the other transmit signal path, directly connected to the other transmission antenna The frequency of the signal transmitted from the one transmission antenna matches the frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator, and is transmitted from the other transmission antenna. The frequency of the signal matches the frequency of the first local oscillator, and the receiving circuit and the second switch are connected, and the two received signal paths are respectively connected to the two receiving antennas, and switchable to connect to the said reception circuit by disposing the second switch two receive signal path between the said reception circuit two receive signal path, one of the received signals The road, the second mixer and e Bei only the second unnecessary wave suppression filter, said the second mixer is connected the second local oscillator, the other of the received signal path, the other received The frequency of the signal directly connected to the antenna and received from the one receiving antenna matches the frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator, and the other receiving signal is received. An RFID reader / writer is obtained in which the frequency of the signal received from the antenna matches the frequency of the first local oscillator .

According to the present invention, power is supplied wirelessly to IC tags having different communication frequencies, and at least a transmission antenna that transmits a radio signal, a reception antenna that receives the radio signal, a transmission circuit, A receiving circuit, a control unit, a first switch, a second switch, a third switch, a fourth switch, a first mixer, a second mixer, and a first local oscillator; A second local oscillator, the control unit is connected to the transmission circuit and the reception circuit, the first local oscillator is connected to the transmission circuit, the transmission circuit and the two transmission signal paths By arranging the first switch between the transmission antenna and the two transmission signal paths, the third switch is arranged between the transmission circuit and the transmission antenna. Connection to signal path And switchable, one transmission signal path, the first mixer and e Bei only the first unnecessary wave suppression filter, said the first mixer is connected a second local oscillator, transmission other The signal path is directly connected to the third switch, and the frequency of the signal transmitted from the one transmission antenna is a frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator. And the frequency of the signal transmitted from the other transmitting antenna matches the frequency of the first local oscillator, and the second signal is transmitted between the receiving circuit and the two received signal paths. arranged switches, by disposing the fourth switch between the two receive signal path and the reception antenna, cut the connection to the two receive signal path between the receiving antenna and the receiving circuit E possible and then, one of the receive signal path, said second mixer and e Bei only the second unnecessary wave suppression filter, said the second mixer the second local oscillator is connected to the other of the receiving The signal path is directly connected to the fourth switch, and the frequency of the signal received via the one received signal path is the frequency of the first local oscillator and the frequency of the second local oscillator. Thus, an RFID reader / writer is obtained in which the frequency of the signal received through the other received signal path matches the frequency of the first local oscillator .

  As described above, according to the present invention, even when communicating with an IC tag having a different communication frequency with one RFID reader / writer, a hardware configuration corresponding to each communication frequency, that is, each communication frequency is set. It is not necessary to provide a transmission / reception unit comprising a corresponding oscillator and modulation / demodulation circuit in parallel, and as described above, a plurality of transmission signal paths and a plurality of reception signal paths are provided for each of the transmitter and receiver of the RFID reader / writer. And at least one of the plurality of transmission signal paths and the plurality of reception signal paths, a mixer to which a local oscillator is connected and an unnecessary wave suppression filter are provided, so that the RFID reader / writer The effect of reducing the circuit scale can be obtained. As a result, it is possible to communicate with an IC tag having a different communication frequency with a single RFID reader / writer, and it is possible to provide a low-cost RFID reader / writer with a simple configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a first embodiment of an RFID reader / writer according to the present invention. FIG. 1 illustrates a case where two types of communication frequencies, that is, the first communication frequency f1 and the second communication frequency f2 can be handled.

  The RFID reader / writer 100 according to the first embodiment of the present invention includes at least a control unit 101, a transmission unit, and a reception unit. The transmission unit includes a transmission circuit 102, a first local oscillator 104, and a first switch. 106, a first mixer 110, a second local oscillator 105, a first unwanted wave suppression filter 112, a first transmission antenna 114, and a second transmission antenna 115, and the reception unit includes a reception circuit 103, It comprises a second switch 107, a second mixer 111, a second local oscillator 105, a second unwanted wave suppression filter 113, a first reception antenna 116, and a second reception antenna 117. However, the second local oscillator 105 is connected to both the first mixer 110 of the transmission unit and the second mixer 111 of the reception unit.

