JP4360354B2 - Wireless tag communication device - Google Patents

Description

  The present invention relates to a wireless tag communication device that performs communication with a wireless tag capable of wirelessly writing and reading information, and more particularly to improvement of communication directivity control.

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

  In communication devices such as the above-described RFID tag communication device, communication directivity is often controlled in order to increase communication sensitivity, and various techniques for suitably controlling such communication directivity have been proposed. Yes. For example, this is the directivity control of a radar apparatus described in Patent Document 1. According to this technique, in an array antenna that includes a plurality of antenna elements and performs phased array control, among the plurality of antenna elements, the antenna elements used for communication can be selectively switched to change the mutual spacing of the antenna elements. The directivity characteristics can be controlled, and the reception sensitivity can be adapted to the entire region to be searched without reducing the maximum distance and the maximum sensitivity.

JP-A-6-174823

  However, with the conventional technology, it has been difficult to suitably determine communication directivity with the wireless tag. That is, the interval between a plurality of antenna elements constituting an array antenna in RFID is generally about 1/2 to 1 times the wavelength of a carrier wave, and the main lobe (radiation pattern that maximizes communication sensitivity) becomes sharper as the interval increases. However, by doing so, there is a possibility that a grating lobe (unnecessary radiation pattern) may be generated, and there is an adverse effect that the antenna needs to be enlarged. Further, when the mutual interval between the antenna elements is changed, a coefficient (weight) to be multiplied corresponding to each element has to be changed. However, there is no technique that can suitably set the weight. In general, in RFID, it is desired to appropriately set communication directivity with the wireless tag in accordance with the purpose of communication. Therefore, development of a wireless tag communication device that realizes such control has been demanded.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a wireless tag communication device capable of appropriately setting the communication directivity with the wireless tag according to the communication purpose. There is.

  In order to achieve such an object, the gist of the present invention is to transmit a transmission signal to the wireless tag and receive a reply signal returned from the wireless tag in response to the transmission signal. A wireless tag communication device for communicating information with the wireless tag, having a plurality of antenna elements, and changing an interval between at least two antenna elements used for communication with the wireless tag Communication between the wireless tag by setting a weight for changing at least the phase of each of the signals corresponding to the antenna elements in accordance with the distance between the antenna elements in the array antenna and the antenna elements in the array antenna A directivity control unit that controls directivity is provided.

  According to this configuration, the array antenna having a plurality of antenna elements and capable of changing the interval between at least two antenna elements used for communication with the wireless tag, and the antenna elements in the array antenna are mutually connected. A directivity control unit that controls communication directivity with the wireless tag by setting a weight for changing at least the phase of each of the signals corresponding to the antenna elements according to the interval between them, Therefore, in addition to being able to arbitrarily control the directivity characteristics by changing the distance between the antenna elements involved in communication with the wireless tag, by setting a predetermined weight according to the distance Communication directivity can be suitably determined. That is, it is possible to provide a wireless tag communication device that can appropriately set the communication directivity with the wireless tag according to the purpose of communication.

  Here, preferably, a storage unit that stores a plurality of sets of weight tables predetermined for each interval between the antenna elements is provided, and the directivity control unit includes a plurality of sets of weights stored in the storage unit. One set of weight tables is read and set in accordance with the distance between the antenna elements. In this way, it is possible to set a weight suitable for the interval between antenna elements involved in communication with the wireless tag in a practical manner.

  Preferably, the directivity control unit controls the communication directivity so that the main lobe in communication with the wireless tag has a desired beam width. . In this way, the beam width of the main lobe in communication with the wireless tag can be suitably controlled.

  Preferably, the array antenna can mechanically change an interval between at least two antenna elements used for communication with the wireless tag. In this way, the interval between the antenna elements involved in communication with the wireless tag can be changed in a practical manner, for example, with a manual knob or the like.

  Preferably, the apparatus further includes a power generator and a power transmission device for mechanically changing a distance between at least two antenna elements used for communication with the wireless tag. If it does in this way, the space | interval between the antenna elements involved in the communication between the said radio | wireless tags can be changed in a practical aspect using an electric motor etc., for example.

  Preferably, the apparatus further includes a detection device that detects an interval between at least two antenna elements used for communication with the wireless tag. If it does in this way, according to the space | interval detected by the detection apparatus, the communication directivity between the said radio | wireless tags can be controlled by the said directivity control part in a practical aspect.

  Preferably, the array antenna has three or more antenna elements, and antenna selection for selecting at least two antenna elements used for communication with the wireless tag among the antenna elements. It has a part. In this way, the interval between antenna elements involved in communication with the wireless tag can be changed in a practical manner.

  Preferably, the array antenna can change an interval between at least two antenna elements used for transmitting a transmission signal to the wireless tag, and the directivity control unit includes the array antenna. A predetermined transmission weight is set according to an interval between the antenna elements in the antenna. In this way, transmission directivity in communication with the wireless tag can be suitably controlled.

  Preferably, the array antenna is capable of changing an interval between at least two antenna elements used for receiving a reception signal returned from the wireless tag, and the directivity control unit includes: A predetermined reception weight is set in accordance with an interval between the antenna elements in the array antenna. In this way, reception directivity in communication with the wireless tag can be suitably controlled.

  Preferably, when an interval between the antenna elements is less than a predetermined value, communication with the wireless tag is performed while changing directivity by the directivity control unit, and the antenna elements are mutually connected. When the interval between them is equal to or greater than a predetermined value, the directivity set by the directivity control unit is fixed and communication with the wireless tag is performed. In this way, communication with the wireless tag can be performed in a suitable manner in accordance with directivity characteristics corresponding to the distance between the antenna elements.

  Preferably, the plurality of antenna elements transmit and receive a transmission signal toward the wireless tag, and are used for both transmission and reception used for receiving a reply signal returned from the wireless tag according to the transmission signal. Antenna element. In this way, the configuration of the array antenna can be simplified as much as possible, and the transmission directivity and the reception directivity in communication with the wireless tag can be suitably controlled.

  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 wireless tag communication system 10 in which the wireless tag communication device of the present invention is preferably used. The RFID tag communication system 10 includes an RFID tag communication device 12 according to an embodiment of the present invention, and a single or plural (single in FIG. 1) RFID tags 14 that are communication targets of the RFID tag communication device 12. It is a so-called RFID (Radio Frequency Identification) system, and the RFID tag communication device 12 functions as an interrogator of the RFID system, and the RFID tag 14 functions as a responder. That is, when the interrogation wave F _c (transmission signal) is transmitted from the radio tag communication apparatus 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 to the RFID tag communication apparatus 12 as a response wave F _r (reply signal), so that information is transmitted between the RFID tag communication apparatus 12 and the RFID tag 14. Communication takes place. The wireless tag communication system 10 is used, for example, for managing articles in a predetermined communication area. The wireless tag 14 is preferably attached to an article to be managed, for example. And are provided integrally. The wireless tag communication device 12 is preferably a portable device provided so as to be relatively movable with respect to an article or the like to be managed, and the user can detect the wireless tag 14 by detecting the wireless tag communication. The device 12 is carried and the wireless tag 14 is detected while referring to a screen displayed on the display unit 22 of the wireless tag communication device 12.

