JP2008258886A - Radio communication equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide radio communication equipment for improving an SN ratio while suitably eliminating a detouring signal from a transmission side included in a received signal by a simple configuration. <P>SOLUTION: Since the radio communication equipment includes a transmission amplifier 24 for outputting a transmission signal; a plurality of antennas 18 for transmitting the transmission signal and also receiving a return signal from a communication object; a plurality of transmission/reception separating parts 26 for separating a transmission signal from the transmission amplifier 24 in accordance with each antenna 18 from a received signal by the antenna 18; a reception signal synthesizing part 28 for synthesizing reception signals respectively received by the plurality of antennas 18; a first phase shifting part 44 provided in a signal transfer route between the transmission amplifier 24 and the transmission/reception separating part 26 in accordance with a prescribed antenna 18; and a second phase shifter 46 provided in a signal transfer route between the transmission/reception separating part 26 and the reception signal synthesizing part 28, the antennas 18 can mutually and effectively suppress a detouring signal from a transmitting side without providing a special configuration. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an improvement of a wireless communication apparatus having a cancel circuit for suppressing a sneak signal from a transmission side.

  2. Description of the Related Art A wireless communication device is known that includes a transmission unit that transmits a predetermined transmission signal from a transmission antenna and a reception unit that receives a reply signal returned in response to the transmission signal by a reception antenna. For example, an RFID (Radio Frequency Identification) system RFID tag communication device (interrogator) that reads information without contact from a small RFID 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.

  By the way, normally, the wireless tag communication device transmits a predetermined transmission signal (question wave) from the antenna toward the wireless tag, and a reply signal (response wave) returned from the wireless tag that has received the transmission signal. Is received by the antenna, and information is communicated with the wireless tag. However, a strong sneak signal (direct wave) from the transmission side is mixed in the received reply signal, increasing the overall received signal strength. There is a case. As a result, the allowable input intensity of the amplifier is exceeded, so that the received signal cannot be sufficiently amplified, and as a result, the return signal component from the wireless tag cannot be sufficiently amplified. There was a problem that the to-noise ratio decreased. Therefore, a technique for removing such a sneak signal from the transmission side has been proposed. For example, this is the information communication apparatus described in Patent Document 1. According to this technique, an attenuator is provided between the circulator and the receiving unit, and the received signal is added to the demodulating unit by attenuating the strength of the addition signal of the received signal and the sneak signal by the attenuator. It is said that the influence of unnecessary signals can be avoided with a simple configuration. For example, in the moving body identification apparatus described in Patent Document 2, a technique has been proposed in which a transmission signal is added to a reception signal via an attenuator and a phase shifter to suppress a sneak signal.

JP 2006-203466 A JP-A-10-62518

  However, in the technique in which the attenuator is provided in the receiving unit as described above, the sneak signal from the transmission side is suppressed and the reply signal from the wireless tag is also suppressed, so the effect of improving the SN ratio cannot be expected. there were. In addition, in the technique of adding a transmission signal to a reception signal via an attenuator and a phase shifter, a new signal path for that purpose must be prepared, and the configuration for suppressing such a sneak signal is complicated. There was a harmful effect of becoming. For this reason, there has been a demand for the development of a wireless communication apparatus that improves the S / N ratio while suitably removing the sneak signal from the transmission side included in the received signal with a simple configuration.

  The present invention has been made in the background of the above circumstances, and the object of the present invention is to improve the S / N ratio while preferably removing the sneak signal from the transmission side included in the reception signal with a simple configuration. It is to provide a wireless communication device.

  In order to achieve such an object, the gist of the present invention is that a transmission signal output unit for outputting a predetermined transmission signal, a transmission signal output from the transmission signal output unit, and the transmission signal are transmitted to the transmission signal. A plurality of antennas for receiving a reply signal returned from the communication target, and a plurality of antennas for separating a transmission signal output from the transmission signal output unit corresponding to each antenna and a reception signal received by the antenna. A transmission / reception separating unit and a reception signal combining unit configured to combine the reception signals respectively received by the plurality of antennas, and communicates information with the communication target using at least one of the plurality of antennas. A wireless communication device, wherein a signal transmission between the transmission signal output unit and the transmission / reception separation unit is performed corresponding to at least one of the plurality of antennas. A first phase shift unit provided in the path, and a second phase shift unit provided in the signal transmission path between the transmission / reception separating unit and the reception signal combining unit are provided. It is.