  The control unit 101 has at least an internal CPU and the like, and is connected to the transmission unit and the reception unit, and controls the entire RFID reader / writer 100.

  The first switch 106 switches between the first transmission signal path and the second transmission signal path, and the second switch 107 switches between the first reception signal path and the second reception signal path.

  The first transmission signal path is formed by connecting the control unit 101, the transmission circuit 102, the first switch 106, and the first transmission antenna 114 connected to one of the branch points of the first switch 106. The second transmission signal path is a control unit 101, a transmission circuit 102, a first switch 106, a first mixer 110 connected to one of the branch points of the first switch 106, This is a line formed by connecting one unnecessary wave suppression filter 112 and the second transmission antenna 115. A second local oscillator 105 is connected to the first mixer 110.

  The first reception signal path is formed by connecting the control unit 101, the reception circuit 103, the second switch 107, and the first reception antenna 116 connected to one of the branch points of the second switch 107. The second reception signal path is a control unit 101, a reception circuit 103, a second switch 107, a second mixer 111 connected to one of the branch points of the second switch 107, This is a line formed by connecting the second unwanted wave suppression filter 113 and the second receiving antenna 117. A second local oscillator 105 is connected to the second mixer 111.

  The first transmission antenna 114 and the first reception antenna 116 are responsible for transmission and reception of radio signals of the first communication frequency f1, and the second transmission antenna 115 and the second reception antenna 117 are second communication frequency f2. It is responsible for sending and receiving radio signals.

  The RFID reader / writer 100 configured as described above communicates with two types of IC tags (not shown) having different communication frequencies by the following signal flow.

  First, a case where communication is performed with the IC tag at the first communication frequency f1 will be described. The baseband signal generated by the control unit 101 is sent to the transmission circuit 102, modulated, amplified and band-limited to the first communication frequency f1 using the first local oscillator 104 connected thereto, The transmission signal of the communication frequency f1. At the same time, the first switch 106 switches the branch point so as to select the first transmission signal path, that is, to be connected to the first transmission antenna 114, based on the command signal from the control unit 101.

  The transmission signal of the first communication frequency f1 is transmitted from the first transmission antenna 114 through the first transmission signal path. At the same time, the power for driving the IC chip provided in the IC tag corresponding to the first communication frequency f1 is transmitted from the first transmitting antenna 114 wirelessly.

  When the RFID reader / writer 100 receives a response from the IC tag corresponding to the first communication frequency f1, the second switch 107 selects the first reception signal path by the command signal from the control unit 101. In other words, the branch point is switched so as to be connected to the first receiving antenna 116, and the first receiving antenna 116 receives the radio signal from the IC tag. The received reception signal of the first communication frequency f 1 is amplified and demodulated via the reception circuit 103 and sent to the control unit 101.

  As described above, when the RFID reader / writer 100 of the present invention communicates with the IC tag at the first communication frequency f1, that is, the transmission / reception signal of the first communication frequency f1 is the first transmission signal path and the first reception. The signal processing in the case of passing through the signal path is the same as that in the case of the conventional RFID reader / writer except for the first switch 106 and the second switch 107.

  Next, a case where communication is performed with the IC tag at the second communication frequency f2 will be described. As in the case of communicating with the IC tag at the first communication frequency f1 described above, the baseband signal generated by the control unit 101 is sent to the transmission circuit 102, and the first local oscillator 104 connected thereto is sent through the first local oscillator 104. The first communication frequency f1 is used to modulate, amplify and band-limit, and a transmission signal of the first communication frequency f1 is obtained. At the same time, the first switch 106 switches the branch point so as to select the second transmission signal path, that is, to be connected to the second transmission antenna 115, based on the command signal from the control unit 101.

  The transmission signal of the first communication frequency f1 is sent to the first mixer 110 in the second transmission signal path, and frequency-mixed using the second local oscillator 105 connected to the first mixer 110. Further, unnecessary components are removed through the first unnecessary wave suppression filter 112 to become a transmission signal of the second communication frequency f 2 and transmitted from the second transmission antenna 115. At the same time, the power for driving the IC chip provided in the IC tag corresponding to the second communication frequency f2 is transmitted from the second transmission antenna 115 wirelessly. However, the first unwanted wave suppression filter 112 in the second transmission signal path is designed to comply with the radio wave standard of the second communication frequency f2.