  FIG. 2 is a plan view for explaining the external appearance of the RFID tag communication device 12, and FIG. 3 is a rear view of FIG. 2 viewed from the direction of arrow III. As shown in FIGS. 2 and 3, the wireless tag communication device 12 includes a flat plate-like main body unit 16 having a predetermined thickness and an antenna unit 18 provided on a side portion of the main body unit 16. . The main unit 16 includes a flat housing 20 having a predetermined thickness, a display unit 22 provided on a flat surface of the housing 20, and a side of the display unit 22 on the flat surface of the housing 20. The operation unit 24 provided and an audio output unit 26 having a speaker on the side of the display unit 22 in the plane part of the housing 20 are provided.

  The display unit 22 is a video display device for displaying video (image) indicating various information related to communication with the wireless tag 14, and a liquid crystal display panel or the like is preferably used. The operation unit 24 includes input devices such as predetermined keys, buttons, switches, or pads, and various operations related to the display of the display unit 22 and the detection of the wireless tag 14 can be performed using these input devices. It can be done. The audio output unit 26 is an audio generator for outputting various dial sounds related to communication with the wireless tag 14, and a buzzer, an alarm, a chime speaker, or the like is preferably used.

  The antenna unit 18 is provided with a unit base 28 that is provided integrally with the housing 20 and a pair of left and right that is provided so as to protrude from the unit base 28 to the left and right and that can change the extension dimension from the unit base 28. Support arms 30a and 30b (hereinafter simply referred to as support arms 30 unless otherwise specified), an adjustment knob 32 for changing the extension dimension of the support arms 30 from the unit base 28, and the unit base 28 A plurality of (three in FIGS. 2 and 3) antenna elements 34a, 34b, and 34c that are erected so as to be parallel to each other at the center portion of each of the pair of support arms 30 and the end portions on the opposite side to the unit base portion 28. (Hereinafter, simply referred to as the antenna element 34 unless otherwise distinguished). The plurality of antenna elements 34 transmit and receive a transmission signal toward the wireless tag 14 and also use a transmission / reception shared antenna element used to receive a reply signal returned from the wireless tag 14 in response to the transmission signal. An array antenna 36 is constituted by the three antenna elements 34a, 34b, and 34c. Further, as will be described later with reference to FIGS. 8 to 10, in the operation of changing the extension dimension of the support arm 30 by the adjustment knob 32, the distance between the antenna elements 34b and 34c with respect to the central antenna element 34a is always equal. In other words, the distance between the antenna elements 34a and 34b is always equal to the distance between the antenna elements 34a and 34c. Preferably, the unit base 28 includes a predetermined locking tool (not shown), and the locking tool is engaged with a locking part (not shown) provided at a predetermined portion of the main unit 16. Thus, it can be attached to and detached from the main unit 16.

  FIG. 4 is a diagram illustrating the configuration of the wireless tag communication device 12. As shown in FIG. 4, the wireless tag communication device 12 includes a command bit string generation unit 38 that generates a command bit string corresponding to a transmission signal to the wireless tag 14, and a digital signal output from the command bit string generation unit 38. An FSK encoder 40 that encodes a signal using the FSK method; an AM modulator 42 that modulates the signal encoded by the FSK encoder 40 using the AM method and supplies (stores) the signal to the transmission memory unit 44; A transmission weight multiplication unit 46 that is a transmission PAA (Phased Array Antenna) processing unit that reads a transmission signal stored in the transmission memory unit 44 at any time and multiplies a predetermined transmission weight (transmission PAA weight), and a transmission weight multiplication unit thereof The transmission weight multiplied by 46 and the reception weight multiplied by the reception weight multiplication unit 56 described later are controlled (calculated). ) And a PAA weight controller 48 which includes. In addition, a weight memory unit 49 that is a storage unit (register) that stores a plurality of predetermined weights is provided, and the PAA weight control unit 48 is preferably stored in the weight memory unit 49. It functions as a directivity control unit that controls communication directivity with the wireless tag 14 by reading and setting any one of a plurality of sets of weights.

  In addition, the local oscillator 50 that outputs a predetermined local oscillation signal, and the transmission signal output from the transmission weight multiplication unit 46 according to the local oscillation signal output from the local oscillator 50 are up-converted and output, A plurality (three in FIG. 4) of down-converting the received signals respectively received by the plurality of antenna elements 34 in accordance with the local signals output from the local oscillator 50 and supplying (storing) the received signals to the reception memory unit 54 High frequency transmission / reception units 52a, 52b, and 52c (hereinafter simply referred to as a high frequency transmission / reception unit 52 unless otherwise distinguished).

  The reception weight multiplication unit 56 is a reception PAA processing unit that reads the reception signal stored in the reception memory unit 54 as needed and multiplies a predetermined reception weight (reception PAA weight) supplied from the PAA weight control unit 48. An AM demodulating unit 58 that detects an AM demodulated wave by demodulating the received signal output from the reception weight multiplying unit 56 by the AM method, and an AM demodulated wave demodulated by the AM demodulating unit 58 is decoded by the FSK method. And a response bit string interpretation unit 62 that interprets a decoded signal decoded by the FSK decoding unit 60 and reads an information signal related to the modulation of the wireless tag 14. Further, as will be described later with reference to FIG. 10, the antenna unit 18 is provided with an element position sensor 64 for detecting the position of at least one of the plurality of antenna elements 34. The wireless tag communication device 12 functionally includes an element interval detection unit 66 that detects an interval between the plurality of antenna elements 34 in accordance with a detection result by the element position sensor 64.

  FIG. 5 is a diagram for explaining in detail the configuration of the transmission weight multiplying unit 46. As shown in FIG. 5, the transmission weight multiplication unit 46 multiplies the transmission signal read from the transmission memory unit 44 by the transmission PAA weight supplied from the PAA weight control unit 48. A plurality (three in FIG. 5) of multipliers 68a, 68b, 68c (hereinafter simply referred to as multiplier 68 unless otherwise specified) are provided. Here, the multiplier 68a corresponds to the high frequency transmission / reception unit 52a, the multiplier 68b corresponds to the high frequency transmission / reception unit 52b, and the multiplier 68c corresponds to the high frequency transmission / reception unit 52c, and the output from each multiplier 68 corresponds. The high frequency transmission / reception unit 52 is supplied.

  FIG. 6 is a diagram for explaining the configuration of the high-frequency transmitter / receiver 52 in detail. As shown in FIG. 6, the high frequency transmitter / receiver 52 includes a transmission signal D / A converter 70 for converting the transmission signal supplied from the transmission weight multiplier 46 into an analog signal, and the transmission signal D / A conversion. A transmission signal bandpass filter 71 for extracting only a necessary frequency band from the transmission signal analog-converted by the transmitter 70, and a local oscillation signal output from the local oscillator 50 for the frequency of the signal extracted by the transmission signal bandpass filter 71. An up-converter 72 that increases the frequency of the signal, a transmission signal amplifier 74 that amplifies the transmission signal up-converted by the up-converter 72, and a transmission signal output from the transmission signal amplifier 74 via a high-frequency bandpass filter 77. Supplied to the corresponding antenna element 34 and supplied from the antenna element 34. A directional coupler 76 that supplies the received signal to the received signal amplifier 78 via the high-frequency signal bandpass filter 77, a received signal amplifier 78 that amplifies the received signal supplied from the directional coupler 76, and A down converter 80 that lowers the frequency of the reception signal output from the reception signal amplifier 78 by the frequency of the local oscillation signal output from the local oscillator 50, and a necessary frequency of the reception signals down-converted by the down converter 80 A reception signal band pass filter 81 for extracting only a band; and a reception signal A / D converter 82 for converting the signal extracted by the reception signal band pass filter 81 into a digital signal and supplying the digital signal to the reception memory unit 54. Yes.