  In this way, a transmission signal output unit that outputs a predetermined transmission signal, and a transmission signal that is output from the transmission signal output unit and a reply signal that is returned from the communication target according to the transmission signal are received. A plurality of antennas, a plurality of transmission / reception separating sections for separating a transmission signal output from the transmission signal output section corresponding to each antenna and a reception signal received by the antenna, and reception by each of the plurality of antennas A received signal synthesizer for synthesizing the received signals, and a first signal transmission path provided between the transmission signal output unit and the transmission / reception separating unit corresponding to at least one of the plurality of antennas. The first phase shift unit includes a phase shift unit and a second phase shift unit provided in a signal transmission path between the transmission / reception separating unit and the reception signal combining unit. And second by appropriately setting the amount of phase shift of each phase shifter, it is possible to effectively suppress the echo signal from the transmitting side by the plurality of antennas between without providing a special configuration. That is, it is possible to provide a wireless communication apparatus that improves the SN ratio while suitably removing the sneak signal from the transmission side included in the received signal with a simple configuration.

  Here, preferably, the amount of phase shift in each of the first phase shift unit and the second phase shift unit provided corresponding to a predetermined antenna is equal. In this way, in order to effectively suppress the sneak signal from the transmission side between the plurality of antennas while matching the transmission directivity and the reception directivity, the first phase shift unit and the second phase shifter The amount of phase shift of each phase shift part can be set as appropriate.

  Preferably, the transmission signal output unit is provided with n antennas that transmit a transmission signal output from the transmission signal output unit and receive a reply signal returned from a communication target according to the transmission signal. A phase shift amount of the first phase shift unit and the second phase shift unit provided in the kth antenna among the n antennas is a value represented by (k−1) × 360 / 2n. . In this way, a sneak signal from the transmission side can be effectively suppressed between the plurality of antennas.

  Preferably, a delay line is provided as the phase shift section. In this way, a sneak signal from the transmission side can be suppressed between the plurality of antennas with a practical and simple configuration.

  Preferably, a circuit switching unit for individually opening and closing a signal transmission path between each antenna and the transmission / reception separating unit corresponding to the antennas is provided. In the circuit switching unit, connection to the antenna and termination resistance are provided. Either one of the connections can be selected. In this way, in a wireless communication device provided with a so-called diversity antenna, a sneak signal from the transmission side can be effectively suppressed between a plurality of antennas constituting the diversity antenna.

  Preferably, in response to an antenna different from the antenna provided with the first phase shift unit and the second phase shift unit, signal transmission on the antenna side of the transmission / reception separating unit corresponding to the antenna is performed. A path is provided with a third phase shifter. In this way, the sneak signal from the transmission side can be more effectively suppressed between the plurality of antennas.

  Preferably, the transmission signal output unit is provided with two antennas for transmitting a transmission signal output from the transmission signal output unit and receiving a reply signal returned from a communication target according to the transmission signal. The antennas are arranged such that the distance between the two antennas is ¼ of the wavelength of the radio wave used for communication with the communication target. In this way, the transmission directivity of the transmission signal can be directed in the direction in which the two antennas are arranged.

  Preferably, a 90 ° hybrid coupler is provided as the phase shift section. In this way, a sneak signal from the transmission side can be suppressed between the two antennas with a practical and simple configuration.

  Preferably, the wireless communication device transmits a predetermined transmission signal from at least one of the plurality of antennas toward a wireless tag that is a communication target, and the wireless communication device responds to the transmission signal with the wireless communication device. The wireless tag communication device performs communication of information with the wireless tag by receiving a return signal returned from the tag by at least one of the plurality of antennas. In this way, in the RFID tag communication apparatus in which the sneak signal from the transmission side easily affects the S / N ratio, the S / N ratio can be increased while suitably removing the sneak signal from the transmission side included in the reception signal with a simple configuration. Can be improved.

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

FIG. 1 is a diagram for explaining a radio tag communication system 10 to which a radio communication apparatus of the present invention is preferably applied. The wireless tag communication system 10 includes a wireless tag communication device 12 that is an embodiment of the wireless communication device of the present invention and a single or multiple (single in FIG. 1) wireless communication target of the wireless tag communication device 12. The RFID tag is a so-called RFID (Radio Frequency Identification) system. 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 information signal (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 as a response wave F _r (reply signal) to the RFID tag communication apparatus 12, 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 of this embodiment is connected to the wireless tag 14 in order to read / write information with respect to the wireless tag 14 and to detect the direction or position of the wireless tag 14. Communicates information between the two, and executes digital signal processing such as outputting transmission data as a digital signal and reading response data from the wireless tag 14 based on a reply signal from the wireless tag 14 If a DSP (Digital Signal Processor) 16 to the antenna 18a of the plurality (three in FIG. 2) that is shared in the reception of the transmission and the response wave F _r of the interrogating wave F _c, 18b, 18c (hereinafter, not distinguished simply referred to as the antenna 18) to, together with a plurality of antennas 18 performs transmission processing for transmitting the interrogating wave F _c, the plurality of antennas 18 And a reception circuit 20 performs reception processing of the received reception signal, and is configured to include.