  When the RFID reader / writer 100 receives a response from the IC tag corresponding to the second communication frequency f2, the second switch 107 selects the second reception signal path by the command signal from the control unit 101. In other words, the branch point is switched so as to connect to the second receiving antenna 117, and the second receiving antenna 117 receives the radio signal from the IC tag. The received reception signal of the second communication frequency f2 is sent to the second mixer 111 through the second unnecessary wave suppression filter 113 in the second reception signal path, and is connected to the second mixer 111. Frequency mixing is performed using the second local oscillator 105 thus generated, and a received signal having the first communication frequency f1 is obtained. The received signal of the first communication frequency f 1 that has been frequency-converted from the received signal of the second communication frequency f 2 is amplified and demodulated via the receiving circuit 103 and sent to the control unit 101.

  As described above, the RFID reader / writer according to the present invention is a mixer based on a switch with respect to the circuit configuration of the RFID reader / writer designed to communicate with the IC tag only at one kind of communication frequency, that is, the first communication frequency. By simply adding a new line including a frequency converter composed of a local oscillator, an unnecessary wave suppression filter, and a transmission or reception antenna, communication at a second communication frequency corresponding to this is also possible.

  That is, the most part of the circuit related to transmission / reception corresponding to the first communication frequency of the RFID reader / writer is used as it is, and the circuit part related to the second communication frequency is newly added without changing the circuit design drastically. It's okay. Accordingly, it is possible to provide an RFID reader / writer that has a simple configuration and is low in cost and that is compatible with two types of communication frequencies.

(Second Embodiment)
FIG. 2 is a block diagram showing the configuration of the second embodiment of the RFID reader / writer of the present invention. FIG. 2 illustrates a case where two types of communication frequencies, that is, the first communication frequency f1 and the second communication frequency f2 can be handled.

  The RFID reader / writer 200 according to the second embodiment of the present invention includes at least a control unit 201, a transmission unit, and a reception unit. The transmission unit includes a transmission circuit 202, a first local oscillator 204, and a first switch. 206, the first mixer 210, the second local oscillator 205, the first unnecessary wave suppression filter 212, the third switch 208, and the third transmission antenna 214, and the reception unit includes the reception circuit 203, the first It includes a second switch 207, a second mixer 211, a second local oscillator 205, a second unnecessary wave suppression filter 213, a fourth switch 209, and a third reception antenna 216. However, the second local oscillator 205 is connected to both the first mixer 210 of the transmission unit and the second mixer 211 of the reception unit.

  The control unit 201 has at least a CPU or the like inside, is connected to the transmission unit and the reception unit, and performs overall control of the RFID reader / writer 200.

  The first switch 206 and the third switch 208 perform switching between the first transmission signal path and the second transmission signal path, and the second switch 207 and the fourth switch 209 perform the first reception signal path. And the second received signal path is switched.

  The first transmission signal path includes a control unit 201, a transmission circuit 202, a first switch 206, a third switch 208 connected to one of the branch points of the first switch 206, and the third switch A line formed by connecting a third transmission antenna 214 connected to one of the branch points of the switch 208, and a second transmission signal path includes a control unit 201, a transmission circuit 202, a first switch 206, One of the branch points of the first switch 210 connected to one of the branch points of the first switch 206, the first unwanted wave suppression filter 212, the third switch 208, and the third switch 208. This is a line formed by connecting a third transmission antenna 214 connected to. In addition, a second local oscillator 205 is connected to the first mixer 210.

  The first reception signal path includes a control unit 201, a reception circuit 203, a second switch 207, a fourth switch 209 connected to one of the branch points of the second switch 207, and the fourth switch. A line formed by connecting a third reception antenna 216 connected to one of the branch points of the switch 209, and a second reception signal path includes a control unit 201, a reception circuit 203, a second switch 207, One of the branch points of the second mixer 211 connected to one of the branch points of the second switch 207, the second unwanted wave suppression filter 213, the fourth switch 209, and the fourth switch 209. This is a line formed by connecting a third receiving antenna 216 connected to. A second local oscillator 205 is connected to the second mixer 211.