  FIG. 7 is a diagram for explaining the configuration of the reception weight multiplication unit 56 in detail. As shown in FIG. 7, the reception weight multiplication unit 56 multiplies each reception signal read from the reception memory unit 54 by a predetermined reception PAA weight supplied from the PAA weight control unit 48 (FIG. 7). 3) multipliers 84a, 84b, 84c (hereinafter simply referred to as multipliers 84 unless otherwise specified) and signals output from these multipliers 84 are synthesized and supplied to the AM demodulator 58. And a synthesizer 86. Here, the multiplier 84a corresponds to the high frequency transmitter / receiver 52a, the multiplier 84b corresponds to the high frequency transmitter / receiver 52b, and the multiplier 84c corresponds to the high frequency transmitter / receiver 52c.

FIG. 8 is a diagram for explaining the configuration of the RFID circuit element 88 provided in the RFID tag 14. As shown in FIG. 8, the RFID circuit element 88 processes an antenna unit 90 for transmitting and receiving signals to and from the RFID tag communication apparatus 12 and a signal received by the antenna unit 90. And an IC circuit unit 92 for the purpose. The IC circuit unit 92 rectifies the interrogation wave F _c received from the RFID tag communication apparatus 12 received by the antenna unit 90 and the energy of the interrogation wave F _c rectified by the rectification unit 94. Functions as a power supply unit 96 for storing, a clock extraction unit 98 that extracts a clock signal from the carrier wave received by the antenna unit 90 and supplies the clock signal to the control unit 104, and an information storage unit that can store a predetermined information signal The RFID circuit element 88 via the memory unit 100, the modem unit 102 connected to the antenna unit 90 for modulating and demodulating the signal, the rectifier unit 94, the clock extracting unit 98, the modem unit 102, and the like. And functionally includes a control unit 104 for controlling the operation. The control unit 104 performs control for storing the predetermined information in the memory unit 100 by communicating with the RFID tag communication device 12, and transmits the interrogation wave F _c received by the antenna unit 90 to the modulation / demodulation unit 102. 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 100.

FIG. 9 and FIG. 10 are diagrams for explaining a change in the interval between the antenna elements 34 in the antenna unit 18 of the RFID tag communication apparatus 12. As described above, the antenna unit 18 is configured so that the extension dimension of the pair of support arms 30a and 30b from the unit base portion 28 can be changed by turning the adjustment knob 32. The plurality of antenna elements 34 a, 34 b, 34 c are erected so as to be parallel to each other at the center of the unit base 28 and the ends of the pair of support arms 30 opposite to the unit base 28. Thus, the distance between the plurality of antenna elements 34 is mechanically changed by changing the extension dimension of the pair of support arms 30a, 30b from the unit base 28 by the above operation. cage, the gear unit 106 as shown in FIG. 11 to be described later, a state where the element spacing as shown in FIG. 9 are 1 times the wavelength of the interrogating wave F _c, between the states of the state and 10 in FIG. 9 of the state state element spacing is 3/4 times the wavelength of the interrogating wave F _c, where and element spacing as shown in FIG. 10 is a half the wavelength of the interrogating wave F _c is Either It is configured to be switched.

  FIG. 11 is a partial cross-sectional view for explaining in detail the internal structure of the portion surrounded by the alternate long and short dash line in the antenna unit 18 shown in FIG. 9, and shows a detail from the unit base portion 28 of the pair of support arms 30 a and 30 b. The gear device 106 for changing the extension dimension (projection amount) is shown. The unit base 28 accommodates the gear device 106 in an internal space thereof, and accommodates the pair of support arms 30a and 30b so that the extension dimension from the unit base 28 can be changed. That is, the pair of support arms 30a and 30b are fitted to the unit base portion 28 so as to be slidable in the respective axial directions. As shown in FIG. 11, gear grooves 108 for meshing gears are continuous in the longitudinal direction of each of the support arms 30 a and 30 b on the side portions (side portions facing each other) of the pair of support arms 30 a and 30 b. And it is dug in a straight line. A central gear 110 is provided integrally with the adjustment knob 32 so as not to rotate relative to the adjustment knob 32 and to rotate about the axis of the unit base 28. The first gear 112 and the second gear 114 are provided between the gear groove 108 provided in the support arm 30 and the central gear 110 so as to be able to rotate about the axis with respect to the unit base 28, so that The gear groove 108 and the central gear 110 are meshed with each other through the first gear 112 and the second gear 114.

  In the gear device 106 configured as described above, when the adjustment knob 32 is rotated in the direction indicated by the arrow, the central gear 110 provided so as not to rotate relative to the adjustment knob 32 is rotated in the same direction. Along with this, the first gear 112 and the second gear 114 are rotated about the axis, whereby the support arms 30a and 30b are driven in the directions indicated by the arrows. When the adjustment knob 32 is rotated in the direction opposite to the direction indicated by the arrow, the support arms 30a and 30b are driven in the direction opposite to the direction indicated by the arrow. With such a mechanism, as the adjustment knob 32 rotates, the pair of support arms 30 protrudes (or is pulled in) from the unit base 28 by the same length, and the antenna element 34b with respect to the central antenna element 34a. And the distance of 34c is changed.

In addition, as shown in FIG. 11, the unit base portion 28 is provided with a recess 116 for element spacing corresponding to at least one of the pair of support arms 30 in a portion facing the support arm 30. When the extension dimension of the support arm 30 from the unit base 28 reaches a predetermined length, the protrusion 118 such as a leaf spring provided on the support arm 30 protrudes and fits into the recess 116. The position of the support arm 30 is determined. The recess 116 is preferably 1 times the wavelength intervals the interrogating wave _{F c} between the antenna elements 34 mutually, 3/4-fold, 1/2-fold to become the pair of support arms 30a, 30b above the They are provided at positions corresponding to the extension dimensions from the unit base portion 28, respectively, so that the interval between the antenna elements 34 can be suitably determined when the adjustment knob 32 is manually operated. Preferably, the concave portion 116 is provided with a sensor device such as a switch. When the protruding portion 118 of the support arm 30 is fitted, the extension size and extension of the support arm 30 from the unit base portion 28 are increased. It functions as an element position sensor 64 for detecting the position of the antenna element 34b or 34c. The element position sensor 64 may be provided on the support arm 30 (projecting portion 118) side. Note that the element position sensor 64 allows the antenna element 34a and 34b to always have the same distance between the antenna elements 34a and 34b and the distance between the antenna elements 34a and 34c. By detecting the position of at least one of 34b and 34c, the distance between the antenna elements 34b and 34c with respect to the central antenna element 34a can be detected. The interval between them can be detected.