The transmission / reception circuit 20 outputs a predetermined frequency signal corresponding to the carrier wave of the interrogation wave F _c and the frequency signal output from the carrier output unit 22 as transmission data supplied from the DSP 16. A transmission amplifier 24 to be modulated and output, and a plurality (three in FIG. 2) for separating a transmission signal output from the transmission amplifier 24 corresponding to each antenna 18 and a reception signal received by each antenna 18 Transmission / reception separators 26a, 26b, and 26c (hereinafter simply referred to as transmission / reception separators 26 unless otherwise specified) and reception received by the plurality of antennas 18 and supplied via the transmission / reception separators 26, respectively. A reception signal combining unit 28 for combining signals, an orthogonal demodulation unit 30 for performing orthogonal demodulation on the combined signal supplied from the reception signal combining unit 28, and An I-phase amplifying unit 32 that amplifies the in-phase component (I-phase signal) output from the AC demodulator 30 and an I-phase that passes only a signal in a predetermined frequency band among the signals output from the I-phase amplifying unit 32 A filter 34, an I-phase A / D converter 36 that converts a signal output from the I-phase filter 34 into a digital signal and supplies the digital signal to the DSP 16, and a quadrature component (Q-phase) output from the quadrature demodulator 30 Q-phase amplification unit 38 that amplifies the signal), a Q-phase filter 40 that passes only a signal in a predetermined frequency band among the signals output from the Q-phase amplification unit 38, and the Q-phase filter 40 that outputs the signal. And a Q-phase A / D converter 42 that converts the signal into a digital signal and supplies the signal to the DSP 16. Here, as the transmission / reception separation unit 26, a well-known circulator, coupler, or the like is preferably used.

  The transmission / reception circuit 20 transmits signals between the transmission amplifier 24 and the transmission / reception separating units 26b and 26c corresponding to at least one of the plurality of antennas 18 (antennas 18b and 18c in FIG. 2). First phase shifters 44b and 44c provided in the path (hereinafter simply referred to as first phase shifter 44 unless otherwise distinguished), transmission / reception separating units 26b and 26c, and received signal combining unit 28; The second phase shifters 46b and 46c (hereinafter simply referred to as the second phase shifter 46 unless otherwise distinguished) provided in the signal transmission path between the two. The configurations and operations of the first phase shifter 44 and the second phase shifter 46 will be described later with reference to FIG.

  The DSP 16 includes a CPU as a central processing unit, a ROM as a read-only memory, and a RAM as a write-and-read memory as needed. The DSP 16 uses a temporary storage function of the RAM and transmits signals according to a program stored in the ROM in advance. The transmission data output unit 50 and the received signal processing unit 52 are control functions for performing communication control of information with the wireless tag 14 and direction detection control of the wireless tag 14. Is functionally equipped.

  The transmission data output unit 50 generates, for example, a predetermined command bit string (transmission bit string) as transmission data to the wireless tag 14, encodes the generated command bit string by the FSK method or the like, and supplies it to the transmission amplifier 24. To do. The transmission data output from the transmission data output unit 50 modulates the carrier wave output from the carrier wave output unit 22 in the transmission amplifier 24, and passes through the first phase shift unit 44, the transmission / reception separation unit 26, and the like. Each antenna 18 transmits a transmission signal toward the wireless tag 14. Thus, in this embodiment, the transmission data output unit 50 and the transmission amplifier 24 function as a transmission signal output unit that outputs a predetermined transmission signal toward the wireless tag 14.

  The received signal processing unit 52 reads out response data from the wireless tag 14 by processing received signals received by the plurality of antennas 18. Specifically, demodulated signals (I-phase signal and Q-phase signal) demodulated by the quadrature demodulator 30 and input via the I-phase A / D converter 36, the Q-phase A / D converter 42, etc. It decodes by FSK system etc., interprets the decoded signal, and reads the information signal (response data) regarding the modulation of the wireless tag 14.

FIG. 3 is a diagram for explaining the configuration of the RFID circuit element 54 provided in the RFID tag 14. As shown in FIG. 3, the RFID tag circuit element 54 includes an antenna unit 56 for transmitting and receiving signals to and from the RFID tag communication device 12, and the RFID tag connected to the antenna unit 56. An IC circuit unit 58 for performing information communication processing with the communication device 12 is provided. The IC circuit unit 58 rectifies the interrogation wave F _c received from the RFID tag communication device 12 received by the antenna unit 56 and the energy of the interrogation wave F _c rectified by the rectification unit 60. Functions as a power supply unit 62 for storing, a clock extraction unit 64 that extracts a clock signal from the carrier wave received by the antenna unit 56 and supplies the clock signal to the control unit 70, and an information storage unit that can store a predetermined information signal The RFID circuit element 58 via the memory unit 66, the modulation / demodulation unit 68 connected to the antenna unit 56 to modulate and demodulate signals, the rectification unit 60, the clock extraction unit 64, the modulation / demodulation unit 68, and the like. And a control unit 70 for controlling the operation of the function. The control unit 70 performs control to store the predetermined information in the memory unit 66 by communicating with the RFID tag communication device 12, and transmits the interrogation wave F _c received by the antenna unit 56 to the modulation / demodulation unit 68. Then, basic control such as control for reflecting and returning the response wave _Fr as the response wave _Fr is executed based on the information signal stored in the memory unit 66.