  The third transmission antenna 214 transmits both radio signals of the first communication frequency f1 and the second communication frequency f2, and the third reception antenna 216 transmits the first communication frequency f1 and the second communication frequency. A dual-frequency shared transmission antenna and a dual-frequency receive antenna that are responsible for receiving both radio signals of frequency f2.

  The RFID reader / writer 200 configured as described above communicates with two types of IC tags (not shown) having different communication frequencies in the following signal flow.

  First, a case where communication is performed with the IC tag at the first communication frequency f1 will be described. The baseband signal generated by the control unit 201 is sent to the transmission circuit 202, modulated, amplified and band-limited to the first communication frequency f1 using the first local oscillator 204 connected thereto, The transmission signal of the communication frequency f1. At the same time, the first switch 206 and the third switch 208 switch the branch point so as to select the first transmission signal path by the command signal from the control unit 201.

  The transmission signal of the first communication frequency f1 is transmitted from the third transmission antenna 214 through the first transmission signal path. At the same time, the power for driving the IC chip provided in the IC tag corresponding to the first communication frequency f1 is transmitted from the third transmission antenna 214 wirelessly.

  In addition, when the RFID reader / writer 200 receives a response from the IC tag corresponding to the first communication frequency f1, the second switch 207 and the fourth switch 209 receive the first signal from the control unit 201 according to the command signal. The branch point is switched so that the received signal path is selected, and the third receiving antenna 216 receives the radio signal from the IC tag. The received reception signal of the first communication frequency f 1 is amplified and demodulated via the reception circuit 203 and sent to the control unit 201.

  Next, a case where communication is performed with the IC tag at the second communication frequency f2 will be described. As in the case of communicating with the IC tag at the first communication frequency f1 described above, the baseband signal generated by the control unit 201 is sent to the transmission circuit 202, and the first local oscillator 204 connected thereto is transmitted. The first communication frequency f1 is used to modulate, amplify and band-limit, and a transmission signal of the first communication frequency f1 is obtained. At the same time, the first switch 206 and the third switch 208 switch the branch point so as to select the second transmission signal path by the command signal from the control unit 201.

  The transmission signal of the first communication frequency f1 is sent to the first mixer 210 in the second transmission signal path, and is frequency-mixed using the second local oscillator 205 connected to the first mixer 210. Further, unnecessary components are removed through the first unnecessary wave suppression filter 212 to become a transmission signal of the second communication frequency f 2 and transmitted from the third transmission antenna 214. At the same time, the power for driving the IC chip provided in the IC tag corresponding to the second communication frequency f2 is transmitted from the third transmission antenna 214 wirelessly. However, the first unnecessary wave suppression filter 212 in the second transmission signal path is designed to comply with the radio wave standard of the second communication frequency f2.

  In addition, when the RFID reader / writer 200 receives a response from the IC tag corresponding to the second communication frequency f2, the second switch 207 and the fourth switch 209 receive the second signal by the command signal from the control unit 201. The branch point is switched so that the received signal path is selected, and the third receiving antenna 216 receives the radio signal from the IC tag. The received reception signal of the second communication frequency f2 is sent to the second mixer 211 through the second unnecessary wave suppression filter 213 in the second reception signal path and connected to the second mixer 211. Frequency mixing is performed using the second local oscillator 205 thus generated, and a received signal having the first communication frequency f1 is obtained. The received signal of the first communication frequency f 1 that has been frequency-converted from the received signal of the second communication frequency f 2 is amplified and demodulated via the receiving circuit 203 and sent to the control unit 201.

  As described above, the RFID reader / writer according to the second embodiment of the present invention uses a transmission antenna and a reception antenna as dual-frequency antennas, so that a single transmission antenna or a single reception antenna has different communication frequencies. Communication with the IC tag is enabled. Due to the effect of reducing the number of antennas, an RFID reader / writer having a simpler configuration can be realized.