12 and 13 are diagrams for explaining the difference in directivity pattern depending on the distance between the antenna elements 34. FIG. 12 shows the directivity pattern in the main lobe direction θ = 0 °, and FIG. 13 shows the main lobe direction. A directivity pattern of θ = 30 ° is shown respectively. Further, in these figures, a directional pattern in which the element interval is set to 1 times the wavelength of the interrogating wave F _c by the solid line, the element spacing is 3/4 times the wavelength of the interrogating wave F _c The directivity pattern in the state is indicated by a broken line, and the directivity pattern in a state where the element interval is ½ times the wavelength of the interrogation wave F _c is indicated by a one-dot chain line. As shown in these figures, when the distance between the plurality of antenna elements 34 mutually and relatively wide and 1 times the wavelength of the interrogating wave F _c is an array antenna composed of a plurality of antenna elements 34 directivity of 36 relatively sharp is a (narrow beam) that, when the spacing between the plurality of antenna elements 34 mutually was 3/4 and the middle of the wavelength of the interrogating wave F _c is the plurality The array antenna 36 constituted by the antenna elements 34 has a middle directivity (middle beam), and the interval between the plurality of antenna elements 34 is relatively ½ times the wavelength of the interrogation wave F _c. When narrowed, the directivity of the array antenna 36 constituted by the plurality of antenna elements 34 is relatively wide (wide beam). Thus, the main lobe (radiation pattern that maximizes the communication sensitivity) becomes sharper as the element spacing increases, and conversely, the main lobe increases as the element spacing decreases. For example, in the search control of the wireless tag 14, when the position where the wireless tag 14 that is the search target is not known at all, communication is performed with a directivity pattern having a relatively large main lobe. As a search area, the approximate position of the wireless tag 14 can be quickly detected. Further, when the position where the wireless tag 14 is present is roughly known, the detailed position where the wireless tag 14 is present is detected by performing communication with a directivity pattern having a relatively sharp main lobe. be able to. As described above, in the communication with the wireless tag 14 by the wireless tag communication device 12, it is desirable that the communication directivity with the wireless tag 14 can be arbitrarily changed, and the wireless tag communication device 12 of the present embodiment. Then, as described above, since the interval between the antenna elements 34 can be changed, the optimum communication directivity can be selected according to the purpose.

FIG. 14 is a diagram for explaining a plurality of sets of weights stored in the weight memory unit 49. As shown in FIG. 14, the weight memory unit 49 stores in advance a plurality of sets of transmission / reception PAA weights W ₀ , W ₁ , W ₂ in accordance with the distance between the antenna elements 34 in the array antenna 36. ing. The value of the weight (complex weight), for example _{if W 1} corresponds to the center of the antenna element _{is ^{W 0 = e jφ, W 1}} = e j0 = 1, W 2 = e -jφ. Here, φ = (2π / λ) × d × sin θ (where λ is the wavelength of the carrier wave, d is the element spacing, and θ is the direction of the main lobe). For example, a transmission / reception PAA weight corresponding to a case where the interval between the plurality of antenna elements 34 is ½ times the wavelength of the interrogation wave F _c is stored in the weight table A, and the interval between the plurality of antenna elements 34 is Is set to 3/4 times the wavelength of the interrogating wave F _c , the transmission / reception PAA weight corresponding to the interrogation wave F _c is set to the weight table B, and the interval between the plurality of antenna elements 34 is set to 1 time the wavelength of the interrogating wave F _c The transmission / reception PAA weights corresponding to the cases are stored in the weight table C, respectively. Then, the PAA weight control unit 48 serving as a directivity control unit reads one of a plurality of weights stored in the weight memory unit 49 and sets a transmission / reception PAA weight based thereon. By selectively using such a transmission / reception PAA weight according to the element interval, an optimal directivity pattern can be formed when the element interval is changed according to the communication purpose. Thus, suitable communication can be realized. In this embodiment, the transmission weight used for transmission directivity control and the reception weight used for reception directivity control are set to a common value. However, there is an aspect in which different values are used for transmission and reception. Conceivable.

  FIG. 15 is a flowchart for explaining the search control operation of the wireless tag 14 by the wireless tag communication device 12, and is repeatedly executed at a predetermined cycle.

First, in step (hereinafter, step is omitted) SA1, a command bit string for the wireless tag 14 to be searched is generated by the command bit string generation unit 38, and is encoded by the FSK encoding unit 40 using the FSK method. The Next, in SA2, the signal encoded in SA1 is modulated by the AM modulation unit 42 by the AM method and stored in the transmission memory unit 44. Next, in SA3, θ = −30 ° is set as an initial value in the directivity direction in the transmission / reception PAA weight register, that is, the weight memory unit 49. Next, in SA4 corresponding to the operation of the element spacing detection unit 66, the wavelength of the interrogation wave F _c in which the element spacing in the array antenna 36 is transmitted according to the signal from the element position sensor 64 is ½ wavelength. It is determined whether the wavelength is 3/4 wavelength or 1 wavelength. If it is determined in SA4 that the element spacing in the array antenna 36 is ½ wavelength, in SA5, the weight table A in the weight memory unit 49 is selected, and then the processing in SA8 and subsequent steps is executed. The If it is determined in SA4 that the element spacing in the array antenna 36 is 3/4 wavelength, then in SA6, after the weight table B in the weight memory unit 49 is selected, the processing in SA8 and subsequent steps is executed. Is done. If it is determined in SA4 that the element spacing in the array antenna 36 is one wavelength, then in SA7, after the weight table C in the weight memory unit 49 is selected, the processes in SA8 and subsequent steps are executed. .

In the process of SA8, the data stored in SA2 is read from the transmission memory unit 44, and the transmission PAA weight based on the weight table selected in SA5, SA6, or SA7 in the transmission weight multiplication unit 46 is multiplied. After that, it is transmitted as an interrogation wave F _c from the array antenna 36 via the plurality of high frequency transmission / reception units 52. Next, at SA9, the received reply wave F _r returned from the radio tag 14 in response to the interrogating wave F _c transmitted in SA8 is by the array antenna 36, through the plurality of high-frequency transceiver 52 It is stored in the reception memory unit 54. Next, in SA10, the data stored in SA9 is read from the reception memory unit 54, and the reception PAA weight based on the weight table selected in SA5, SA6, or SA7 in the reception weight multiplication unit 56 is obtained. After being multiplied, they are synthesized by the synthesizer 86. Next, at SA11, the composite signal synthesized at SA10 is demodulated by the AM demodulator 58 by the AM method. Next, in SA12, the signal demodulated in SA11 is decoded by the FSK decoding unit 60 by the FSK method. Next, in SA13, it is determined whether or not the decrypted data decrypted in SA12 is normal. If the determination at SA12 is affirmative, the routine is terminated after confirming that the wireless tag 14 to be searched is found at SA14, but the determination at SA13 is negative. In SA15, after 10 ° is added to the main lobe direction θ set in the weight memory unit 49, in SA16, the directivity direction θ set in the weight memory unit 49 is larger than 30 °. Is judged. When the determination at SA16 is negative, the processing after SA8 is executed again. However, when the determination at SA16 is affirmative, the wireless tag 14 to be searched was not found at SA17. After this is confirmed, this routine is terminated. In the above processing, SA5, SA6, SA7, SA8, and SA10 correspond to the operation of the PAA weight control unit 48.