  FIG. 4 is a diagram for explaining the principle of the first phase shifter 44 and the second phase shifter 46 provided in the transmission / reception circuit 20. In FIG. 4, for simplification of description, in the configuration provided with two antennas 18a and 18b, the first phase shift unit 44 and the second phase shift unit 46 are provided corresponding to one antenna 18b. An example is given. Considering the circuit shown in FIG. 4, there are roughly three types of transmission paths for the sneak signal from the transmission side. First, what can be considered as the first route is a route that passes through the transmission / reception separating unit 26 indicated by a broken line arrow A in FIG. Further, what can be considered as the second route is a route that is input to the receiving side by reflection at the antenna 18 indicated by a broken-line arrow B in FIG. Such reflection at the antennas 18 is caused by impedance mismatch of the antennas 18. Further, a possible third path is a path that is input to the receiving side by jumping between the antennas 18 indicated by a broken line arrow C in FIG. 4, that is, a transmission signal transmitted by a predetermined antenna 18 is transmitted to another antenna 18. Is a route received by Among these three types of paths, the strength of the sneak signal input to the receiving side through the third path C varies depending on the surrounding environment (for example, a reflector disposed around the surroundings). The sneak signal input to the receiving side through the first path A and the second path B does not change as long as the frequency of the carrier wave output from the carrier wave output unit 22 is fixed. Therefore, the first path is adjusted by adjusting the electrical length from the branch point of the transmission signal output from the transmission amplifier 24 to the combining point of the reception signals received by the plurality of antennas 18 for each antenna 18. A wraparound signal passing through A and the second path B can be configured to be attenuated by multiplexing in the reception signal combining unit 28.

  The first phase shifter 44 and the second phase shifter 46 shown in FIG. 4 correspond to the antenna 18a and the transmission / reception separator 26a with respect to the signal transmission path from the transmission amplifier 24 to the received signal combiner 28. It is provided to adjust the electrical length of the provided path and the electrical length of the path provided corresponding to the antenna 18b and the transmission / reception separating unit 26b, and more specifically, a well-known delay. A delay line or a delay circuit in an LC circuit is preferably used. The phase shift amounts of the first phase shifter 44 and the second phase shifter 46 are preferably received from the transmission amplifier 24 provided corresponding to the antenna 18a and the transmission / reception separator 26a. The signal passing through the signal transmission path to the signal synthesis unit 28 and the signal passing through the signal transmission path from the transmission amplifier 24 provided corresponding to the antenna 18b and the transmission / reception separation unit 26b to the reception signal synthesis unit 28 are When the signals are synthesized in the reception signal synthesis unit 28, the signals output from the reception signal synthesis unit 28 are set to values as small as possible by canceling out the signals. That is, preferably, the amount of phase shift in each of the first phase shifter 44 and the second phase shifter 46 provided corresponding to the antenna 18b is equal, and the phase shift amount is 90 °. It is said. Thus, the reason why the phase shift amounts in the first phase shifter 44 and the second phase shifter 46 are equal is to match the transmission directivity and the reception directivity. According to such a configuration, for the signal passing through the signal transmission path from the transmission amplifier 24 to the reception signal synthesis unit 28 provided corresponding to the antenna 18a and the transmission / reception separation unit 26a, the antenna 18b and the transmission / reception separation are performed. The phase of the signal passing through the signal transmission path from the transmission amplifier 24 provided corresponding to the unit 26b to the reception signal synthesis unit 28 is inverted by 180 ° in the reception signal synthesis unit 28, and these signals are received. The signal synthesis unit 28 cancels the synthesis. That is, the sneak signal passing through the first path A and the second path B in FIG. 4 described above is attenuated as much as possible by the multiplexing in the reception signal combining unit 28.