  Further, when operating an RFID system corresponding to three or more types of communication frequencies, the number of branches of the RFID reader / writer switch shown in the first and second embodiments of the present invention is increased, and transmission and reception signal paths Newly added, and each additional transmission and reception signal path is equipped with a frequency converter consisting of a mixer and a local oscillator, an unwanted wave suppression filter, a transmission or reception antenna, etc. Needless to say.

  Hereinafter, an example in which communication is performed with two types of IC tags having different communication frequencies using the RFID reader / writer exemplified in the first embodiment will be described with reference to FIG.

(Example)
The RFID reader / writer 100 uses two types of communication frequencies, that is, the first communication frequency f1 as f1 = 953 MHz in the 950 MHz band which is the UHF band, and the microwave communication band f2 = 2 as the second communication frequency f2. It communicates wirelessly with an IC tag (not shown) compatible with .45 GHz.

  The oscillation frequency f0 of the first local oscillator 104 connected to the transmission circuit 102 is f0 = 953 MHz. Circuit elements constituting the transmission circuit 102, for example, a mixer, an amplifier, a filter, etc. (all not shown) are optimized for the 950 MHz band, and the transmission circuit 102 has a radio frequency standard for the 950 MHz band. Satisfies the requirements. Similarly, circuit elements constituting the receiving circuit 103, for example, a mixer, an amplifier, a filter, etc. (all not shown) are optimized for the 950 MHz band, and the receiving circuit 103 has a frequency of 950 MHz. Satisfies the requirements of the radio standard of the band.

  The transmission signal having the first communication frequency f1 = 953 MHz is obtained by modulating, amplifying, and band-limiting the baseband signal generated by the control unit 101 using the oscillation signal having the oscillation frequency f0 = 953 MHz of the first local oscillator 104. And output from the transmission circuit 102. Next, the first switch 106 switches the transmission signal path to the first transmission signal path, and the transmission signal having the first communication frequency f1 = 953 MHz passes through the first transmission signal path and passes through the first transmission signal path. It is transmitted from the antenna 114 by radio.

  When the RFID reader / writer 100 receives a response from the IC tag, a radio signal having a first communication frequency f1 = 953 MHz transmitted from the IC tag is received by the first receiving antenna 116, and the first communication is performed. The received signal has a frequency f1 = 953 MHz. Next, the second switch 107 switches the reception signal path to the first reception signal path, and the reception signal having the first communication frequency f1 = 953 MHz passes through the first reception signal path and passes through the reception circuit 103. Via the control unit 101.

  On the other hand, the transmission signal of the second communication frequency f2 = 2.45 GHz is transmitted from the transmission circuit 102 to the transmission signal of the first communication frequency f1 = 953 MHz and the second signal connected to the first mixer 110. An oscillation signal having an oscillation frequency fd = 1487 MHz of the local oscillator 105 is frequency-mixed by the first mixer 110, and the transmission signal output from the first mixer 110 is passed through the first unwanted wave suppression filter 112. Is obtained after

  That is, the first switch 106 switches the transmission signal path to the second transmission signal path, and the transmission signal having the first communication frequency f1 = 953 MHz is transmitted along the second transmission signal path along the first mixer. 110 is input. At this time, since the oscillation frequency fd of the second local oscillator 105 is 1487 MHz, f1 + fd = 953 MHz + 1487 MHz = 2440 MHz, and a transmission signal output of fm = 2440 MHz is obtained from the first mixer 110. Further, the transmission signal of fm = 2440 MHz passes through the first unnecessary wave suppression filter 112 to suppress unnecessary components such as image frequency and harmonics, and transmission of the second communication frequency f2 = 2.45 GHz. Signal. The transmission signal having the second communication frequency f2 = 2.45 GHz is transmitted from the second transmission antenna 115 by radio.

  However, of the radio frequency band used in the RFID system, the radio frequency standard of 2.45 GHz, which is a microwave band, is less stringent than the communication frequency of the 950 MHz band, which is a UHF band. Therefore, since the transmission signal of the first communication frequency f1 = 953 MHz subjected to strict band limitation in advance is frequency-converted into the transmission signal of the second communication frequency f2 = 2.45 GHz, the first frequency after the frequency mixing is performed. By simply passing the output from one mixer 110 through the first unwanted wave suppression filter 112, that is, only suppressing the image frequency and harmonics, the radio wave standard of the communication frequency of 2.45 GHz can be sufficiently satisfied. .