  As described above, according to this embodiment, the array antenna 36 includes a plurality of antenna elements 34 and can change the interval between at least two antenna elements 34 used for communication with the wireless tag 14. The communication direction with the wireless tag 14 is set by setting a weight for changing at least the phase of each of the signals corresponding to the antenna elements 34 according to the distance between the antenna elements 34 in the array antenna 36. Antenna element that is involved in communication with the wireless tag 14 since it includes a PAA weight control unit 48 (SA5, SA6, SA7, SA8, and SA10), which is a directivity control unit that controls power. 34 In addition to being able to arbitrarily control the directivity characteristics by changing the interval between them, a predetermined web is selected according to the interval. It can be determined communication directivity suitably by setting and. That is, it is possible to provide the wireless tag communication device 12 that can appropriately set the communication directivity with the wireless tag 14 according to the communication purpose.

  In addition, a weight memory unit 49 that is a storage unit that stores a plurality of predetermined weight tables for each interval between the antenna elements 34 is provided, and the PAA weight control unit 48 is stored in the weight memory unit 49. In addition, since any one set of weight tables is read and set according to the interval between the antenna elements 34 among the plurality of sets of weight tables, the antenna elements 34 involved in communication with the wireless tag 14 are set. Weights that match the distance between each other can be set in a practical manner.

  The PAA weight control unit 48 controls the communication directivity so that the main lobe in communication with the wireless tag 14 has a desired beam width. In this way, the beam width of the main lobe in communication with the wireless tag 14 can be suitably controlled.

  Further, since the array antenna 36 can mechanically change the distance between at least two antenna elements 34 used for communication with the wireless tag 14, the wireless antenna 14 is operated by a manual adjustment knob 32. The interval between the antenna elements 34 involved in communication with the tag 14 can be changed in a practical manner.

  In addition, since the device includes an element position sensor 64 that is a detection device that detects a distance between at least two antenna elements 34 used for communication with the wireless tag 14, the element position sensor 64 detects the position. The communication directivity with the wireless tag 14 can be controlled in a practical manner by the PAA weight control unit 48 according to the interval.

  The array antenna 36 can change the interval between at least two antenna elements 34 used to transmit a transmission signal to the wireless tag 14, and the PAA weight control unit 48 Since a predetermined transmission weight is set according to the interval between the antenna elements 34 in the antenna 36, the transmission directivity in communication with the wireless tag 14 can be suitably controlled.

  The array antenna 36 can change the interval between at least two antenna elements 34 used to receive a reception signal returned from the wireless tag 14, and the PAA weight control unit 48 can Since a predetermined reception weight is set according to the interval between the antenna elements 34 in the array antenna 36, the reception directivity in communication with the wireless tag 14 can be suitably controlled.

  The plurality of antenna elements 34 transmit and receive a transmission signal toward the wireless tag 14, and transmit and receive signals used for receiving a reply signal returned from the wireless tag 14 according to the transmission signal. Since the antenna element 34 is used, the configuration of the array antenna 36 can be simplified as much as possible, and the transmission directivity and the reception directivity in communication with the wireless tag 14 can be suitably controlled.

  Next, another preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, regarding the following description, the same code | symbol is attached | subjected about the part which is common in the above-mentioned Example, and the description is abbreviate | omitted.

  FIG. 16 is a diagram for explaining the configuration of an RFID tag communication apparatus 120 according to another embodiment of the present invention. As shown in FIG. 16, the RFID tag communication device 120 of this embodiment includes a motor 122 that is connected to the central gear 110 of the gear device 106 and rotationally drives the central gear 110. As the motor 122, a stepping motor or the like that rotates at a constant angle (rotation amount) according to an electrical signal is preferably used, and communication with the wireless tag 14 is performed via the gear device 106 that is a power transmission device. It functions as a power generator for mechanically changing the distance between at least two antenna elements 34 used in the above. In addition, an element interval setting unit 123 that controls (sets) the interval between the plurality of antenna elements 34 by controlling the rotation amount of the motor 122 is functionally provided.

The RFID tag communication apparatus 120 is configured such that the operation mode, that is, the communication mode of the array antenna 36 can be set to any one of a wide beam, a middle beam, and a narrow beam. This wide beam corresponds to the case where the interval between the antenna elements 34 in the array antenna 36 is ½ times the wavelength of the interrogation wave F _c , and the middle beam is the mutual antenna element 34 in the array antenna 36. the spacing between corresponding when 3/4 times the wavelength of the interrogating wave F _c, narrow beam 1 times the wavelength of the interrogating wave F _c the spacing between the antenna elements 34 mutually in the array antenna 36 It corresponds to the case. The element interval setting unit 123 controls the number of rotations of the motor 122 by a predetermined operation via the operation unit 24 or automatic control according to a communication state with the wireless tag 14 to be communicated. The distance between the antenna elements 34 is changed to establish one of the operation modes of the wide beam, middle beam, and narrow beam. In the present embodiment, the mode in which the operation mode is changed to three stages will be described. However, the operation mode may be changed to two stages, or may be changed to four or more stages.

Here, the RFID tag communication apparatus 120 is preferably configured such that when the interval between the antenna elements 34 is less than a predetermined value, for example, less than 3/4 times the wavelength of the interrogation wave F _c. the while changing the directivity by PAA weight control section 48 performs communication with the wireless tag 14, the antenna element 34 interval between each other than a predetermined value, for example of the wavelength of the interrogating wave F _c 3 / If it is four times or more, the directivity set by the PAA weight control unit 48 is fixed and communication with the wireless tag 14 is performed. As described above, when the distance between the antenna elements 34 is relatively narrow, the communication mode by the array antenna 36 is a wide beam, and the position of the wireless tag 14 in a wide search range is roughly detected. Is preferable. In such an aspect, the target wireless tag 14 can be retrieved more quickly by changing the directivity by the PAA weight control unit 48 which is a directivity control unit. On the other hand, when the distance between the antenna elements 34 is relatively wide, the communication mode by the array antenna 36 is a narrow beam, and the position where the wireless tag 14 whose rough position is known is obtained in detail. Is preferable. In such an aspect, the directivity is fixed by the PAA weight control unit 48 which is a directivity control unit, and a suitable communication is realized by, for example, the user holding and shaking the RFID tag communication device 120 by hand. it can.

  In the RFID tag communication apparatus 120, preferably, the RFID tag 14 to be searched is temporarily searched in a state where the distance between the antenna elements 34 in the array antenna 36 is relatively narrow, and the antenna elements 34 are detected. The main search of the wireless tag 14 is performed in a state where the interval between each other is relatively wide. For example, a temporary search is performed with the communication mode of the array antenna 36 as a wide beam (that is, the element interval is ½ wavelength), and the main search is performed with the communication mode as a narrow beam (that is, the element interval is one wavelength). As described above, the wide beam is suitable for the communication for searching for the approximate position of the wireless tag 14, and the narrow beam is suitable for the communication for searching for the detailed position of the wireless tag 14. By performing the temporary search and the main search by appropriately setting the communication directivity of the array antenna 36, the position where the wireless tag 14 to be communicated can be searched as quickly as possible.

  FIG. 17 is a flowchart for explaining the search control operation of the wireless tag 14 by the wireless tag communication device 120, which is repeatedly executed at a predetermined cycle. In the control shown in FIG. 17, steps common to the control shown in FIG. 15 described above are denoted by the same reference numerals, and description thereof is omitted.