  Returning to FIG. 2, the first phase shifter 44 and the second phase shifter 46 provided in the transmission / reception circuit 20 of the RFID tag communication device 12 basically perform the transmission according to the principle described above. Regarding the signal transmission path from the amplifier 24 to the reception signal combining unit 28, the electrical length of the path provided corresponding to the antenna 18b and the transmission / reception separation unit 26b and the path provided corresponding to the antenna 18c and the transmission / reception separation unit 26c. By adjusting the electrical length, the sneak signal from the transmission side is attenuated as much as possible by the multiplexing in the reception signal synthesis unit 28. That is, the amount of phase shift in each of the first phase shifter 44 and the second phase shifter 46 provided corresponding to each antenna 18 is equal, for example, provided corresponding to the antenna 18b. Further, the amount of phase shift in each of the first phase shifter 44 and the second phase shifter 46 is 60 °, and the first phase shifter 44 and the second phase shifter provided corresponding to the antenna 18c. The amount of phase shift in the phase portion 46 is 120 °. According to such a configuration, for the signal passing through the signal transmission path from the transmission amplifier 24 to the reception signal synthesis unit 28 provided corresponding to the antenna 18a and the transmission / reception separation unit 26a, the antenna 18b and the transmission / reception separation are performed. The phase of the signal passing through the signal transmission path from the transmission amplifier 24 provided corresponding to the unit 26b to the reception signal synthesis unit 28 is different by 120 ° in the reception signal synthesis unit 28 (preferably a delay) ) Further, the phase of the signal passing through the signal transmission path from the transmission amplifier 24 to the reception signal synthesis unit 28 provided corresponding to the antenna 18c and the transmission / reception separation unit 26c differs by 240 ° in the reception signal synthesis unit 28. (Preferably delayed). Then, these signals are canceled by being synthesized in the reception signal synthesis unit 28. That is, the sneak signal input to the reception system through the transmission / reception separation unit 26 and the sneak signal input to the reception system due to reflection due to the impedance mismatch of the antenna 18 are made possible by the combination in the reception signal synthesis unit 28. Is attenuated.

  Here, a configuration in which n antennas 18 are provided in the RFID tag communication apparatus 12 will be considered. The n antennas 18 are ordered by k = 1, 2,..., N, and the first phase shifter 44 and the second phase shifter 46 correspond to the first antenna 18. And the first phase shifter 44 and the second phase shifter 46 having predetermined phase shift amounts corresponding to the other antennas 18, that is, the second to nth antennas 18, respectively. Then, the phase shift amounts of the first phase shifter 44 and the second phase shifter 46 provided in the kth antenna 18 are both expressed by the same (k−1) × 360 / 2n °. By setting the value, a signal passing through a signal transmission path from the transmission amplifier 24 provided corresponding to each antenna 18 and the transmission / reception separation unit 26 to the reception signal synthesis unit 28 is combined by the reception signal synthesis unit 28. It is attenuated as much as possible. That is, by determining the amount of phase shift of each of the phase shift units 44 and 46 in this manner, the reception system is reflected by a sneak signal that passes through the transmission / reception separation unit 26 and is input to the reception system and by reflection due to impedance mismatch of the antenna 18. The sneak signal input to is attenuated as much as possible by the multiplexing in the reception signal synthesis unit 28.

  FIG. 5 shows that in the RFID tag communication device 12 having two antennas 18a and 18b, a 90 ° hybrid coupler is provided as the first phase shift unit 44 and the second phase shift unit 46. It is a figure which illustrates composition. The configurations other than the antenna 18, the transmission amplifier 24, and the transmission / reception separating unit 26 shown in FIG. 5 are the same as those shown in FIG. 2, and are omitted in FIG. In addition, regarding the configuration shown in each part, the same reference numerals are given to the parts common to those shown in FIG. 2 described above, and the description thereof is omitted. In the configuration shown in FIG. 5, the first 90 ° hybrid coupler 72 as the first phase shifter 44 is provided in the signal transmission path between the transmission amplifier 24 and the transmission / reception separator 26. A second 90 ° hybrid coupler 74 that functions as a second phase shifter 46 and a received signal synthesizer is provided on the output side. The first 90 ° hybrid coupler 72 distributes the signal supplied from the transmission amplifier 24 to the transmission / reception separators 26a and 26b, and sets the phase of the signal supplied to the transmission / reception separator 26b to the transmission / reception separator 26a. It has a function of a distributor and a phase shifter that is 90 ° different (preferably delayed) with respect to the signal supplied to. In addition, the second 90 ° hybrid coupler 74 is configured such that the phase of the signal input from the transmission / reception separation unit 26b differs from the signal input from the transmission / reception separation unit 26a by 90 ° (preferably, a delay). And a function of a phase shifter and a multiplexer that multiplexes signals respectively input from the transmission / reception separators 26a and 26b. The signal combined by the second hybrid coupler 74 is input to the quadrature demodulator 30 and is quadrature demodulated as described above. According to such a configuration, for the signal passing through the signal transmission path from the transmission amplifier 24 provided corresponding to the antenna 18a and the transmission / reception separating unit 26a to the second 90 ° hybrid coupler 74, the antenna 18b. And the phase of the signal passing through the signal transmission path from the transmission amplifier 24 provided corresponding to the transmission / reception separating unit 26 b to the second 90 ° hybrid coupler 74 is combined in the second 90 ° hybrid coupler 74. The signals are inverted by 180 °, and these signals are combined by the second 90 ° hybrid coupler 74 and canceled. That is, the sneak signal input to the reception system through the transmission / reception separation unit 26 and the sneak signal input to the reception system due to reflection due to the impedance mismatch of the antenna 18 are combined in the second 90 ° hybrid coupler 74. Is attenuated as much as possible.