  When the RFID reader / writer 100 receives a response from the IC tag, a radio signal having a second communication frequency f2 = 2.45 GHz transmitted from the IC tag is received by the second receiving antenna 117, The received signal has a communication frequency f2 = 2.45 GHz. Next, the second switch 107 switches the received signal path to the second received signal path, and the received signal having the second communication frequency f2 = 2.45 GHz is changed along the second received signal path to the second received signal path. Through the unnecessary wave suppression filter 113, the received signal becomes fm = 2440 MHz, and is input to the second mixer 111. At this time, since the oscillation frequency fd of the second local oscillator 105 is 1487 MHz, fm−fd = 2440 MHz−1487 MHz = 953 MHz, and the first communication frequency converted from the second communication frequency f2 = 2.45 GHz. A reception signal output of f1 = 953 MHz is obtained from the second mixer 111. The frequency-converted received signal having the first communication frequency f 1 = 953 MHz is sent to the control unit 101 via the receiving circuit 103.

  The IC tag used in this example is of a label type having a dipole transmission / reception antenna and an IC chip formed by printing a copper foil on a base material, and having adhesiveness on the back surface of the base material. Each is affixed to an arbitrary part of a plurality of articles (not shown). An IC tag corresponding to the first communication frequency f1 = 953 MHz is attached to half of the plurality of articles, and an IC tag corresponding to the second communication frequency f2 = 2.45 GHz is attached to the other half. Affixed.

  The first transmission antenna 114 and the second transmission antenna 115 of the RFID reader / writer 100, and the first reception antenna 116 and the second reception antenna 117 are arranged at a gate (not shown) through which an article passes. . When an arbitrary article passes through the gate, the IC tag attached to the arbitrary article receives a radio signal transmitted from the first transmission antenna 114 or the second transmission antenna 115 of the RFID reader / writer 100. Then, the IC tag responding to this returns a radio signal to the first receiving antenna 116 or the second receiving antenna 117 of the RFID reader / writer 100 arranged at the gate. At this time, the internal circuit of the RFID reader / writer 100 switches the first switch 106 and the second switch 107 by a command signal from the control unit 101, selects a signal path of a corresponding communication frequency, and performs signal processing.

  Under the above-mentioned conditions, an arbitrary article was selected from a plurality of articles to which the IC tag was attached and passed between the gates. At this time, the control unit 101 of the RFID reader / writer 100 has recognized that the IC tag that has passed through the gate corresponds to the first communication frequency f1 = 953 MHz. The internal circuit of the RFID reader / writer 100 switches the first switch 106 and the second switch 107 in response to a command signal from the control unit 101, the first transmission signal path corresponding to the first communication frequency f1 = 953 MHz, and the first switch. One received signal path was selected for signal processing. At this time, the RFID reader / writer 100 and the IC tag communicated without any problem.

  Subsequently, an arbitrary article was selected from a plurality of articles to which the IC tag was attached, and passed between the gates. At this time, the control unit 101 of the RFID reader / writer 100 has recognized that the IC tag that has passed through the gate corresponds to the second communication frequency f2 = 2.45 GHz. The internal circuit of the RFID reader / writer 100 switches the first switch 106 and the second switch 107 by a command signal from the control unit 101, and a second transmission signal path corresponding to the second communication frequency f2 = 2.45 GHz. And the second received signal path was selected for signal processing. At this time, the RFID reader / writer 100 and the IC tag communicated without any problem.

  The embodiments of the present invention have been described above using the embodiments. However, the present invention is not limited to the embodiments, and the present invention is not limited to the scope of the present invention. Included in the invention. That is, various changes and modifications that can be naturally made by those skilled in the art are also included in the present invention.

1 is a block diagram showing a configuration of a first embodiment of an RFID reader / writer according to the present invention. The block diagram which shows the structure of 2nd Embodiment of the RFID reader-writer of this invention. The block diagram which shows an example of a structure of the conventional RFID reader / writer.