In the control shown in FIG. 17, it is determined whether the operation mode of the RFID tag communication device 12 is wide beam, middle beam, or narrow beam in SA18 following the processing of SA2 described above. If it is determined in SA18 that the operation mode of the RFID tag communication device 12 is wide beam, in SA19, the motor 122 is driven and the element spacing in the array antenna 36 is set to ½ wavelength. In SA5, after the weight table A in the weight memory unit 49 is selected, the processes in SA3 and subsequent steps are executed. If it is determined in SA18 that the operation mode of the RFID tag communication device 12 is middle beam, the motor 122 is driven so that the element spacing in the array antenna 36 is 3/4 wavelength, and SA6 , After the weight table B is selected in the weight memory unit 49, the processing from SA3 onward is executed. If it is determined in SA18 that the operation mode of the RFID tag communication device 12 is a narrow beam, in SA21, the motor 122 is driven and the element interval in the array antenna 36 is set to one wavelength. In SA7, after the weight table C in the weight memory unit 49 is selected, the processing after SA3 is executed. Further, if the determination of SA13 described above is yes, SA13 ', the spacing between the antenna elements 34 mutually whether one wavelength of the wavelength of the interrogating wave F _c is determined. If the determination at SA13 ′ is negative, the above-described processing after SA15 is executed. If the determination at SA13 ′ is affirmative, it is determined at SA13 ″ whether the search is interrupted. When the determination of SA13 ″ is affirmed, the above-described processing after SA17 is executed, but when the determination of SA13 ″ is negative, the above-described processing after SA8 is executed again. In the above control, SA19, SA20, and SA21 correspond to the operation of the element interval setting unit 123.

  FIG. 18 is a flowchart for explaining another example of the search control operation of the wireless tag 14 by the wireless tag communication device 120, which is repeatedly executed at a predetermined cycle.

First, in S1, the command bit string generation unit 38 generates a command bit string for the wireless tag 14 to be searched, and the FSK encoding unit 40 encodes the command bit string using the FSK method. Next, in S <b> 2, the signal encoded in S <b> 1 is modulated by the AM modulation unit 42 by the AM method and stored in the transmission memory unit 44. Next, in S3, the spacing between antenna elements 34 mutually in the array antenna 36 the motor 122 is driven to 1/2 times the wavelength of the interrogating wave F _c. Next, in S4, the weight table A in the weight memory unit 49 is selected. Next, in ST, tag temporary search control detailed in FIG. 19 is executed. Next, in S5, the spacing between antenna elements 34 mutually in the array antenna 36 the motor 122 is driven to a 1 times the wavelength of the interrogating wave F _c. Next, in S6, the weight table C in the weight memory unit 49 is selected. Next, in the SM, the regular tag search control detailed in FIG. 20 is executed, and then this routine is terminated.

FIG. 19 is a flowchart for explaining the temporary tag search control which is a part of the wireless tag search control shown in FIG. In the control shown in FIG. 19, first, in ST1, θ = −30 ° is set as the initial value in the directivity direction in the transmission / reception PAA wait register, that is, the weight memory unit 49. Next, after the data stored in S2 is read from the transmission memory unit 44 in ST2 and the transmission PAA weight based on the weight table A selected in S4 is multiplied by the transmission weight multiplication unit 46, Are transmitted as interrogation waves F _c from the array antenna 36 via the plurality of high-frequency transmission / reception units 52. Next, in ST 3, the response wave F _r returned from the wireless tag 14 in response to the interrogation wave F _c transmitted in ST 2 is received by the array antenna 36, and passes through the plurality of high frequency transmission / reception units 52. It is stored in the reception memory unit 54. Next, in ST4, after the data stored in ST3 is read from the reception memory unit 54, the reception weight multiplication unit 56 multiplies the reception PAA weight based on the weight table A selected in S4. Are synthesized by the synthesizer 86. Next, in ST5, the synthesized signal synthesized in ST4 is demodulated by the AM demodulator 58 by the AM method. Next, in ST6, the amplitude A of the AM demodulated signal demodulated in ST5 is detected. Next, in ST7, it is determined whether or not the amplitude A detected in ST6 is the maximum. If the determination in ST7 is affirmative, in ST8, the detected amplitude A is substituted for A _{temp_max} indicating the maximum amplitude, and the main lobe direction θ at that time is substituted for θ _{temp_max} indicating the maximum sensitivity direction. Thereafter, the processing from ST9 onward is executed. If the determination in ST7 is negative, in ST9, 30 ° is added to the main lobe direction θ set in the weight memory unit 49, and then in ST10. Then, it is determined whether or not the main lobe direction θ set in the weight memory unit 49 is larger than 30 °. If the determination in ST10 is negative, the processing from ST2 _onward is executed again. If the determination in ST10 is positive, whether A _{temp_max} indicating the maximum amplitude is greater than or equal to a predetermined required value. Is judged. If the determination in ST11 is negative, the routine is terminated after it is confirmed in ST12 that the wireless tag 14 to be searched has not been found, but the determination in ST11 is positive Then, the radio tag search control shown in FIG. 18 is restored.

FIG. 20 is a flowchart for explaining the actual tag search control which is a part of the RFID tag search control shown in FIG. In the control shown in FIG. 20, first, in SM1, θ = θ _temp — _max −10 ° is set in the weight memory unit 49 as an initial value in the main lobe direction. Next, in SM2, the data stored in S2 is read from the transmission memory unit 44, and the transmission weight multiplication unit 46 multiplies the transmission PAA weight based on the weight table C selected in S6. Are transmitted as interrogation waves F _c from the array antenna 36 via the plurality of high-frequency transmission / reception units 52. Next, the SM3, received reply wave F _r returned from the radio tag 14 in response to the interrogating wave F _c transmitted in SM2 is by the array antenna 36, through the plurality of high-frequency transceiver 52 It is stored in the reception memory unit 54. Next, in SM4, after the data stored in SM3 is read from the reception memory unit 54, the reception weight multiplication unit 56 multiplies the reception PAA weight based on the weight table C selected in S6. Are synthesized by the synthesizer 86. Next, in SM5, the synthesized signal synthesized in SM4 is demodulated by the AM demodulator 58 by the AM method. Next, in SM6, the amplitude of the AM demodulated signal demodulated in SM5 is detected, and it is determined whether or not the amplitude is maximum. If the determination of SM6 is affirmative, in SM7, the main lobe direction θ at that time is substituted for θ _max indicating the tag direction, and then the processing from SM8 is executed, but the determination of SM6 is negative. In SM8, after 10 ° is added to the main lobe direction θ set in the weight memory unit 49 in SM8, in SM9, the main lobe direction θ set in the weight memory unit 49 becomes θ _{temp_max} It is determined whether the angle is greater than + 10 °. If the determination of SM9 is negative, the processing subsequent to SM2 is executed again. However, if the determination of SM9 is positive, there is a wireless tag 14 whose search target is θ _max at that time. After confirming that the direction is the direction, the radio tag search control shown in FIG. 18 is restored.

  As described above, according to the present embodiment, the motor 122 which is a power generator for mechanically changing the distance between at least two antenna elements 34 used for communication with the wireless tag 14 and the power Since the gear device 106 which is a transmission device is provided, the distance between the antenna elements 34 involved in communication with the wireless tag 14 via the gear device 106 by driving the motor 122 is practical. The mode can be changed.