  Here, as shown in FIG. 5 described above, two antennas that transmit the transmission signal output from the transmission amplifier 24 and receive the return signal returned from the wireless tag 14 that is a communication target according to the transmission signal. In the configuration including 18a and 18b, the distance between the two antennas 18a and 18b is preferably output from the wavelength of the radio wave used for communication with the wireless tag 14, that is, from the carrier wave output unit 22. It is arranged to be 1/4 of the wavelength of the carrier wave. According to such a configuration, in particular, the antennas 18a and 18b are rod-shaped (linear) antennas such as dipole antennas, and the reception signal combining unit 28 (second 90) is provided between the transmission amplifiers 24 between the antennas 18a and 18b. When the difference in electrical length of the signal transmission path to the hybrid coupler 74) corresponds to a phase of 90 °, the transmission directivity of the transmission signal and the reception of the reception signal in the direction in which the antennas 18a and 18b are arranged. Since the directivity is good, suitable communication with the wireless tag 14 can be realized.

  FIG. 6 shows another configuration in which a 90 ° hybrid coupler is provided as the first phase shift unit 44 and the second phase shift unit 46 in the RFID tag communication apparatus 12 having two antennas 18a and 18b. It is a figure which shows an example. The configurations other than the antenna 18, the transmission amplifier 24, and the transmission / reception separating unit 26 shown in FIG. 6 are the same as those shown in FIG. 2, and are omitted in FIG. Moreover, regarding the structure shown in each part, the same code | symbol is attached | subjected about the part which is common in what was shown in FIG.2 and FIG.5 mentioned above, and the description is abbreviate | omitted. In the configuration shown in FIG. 6, circuit switching for individually opening and closing the signal transmission paths is provided for the signal transmission paths between the antennas 18 a and 18 b and the transmission / reception separation units 26 a and 26 b corresponding to the antennas 18 a and 18 b. Units 76a and 76b (hereinafter, simply referred to as a circuit switching unit 76 unless otherwise distinguished) are provided. The terminal b opposite to the terminal a to which the antenna 18 is connected in each circuit switching unit 76 is grounded via termination resistors 78a and 78b (hereinafter simply referred to as the termination resistor 78 unless otherwise distinguished). Has been. These circuit switching units 76 are connected to the antenna 18 (connection on the terminal a side) and to the termination resistor 78 (connection on the terminal b side) with respect to the transmission / reception separating unit 26 in accordance with a control signal supplied from the DSP 16. ) Is selectively established, and thereby, a radio having a so-called diversity antenna that performs communication with the radio tag 14 using any one of the antennas 18a and 18b. The tag communication device 12 is realized. In such a configuration, only the circuit switching unit 76 corresponding to the antenna 18 used for communication with the wireless tag 14 is connected to the terminal a on the antenna 18 side, and corresponds to the other antenna 18 not used for such communication. By connecting the circuit switching unit 76 to the terminal b on the termination resistor 78 side, the sneak signal from the transmission side caused by the jumping between the antennas is effectively suppressed among the plurality of antennas 18 constituting the diversity antenna. be able to.

  FIG. 7 shows a wireless tag communication device 12 having two antennas 18a and 18b, in which a third phase shifter 80 is provided in addition to the first phase shifter 44 and the second phase shifter 46. FIG. The configuration other than the antenna 18, the transmission amplifier 24, and the transmission / reception separating unit 26 shown in FIG. 7 is the same as that shown in FIG. 2, and is omitted in FIG. In addition, regarding the configuration shown in each part, the same reference numerals are given to the parts common to those shown in FIG. 2 described above, and the description thereof is omitted. In the configuration shown in FIG. 7, the antenna 18a corresponds to an antenna 18a different from the antenna 18b corresponding to the signal transmission path provided with the first phase shifter 44 and the second phase shifter 46. A third phase shifter 80 is provided in the signal transmission path closer to the antenna 18a than the corresponding transceiver 26a. The third phase shifter 80 has an electrical length of a path provided corresponding to the antenna 18a and the transmission / reception separator 26a, an antenna 18b, and a transmission / reception with respect to the signal transmission path from the transmission / reception separator 26 to the antenna 18. It is provided to adjust the electrical length of the path provided corresponding to the separation unit 26b, and is well known in the same manner as the first phase shift unit 44 and the second phase shift unit 46. A delay line or a delay circuit in an LC circuit is preferably used. The amount of phase shift of the third phase shift unit 80 is preferably equal to that of the first phase shift unit 44 and the second phase shift unit 46. According to such a configuration, regarding the signal transmission path from the transmission amplifier 24 to the antenna 18 and the signal transmission path from the antenna 18 to the reception signal combining unit 28, the electrical length of the path corresponding to the antenna 18a and the antenna 18b are supported. The transmission lengths and reception directivities of the antennas 18a and 18b can be made equal to each other, especially when the VSWR (Voltage Standing Wave Ratio) of the antenna 18 is relatively low. Can be directed to the front.