Explanation of symbols

100, 200, 300 RFID reader / writer 101, 201, 301 Control unit 102, 202 Transmission circuit 103, 203 Reception circuit 104, 204 First local oscillator 105, 205 Second local oscillator 106, 206 First switch 107, 207 Second switch 208 Third switch 209 Fourth switch 110, 210 First mixer 111, 211 Second mixer 112, 212 First unnecessary wave suppression filter 113, 213 Second unnecessary wave suppression filter 114 First transmission antenna 115 Second transmission antenna 214 Third transmission antenna 116 First reception antenna 117 Second reception antenna 216 Third reception antenna 302 Transmission unit 303 Reception unit 304 Transmission unit 305 Reception unit 306 Transmission / reception signal Switching unit 307 Oscillator 308 Amplification times 309 Modulation circuit 310 Demodulation circuit 311 Transmission antenna 312 Reception antenna f1 First communication frequency f2 Second communication frequency f0 Oscillation frequency fd of first local oscillator oscillation frequency fm of second local oscillator After frequency mixing or frequency mixing Previous frequency

Claims (2)

Two transmission antennas for supplying wireless power and transmitting at least a radio signal to IC tags having different communication frequencies, two reception antennas for receiving the radio signal, a transmission circuit, and a reception circuit And a control unit, a first switch, a second switch, a first mixer, a second mixer, a first local oscillator, and a second local oscillator, The transmission circuit and the reception circuit are connected, the first local oscillator is connected to the transmission circuit, the two transmission signal paths are respectively connected to the two transmission antennas, the transmission circuit and the two transmission circuits wherein in placing the first switch and the transmitting circuit capable of switching the connection to the two transmission signal path between the transmit signal path, one of the transmit signal path, the first mixer and the second Bei example only unwanted signal suppression filter, said the first mixer is connected a second local oscillator, and the other transmit signal path, directly connected to the other transmission antenna, transmission from said one transmission antenna The frequency of the transmitted signal matches the frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator, and the frequency of the signal transmitted from the other transmitting antenna is the first frequency The reception circuit and the second switch are connected, and the two reception signal paths are respectively connected to the two reception antennas, and the reception circuit and the two It said second of said receiving circuit by placing the switch and the switchable connections to the two receive signal path between the receive signal path, the one of the receive signal path, the second mixer Preliminary said second only Bei give a spurious wave suppression filter, said the second mixer is connected the second local oscillator, while the other received signal path is connected directly to the other receiving antennas, the one The frequency of the signal received from the receiving antenna matches the frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator, and the frequency of the signal received from the other receiving antenna is An RFID reader / writer characterized by having the same frequency as that of the first local oscillator . A transmission antenna that wirelessly supplies power to an IC tag having a different communication frequency and transmits at least a radio signal, a reception antenna that receives the radio signal, a transmission circuit, a reception circuit, and a control unit A first switch, a second switch, a third switch, a fourth switch, a first mixer, a second mixer, a first local oscillator, and a second local oscillator The control unit is connected to the transmission circuit and the reception circuit, the first local oscillator is connected to the transmission circuit, and the first local oscillator is connected between the transmission circuit and the two transmission signal paths. And by arranging the third switch between the transmission antenna and the two transmission signal paths, a connection to the two transmission signal paths between the transmission circuit and the transmission antenna can be established. It can be switched , One of the transmit signal path, the first mixer and only Bei example the first unnecessary wave suppression filter, said the first mixer the second local oscillator is connected to the other of the transmit signal path The frequency of the signal directly connected to the third switch and transmitted from the one transmitting antenna matches the frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator. The frequency of the signal transmitted from the other transmitting antenna matches the frequency of the first local oscillator, and the second switch is disposed between the receiving circuit and the two received signal paths. Then, by arranging the fourth switch between the reception antenna and the two reception signal paths, the connection to the two reception signal paths between the reception circuit and the reception antenna can be switched , one Received signal path is e Bei only the second mixer and the second unnecessary wave suppression filter, said the second mixer the second local oscillator is connected to the other of the receive signal path, the The frequency of the signal directly connected to the fourth switch and received via the one reception signal path is a frequency obtained by adding the frequency of the first local oscillator and the frequency of the second local oscillator. An RFID reader / writer characterized in that the frequency of a signal that matches and that is received via the other received signal path matches the frequency of the first local oscillator .

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