  In addition, when the interval between the antenna elements 34 is less than a predetermined value, that is, not one wavelength, the wireless tag communication device 120 changes the directivity by the PAA weight control unit 48 and changes the directivity. 14, when the distance between the antenna elements 34 is equal to or greater than a predetermined value, that is, one wavelength, the directivity set by the PAA weight control unit 48 is fixed and the antenna element 34 is fixed. Since communication is performed with the wireless tag 14, communication with the wireless tag can be performed in a suitable manner in accordance with directivity characteristics corresponding to the distance between the antenna elements 34.

  FIG. 21 is a diagram for explaining the configuration of an RFID tag communication apparatus 124 that is still another embodiment of the present invention. As shown in FIG. 21, the RFID tag communication apparatus 124 of this embodiment includes a plurality of (seven in FIG. 21) antenna elements 34a, 34b, 34c, 34d, 34e, which are erected so as to be parallel to each other. An array antenna 126 having 34 f and 34 g (hereinafter simply referred to as an antenna element 34 unless otherwise distinguished) is provided. Further, any one of the antenna elements 34a, 34b, 34c is selectively connected to the high frequency transmitting / receiving unit 52a so as to be able to input / output, and any one of the antenna elements 34e, 34f, 34g is selectively connected to the high frequency transmitting / receiving unit. Communication between the wireless tag 14 by controlling the connection between the plurality of antenna elements 34 and the high-frequency transmitting / receiving unit 52 by the antenna selection unit 128 connected to the input / output 52c so as to allow input / output. And an element interval setting unit 130 for setting an interval between the antenna elements 34 used in the above.

FIG. 22 is a diagram illustrating the relative positional relationship of the plurality of antenna elements 34 in the array antenna 126. As shown in FIG. 22, the position the array antenna 126, that are separated one times the distance of the wavelength of the antenna elements 34a and 34g are the interrogating wave F _c from the antenna element 34a around the antenna element 34d, 3/4 times the distance between each position of the wavelength of the interrogating wave _{F c} the antenna elements 34b and 34f from the antenna element 34a, the wavelength of the interrogating wave _{F c} the antenna elements 34c and 34e from the antenna element 34a Are disposed at positions at a distance of 1/2 times the distance. Further, when the antenna selection unit 128 connects the antenna element 34a to the high frequency transmission / reception unit 52a, the antenna selection unit 128 connects the antenna element 34g to the high frequency transmission / reception unit 52c, and connects the antenna element 34b to the high frequency transmission / reception unit 52a. In this case, when the antenna element 34f is connected to the high frequency transmitter / receiver 52c and the antenna element 34c is connected to the high frequency transmitter / receiver 52a, the antenna element 34e is connected to the high frequency transmitter / receiver 52c. That is, in the array antenna 126, the antenna element 34b is in a first state in which the antenna elements 34a, 34d, and 34g are selected as a plurality of antenna elements that transmit and receive information to and from the wireless tag 14 that is a communication target. , 34d, 34f and the third state where the antenna elements 34c, 34d, 34e are selected are selectively established. As described above, the array antenna 126 communicates with the wireless tag 14 by selecting at least two antenna elements 34 used for communication with the wireless tag 14 from the plurality of antenna elements 34. The interval between the antenna elements 34 used in the above is changed.

Here, in the first state in which the antenna elements 34a, 34d, and 34g are selected as a plurality of antenna elements that transmit and receive information to and from the wireless tag 14 that is a communication target, the distance between the antenna elements 34 is determined. Becomes one time the wavelength of the interrogation wave _Fc , and the communication mode by the array antenna 36 becomes relatively sharp (narrow beam). Further, the antenna elements 34b, 34d, in the second state 34f is selected, the interval between those antenna elements 34 mutually becomes 3/4 times the wavelength of the interrogating wave _{F c,} the communication mode by the array antenna 36 Is in the middle (middle beam). Further, the antenna element 34c, in a third state 34d, 34e are selected, the spacing between the antennas elements 34 each other to 1/2 times the wavelength of the interrogating wave _{F c,} the communication mode by the array antenna 36 Is relatively wide (wide beam). In addition, the PAA weight control unit 48 provided in the RFID tag communication device 124 stores the weight memory unit 49 in accordance with the interval between the antenna elements 34 in the array antenna 126 as in the above-described embodiment. Corresponding weights are read from a plurality of stored weights, and the transmission PAA weight multiplied by the transmission weight multiplication unit 46 and the reception PAA weight multiplied by the reception weight multiplication unit 56 are controlled based on the weights.

  FIG. 23 is a flowchart for explaining the search control operation of the wireless tag 14 by the wireless tag communication device 124, which is repeatedly executed at a predetermined cycle. In the control shown in FIG. 23, steps common to the control shown in FIG. 15 described above are denoted by the same reference numerals, and description thereof is omitted.

  In the control shown in FIG. 23, it is determined whether the operation mode of the RFID tag communication device 12 is wide beam, middle beam, or narrow beam in SA18 following the processing of SA3 described above. If it is determined in SA18 that the operation mode of the RFID tag communication device 12 is wide beam, in SA22, the antenna element 34c is connected to the high frequency transmitter / receiver 52a, and the antenna element 34d is connected to the high frequency transmitter / receiver 52b. The antenna element 34e is connected to the high-frequency transmitting / receiving unit 52c so that the element spacing in the array antenna 36 is ½ wavelength. In SA5, after the weight table A in the weight memory unit 49 is selected, SA8 or less Processing is executed. If it is determined in SA18 that the operation mode of the RFID tag communication device 12 is middle beam, in SA23, the antenna element 34b is connected to the high frequency transmitter / receiver 52a, and the antenna element 34d is connected to the high frequency transmitter / receiver 52b. The antenna element 34f is connected to the high-frequency transmitting / receiving unit 52c, respectively, so that the element spacing in the array antenna 36 is 3/4 wavelength. After the weight table B in the weight memory unit 49 is selected in SA6, SA8 or less The process is executed. If it is determined in SA18 that the operation mode of the RFID tag communication device 12 is a narrow beam, the antenna element 34a is in the high frequency transmitting / receiving unit 52a and the antenna element 34d is in the high frequency transmitting / receiving unit 52b in SA24. The antenna element 34g is connected to the high-frequency transmitting / receiving unit 52c so that the element interval in the array antenna 36 is one wavelength. In SA7, the weight table C in the weight memory unit 49 is selected, and then the processing in SA8 and subsequent steps. Is executed. In the above control, SA22, SA23, and SA24 correspond to the operation of the antenna selection unit 128.

  Thus, according to the present embodiment, the array antenna 126 includes three or more antenna elements 34, and at least used for communication with the wireless tag 14 among the antenna elements 34. Since the antenna selection unit 128 (SA22, SA23, and SA24) for selecting the two antenna elements 34 is provided, the interval between the antenna elements 34 involved in communication with the wireless tag 14 is practical. Can be changed in various ways.

  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 transmission weight multiplication unit 46, the PAA weight control unit 48, the reception weight multiplication unit 50, the element interval detection unit 66, and the like are provided as individual control devices. These control functions may be functionally provided in a DSP (Digital Signal Processor) that executes digital signal processing including a CPU, ROM, RAM, and the like. Moreover, it does not ask | require whether the control operation | movement by these control functions is based on a digital signal process and is based on an analog signal process.