  Thus, according to the present embodiment, the transmission amplifier 24 and the transmission data output unit 50 functioning as a transmission signal output unit that outputs a predetermined transmission signal, and the transmission signal output from the transmission amplifier 24 are transmitted. A plurality of antennas 18 that receive a reply signal returned from the wireless tag 14 that is a communication target according to the transmission signal, a transmission signal output from the transmission amplifier 24 corresponding to each antenna 18, and the antenna 18 A plurality of transmission / reception separators 26 that separate received received signals, a received signal combiner 28 that combines received signals respectively received by the plurality of antennas 18, and at least one antenna among the plurality of antennas 18. Corresponding to the first phase shifter 44 provided in the signal transmission path between the transmission amplifier 24 and the transmission / reception separator 26, Since the second phase shift unit 46 provided in the signal transmission path between the transmission / reception separating unit 26 and the received signal combining unit 28 is provided, the first phase shift unit 44 and the first phase shift unit 44 are provided. By appropriately setting the phase shift amount of each of the two phase shift units 46, a sneak signal from the transmission side can be effectively suppressed between the plurality of antennas 18 without providing a special configuration. That is, it is possible to provide a wireless communication apparatus that improves the SN ratio while suitably removing the sneak signal from the transmission side included in the received signal with a simple configuration.

  Further, since the amount of phase shift in each of the first phase shifter 44 and the second phase shifter 46 provided corresponding to the predetermined antenna 18 is equal, the transmission directivity and the reception directivity are matched. In order to effectively suppress the sneak signal from the transmission side between the plurality of antennas 18, the respective phase shift amounts of the first phase shift unit 44 and the second phase shift unit 46 are appropriately set. be able to.

  In addition, it includes n antennas 18 that transmit a transmission signal output from the transmission amplifier 24 and receive a return signal returned from the wireless tag 14 that is a communication target according to the transmission signal. Of the n antennas 18, the amount of phase shift of the first phase shifter 44 and the second phase shifter 46 provided in the kth antenna 18 is represented by (k−1) × 360 / 2n. Therefore, a sneak signal from the transmission side can be effectively suppressed between the plurality of antennas 18.

  In addition, since the phase shift units 44, 46, and 80 are provided with delay lines, a sneak signal from the transmission side between the plurality of antennas 18 can be suppressed with a practical and simple configuration.

  In addition, a circuit switching unit 76 for individually opening and closing a signal transmission path between each antenna 18 and the transmission / reception separating unit 26 corresponding to the antenna 18 is provided, and the circuit switching unit 76 connects and terminates the antenna 18. Since either one of the connections to the resistor 78 can be selected, in a wireless communication apparatus having a so-called diversity antenna, a sneak signal from the transmission side is transmitted between the plurality of antennas 18 constituting the diversity antenna. It can be effectively suppressed.

  Also, corresponding to the antenna 18 different from the antenna 18 provided with the first phase shift unit 44 and the second phase shift unit 46, the antenna 18 side of the transmission / reception separating unit 26 corresponding to the antenna 18 is provided. Since the third phase shifter 80 is provided in the signal transmission path, a sneak signal from the transmission side can be more effectively suppressed between the plurality of antennas 18.

  In addition, the transmission amplifier 24 includes two antennas 18 that transmit a transmission signal output from the transmission amplifier 24 and receive a reply signal returned from the wireless tag 14 that is a communication target according to the transmission signal. Since the distance between the two antennas 18 is arranged to be ¼ of the wavelength of the radio wave used for communication with the wireless tag 14, the transmission directivity of the transmission signal is 2 The two antennas 18 can be directed in a line.

  In addition, since the 90 ° hybrid couplers 72 and 74 are provided as the phase shift unit, a sneak signal from the transmission side between the two antennas 18 can be suppressed with a practical and simple configuration.

  The wireless communication apparatus according to the present embodiment transmits a predetermined transmission signal by at least one antenna 18 among the plurality of antennas 18 toward the wireless tag 14 that is a communication target, and responds to the transmission signal. Since the wireless tag communication device 12 communicates information with the wireless tag 14 by receiving a reply signal returned from the wireless tag 14 by at least one antenna 18 among the plurality of antennas 18. In the RFID tag communication apparatus 12 in which the sneak signal from the transmission side easily affects the S / N ratio, the S / N ratio can be improved while suitably removing the sneak signal from the transmission side included in the reception signal with a simple configuration. .

  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 RFID tag communication apparatus 12 can connect the plurality of antennas 18 to each other without providing a special configuration via the first phase shift unit 44, the second phase shift unit 46, and the like. However, the present invention is not limited to this. For example, in addition to the configuration shown in FIG. 2 described above, output (distribution) from the carrier output unit 22 is performed. It may be configured to generate a cancel signal by controlling the phase and / or amplitude of the carrier wave to be added, and add the cancel signal to the combined signal output from the received signal combining unit 28. According to such a configuration, there is an advantage that a sneak signal from the transmission side caused by jumping between the antennas 18 can be suppressed particularly efficiently.

  In the above-described embodiment, the reception signal combining unit 28 combines the reception signals as analog signals input from the antennas 18 via the transmission / reception separation unit 26 and the like. The digital signal may be converted into a digital signal and temporarily stored in the memory unit, and then the received signal stored in the memory unit may be read and combined. In this case, the received signal as a digital signal is combined. It is supposed to be. As described above, the configuration of each unit provided in the RFID tag communication apparatus 12 may process a digital signal.

  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 the radio | wireless communication apparatus of this invention is applied suitably. It is a figure explaining the structure of the radio | wireless tag communication apparatus which is one Example of the radio | wireless communication apparatus 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 principle of the 1st phase shift part with which the transmission / reception circuit of the RFID tag communication apparatus of FIG. 2 was equipped, and the 2nd phase shift part. The figure which illustrates the structure provided with the 90 degree hybrid coupler as a 1st phase shift part and a 2nd phase shift part in the structure provided with two antennas which is a modification of the RFID tag communication apparatus of FIG. It is. 2 is a modification of the RFID tag communication apparatus of FIG. 2, and illustrates another configuration in which a 90 ° hybrid coupler is provided as the first phase shift unit and the second phase shift unit in the configuration including two antennas. It is a figure to do. A configuration provided with two antennas, which is a modification of the RFID tag communication apparatus of FIG. 2, is provided with a third phase shifter in addition to the first phase shifter and the second phase shifter. FIG.

Explanation of symbols

12: RFID tag communication device (wireless communication device)
14: Radio tag 18: Antenna 24: Transmission amplifier 26: Transmission / reception separation unit 28: Received signal synthesis unit 44: First phase shift unit 46: Second phase shift unit 50: Transmission data output unit 72: First 90 ° Hybrid coupler (first phase shifter)
74: Second 90 ° hybrid coupler (second phase shifter, received signal synthesizer)
76: Circuit switching unit 78: Termination resistor 80: Third phase shift unit

Claims (9)

A transmission signal output unit for outputting a predetermined transmission signal, a plurality of antennas for transmitting a transmission signal output from the transmission signal output unit and receiving a return signal returned from a communication target according to the transmission signal; A plurality of transmission / reception separators for separating a transmission signal output from the transmission signal output unit corresponding to each antenna and a reception signal received by the antenna, and a reception signal received by each of the plurality of antennas A wireless communication device that performs communication of information with the communication target through at least one of the plurality of antennas,
A first phase shifter provided in a signal transmission path between the transmission signal output unit and the transmission / reception separation unit corresponding to at least one of the plurality of antennas;
A wireless communication apparatus comprising: a second phase shift unit provided in a signal transmission path between the transmission / reception separating unit and the received signal combining unit.   2. The wireless communication apparatus according to claim 1, wherein the amount of phase shift in each of the first phase shift section and the second phase shift section provided corresponding to a predetermined antenna is the same.   The antenna includes n antennas that transmit a transmission signal output from the transmission signal output unit and receive a reply signal returned from a communication target according to the transmission signal, and out of the n antennas 3. The wireless communication according to claim 2, wherein a phase shift amount of the first phase shift unit and the second phase shift unit provided in the k th antenna is a value represented by (k−1) × 360 / 2n. apparatus.   4. The wireless communication apparatus according to claim 1, wherein a delay line is provided as the phase shift unit.   A circuit switching unit that individually opens and closes a signal transmission path between each antenna and a transmission / reception separating unit corresponding to the antenna, and in the circuit switching unit, either one of connection to the antenna and connection to a termination resistor The wireless communication apparatus according to claim 1, wherein connection is selectable.   Corresponding to an antenna different from the antenna provided with the first phase shift unit and the second phase shift unit, a third phase shift is performed in the signal transmission path on the antenna side of the transmission / reception separating unit corresponding to the antenna. The wireless communication apparatus according to claim 1, further comprising a phase section.   The apparatus includes two antennas that transmit a transmission signal output from the transmission signal output unit and receive a reply signal returned from a communication target according to the transmission signal, and a distance between the two antennas The wireless communication device according to claim 1, wherein the wireless communication device is arranged to be ¼ of a wavelength of a radio wave used for communication with the communication target.   The wireless communication apparatus according to claim 7, comprising a 90 ° hybrid coupler as the phase shift unit.   The wireless communication device transmits a predetermined transmission signal to at least one of the plurality of antennas toward a wireless tag that is a communication target, and returns a reply from the wireless tag in response to the transmission signal. 9. The wireless communication device according to claim 1, wherein the wireless communication device is a wireless tag communication device that communicates information with the wireless tag by receiving a signal through at least one of the plurality of antennas.

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