  In the above-described embodiment, the mode of controlling the communication directivity with the wireless tag 14 by PAA (Phased Array Antenna) processing has been described. For example, the wireless tag is processed by AAA (Adaptive Array Antenna) processing or the like. The present invention is also suitably applied to a wireless tag communication device that can control the communication directivity with the communication device 14.

  In the above-described embodiment, the portable wireless tag communication device 12 that can be carried and used by the user for communication with the wireless tag 14 has been described. The present invention is also preferably applied to a stationary wireless tag communication apparatus.

  Further, in the above-described embodiment, the present invention is applied to both the transmission directivity control of the transmission signal and the reception directivity control of the reception signal. However, the present invention is applied to at least one of them. Since a temporary effect is obtained, the present invention may not necessarily be applied to both transmission and reception.

  In the above-described embodiment, the transmission / reception antenna element used for transmitting a transmission signal toward the wireless tag 14 and receiving a return signal returned from the wireless tag 14 according to the transmission signal. Although the RFID tag communication device 12 and the like provided with the array antenna 36 for transmission / reception provided with 34 has been described, a transmission antenna for transmitting the transmission signal and a reception antenna for receiving the reception signal are separately provided. The present invention is also suitably applied to a wireless tag communication device.

  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 with which the radio | wireless tag communication apparatus of this invention is used suitably. It is a top view explaining the external appearance of the RFID tag communication apparatus which is one Example of this invention. FIG. 3 is a rear view of the wireless tag communication device of FIG. 2 as viewed from the direction of arrow III. It is a figure explaining the structure of the radio | wireless tag communication apparatus of FIG. FIG. 5 is a diagram illustrating in detail a configuration of a transmission weight multiplying unit in FIG. 4. It is a figure explaining the structure of the high frequency transmission / reception part of FIG. 4 in detail. FIG. 5 is a diagram illustrating in detail a configuration of a reception weight multiplication unit in FIG. 4. It is a figure explaining the structure of the RFID circuit element with which the RFID tag which is the communication object of the RFID tag communication apparatus of this invention was equipped. It is a figure explaining the change of the space | interval between antenna elements in the antenna unit of the radio | wireless tag communication apparatus of FIG. 2, and has illustrated the case where the element space | interval was made comparatively wide. It is a figure explaining the change of the space | interval between antenna elements in the antenna unit of the radio | wireless tag communication apparatus of FIG. 2, and has illustrated the case where an element space | interval was made comparatively narrow. FIG. 10 is a partial cross-sectional view illustrating in detail an enlarged internal configuration of a portion surrounded by an alternate long and short dash line in the antenna unit shown in FIG. 9, and shows a gear device for changing the extension dimension from a unit base of a pair of support arms. ing. It is a figure explaining the difference in the directivity pattern by the space | interval between antenna elements in the RFID tag communication apparatus of FIG. 2, and has illustrated the directivity pattern of directivity direction (theta) = 0 degree. It is a figure explaining the difference in the directivity pattern by the space | interval between antenna elements in the RFID tag communication apparatus of FIG. 2, and has illustrated the directivity pattern of directivity direction (theta) = 30 degrees. FIG. 5 is a diagram illustrating a plurality of sets of weights stored in a weight memory unit in FIG. 4. 5 is a flowchart for explaining an RFID tag search control operation by the RFID tag communication apparatus of FIG. It is a figure explaining the structure of the RFID tag communication apparatus which is the other Example of this invention. FIG. 17 is a flowchart for explaining an RFID tag search control operation by the RFID tag communication apparatus of FIG. 17 is a flowchart for explaining another example of the RFID tag search control operation by the RFID tag communication apparatus of FIG. It is a flowchart explaining the tag temporary search control which is a part of RFID tag search control shown in FIG. FIG. 19 is a flowchart describing tag main search control that is part of the wireless tag search control shown in FIG. 18. FIG. It is a figure explaining the structure of the radio | wireless tag communication apparatus which is another Example of this invention. It is a figure which illustrates the relative positional relationship of the some antenna element in the array antenna with which the RFID tag communication apparatus of FIG. 21 was equipped. It is a flowchart explaining the RFID tag search control operation | movement by the RFID tag communication apparatus of FIG.

Explanation of symbols

12, 120, 124: RFID tag communication device 14: RFID tag 34: antenna element 36, 126: array antenna 48: PAA weight control unit (directivity control unit)
49: Wait memory unit (storage unit)
64: Element position sensor (detection device)
106: Gear device (power transmission device)
122: Motor (power generator)
128: Antenna selector

Claims (11)

A wireless tag communication device that transmits a transmission signal to a wireless tag, receives a return signal returned from the wireless tag according to the transmission signal, and communicates information with the wireless tag. ,
An array antenna having a plurality of antenna elements and capable of changing a distance between at least two antenna elements used for communication with the wireless tag;
Directivity for controlling communication directivity with the wireless tag by setting a weight for changing at least the phase of each of the signals corresponding to the antenna elements in accordance with the distance between the antenna elements in the array antenna. A wireless tag communication device comprising: a wireless control unit.   A storage unit configured to store a plurality of sets of weight tables determined in advance for each interval between the antenna elements, and the directivity control unit includes the plurality of sets of weight tables stored in the storage unit. 2. The wireless tag communication apparatus according to claim 1, wherein any one set of weight tables is read and set according to the interval.   3. The wireless tag communication device according to claim 1, wherein the directivity control unit controls the communication directivity so that a main lobe in communication with the wireless tag has a desired beam width.   4. The wireless tag communication device according to claim 1, wherein the array antenna can mechanically change a distance between at least two antenna elements used for communication with the wireless tag.   5. The wireless tag communication device according to claim 4, further comprising a power generator and a power transmission device for mechanically changing a distance between at least two antenna elements used for communication with the wireless tag.   6. The wireless tag communication device according to claim 1, further comprising a detection device that detects an interval between at least two antenna elements used for communication with the wireless tag.   The array antenna includes three or more antenna elements, and includes an antenna selection unit that selects at least two antenna elements used for communication with the wireless tag among the antenna elements. The wireless tag communication device according to any one of claims 1 to 3.   The array antenna can change a distance between at least two antenna elements used for transmitting a transmission signal to the wireless tag, and the directivity control unit is configured so that the antenna elements in the array antenna 8. The wireless tag communication device according to claim 1, wherein a predetermined transmission weight is set according to an interval between the wireless tag communication devices.   The array antenna is capable of changing an interval between at least two antenna elements used for receiving a reception signal returned from the wireless tag, and the directivity control unit includes the array antenna in the array antenna. 9. The wireless tag communication device according to claim 1, wherein a predetermined reception weight is set according to an interval between the antenna elements.   When the distance between the antenna elements is less than a predetermined value, the directivity control unit performs communication with the wireless tag while changing the directivity, and the distance between the antenna elements is a predetermined value. In the case described above, the RFID tag communication apparatus according to any one of claims 1 to 9, wherein communication with the RFID tag is performed with the directivity set by the directive control unit fixed.   The plurality of antenna elements are transmitting / receiving antenna elements used for transmitting a transmission signal toward the wireless tag and receiving a return signal returned from the wireless tag in response to the transmission signal. Item 11. The wireless tag communication device according to any one of Items 1 to 10.

Images