JP2007221557A - Interrogator in wireless tag communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interrogator in a wireless tag communication system for improving the information transmission/reception accuracy, by decreasing the reception disturbance due to intrusion of a transmission wave from a transmission antenna to a reception antenna. <P>SOLUTION: The interrogator includes transmission antenna elements 1a to 1c for transmitting a signal containing at least a carrier to a radio tag circuit element To provided with an IC circuit section 150 and a tag side antenna 151 in a non-contact manner to access the IC circuit section 150; and receiving antenna elements 1d to 1f provided separately from the transmission antenna elements 1a to 1c and receiving a reply signal returned from the IC circuit section 150 in a non-contact manner, according to the signal transmitted from the transmission antenna elements 1a to 1c, and the transmitting antenna elements 1a to 1c and the receiving antenna elements 1d to 1f are arranged, to be located in regions where the gains of the antenna elements become almost minimum to each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an interrogator of a wireless tag communication system that reads information from a wireless tag circuit element capable of wireless communication of information with the outside.

  2. Description of the Related Art An RFID (Radio Frequency Identification) system that reads / writes information of a wireless tag by transmitting and receiving an inquiry and receiving a reply from a reader / writer without contact with a small wireless tag is known.

  For example, a wireless tag circuit element included in a label-like wireless tag includes an IC circuit unit that stores predetermined wireless tag information and an antenna that is connected to the IC circuit unit and transmits / receives information. When a transmission wave is transmitted from a transmission antenna of a reader / writer as an interrogator to a wireless tag as a responder, the wireless tag circuit element transmits a response using the energy of the radio wave of the transmission wave. That is, when the reader / writer transmits radio waves, the radio wave from the wireless tag returned almost simultaneously is received by the receiving antenna of the reader / writer. At this time, since the attenuation (transmission / reception separation) of the radio wave between the transmission antenna and the reception antenna in the reader / writer is finite, the transmission signal is inevitably received and mixed by the reception system from the reception antenna. Thus, the reception of the response signal from the wireless tag is disturbed.

Here, in order to solve such transmission / reception interference, as a conventional technique of a general wireless communication device, for example, one described in Patent Document 1 has already been proposed. In this prior art, a transmission signal in one polarization direction is transmitted from one wireless communication device and received by the other wireless communication device, and a response signal in a polarization direction different from the above is transmitted from the other wireless communication device accordingly. Received by one wireless communication device. In this way, by changing the polarization direction of transmission from one side → reception (outgoing) on the other side, transmission from the other side → reception (returning) on the other side, transmission in the wireless communication apparatus that first transmitted (one) The polarization direction of the signal and that of the response signal are different from each other, so that interference of the transmission signal (= reception interference) upon reception of the response signal is prevented.
Japanese Patent Laid-Open No. 54-121093

  However, when trying to apply the configuration of the above prior art to a communication system using the above-described wireless tag, there are the following problems.

  That is, if different polarizations as described above are used for communication (outgoing and replying) between the reader / writer as the interrogator and the RFID circuit element as the responder, they differ on the RFID circuit element side. A complicated configuration (large and special antenna) corresponding to two polarization directions is required, and it is difficult to actually realize such a configuration in a limited-size wireless tag.

  An object of the present invention is to provide an interrogator for an RFID tag communication system that can reduce reception interference due to mixing of transmission waves from a transmission antenna to a reception antenna and can improve information transmission / reception accuracy.

  In order to achieve the above object, a first invention provides a signal including at least a carrier wave with respect to an RFID circuit element including an IC circuit unit for storing predetermined information and a tag-side antenna connected to the IC circuit unit. Is transmitted in a contactless manner, and a transmission antenna that accesses the IC circuit unit, and a response signal provided separately from the transmission antenna and returned from the IC circuit unit in response to the signal transmitted by the transmission antenna. The transmission antenna and the reception antenna are arranged so as to be positioned in a direction in which the gain is substantially minimum.

  A signal including a carrier wave is transmitted from the transmission antenna to the RFID circuit element, and the IC circuit portion of the RFID circuit element is accessed without contact. A response signal returned in response to the signal is received by the receiving antenna in a non-contact manner, and information is transmitted to and received from the RFID circuit element. At this time, the amount of radio wave attenuation (transmission / reception separation) between the transmission antenna and the reception antenna is finite, so if the transmission wave is received and mixed by the reception antenna, it becomes an interference signal from the RFID circuit element. There is a possibility of disturbing reception of the response signal.

  In the first invention of the present application, the transmitting antenna and the receiving antenna are arranged in a direction (so-called null direction) in which the gain is substantially minimum. As a result, the transmission wave hardly reaches the reception antenna when viewed from the transmission antenna side, and the transmission wave is not received since there is almost no gain when viewed from the reception antenna side. As a result, reception interference due to mixing of transmission waves from the transmission antenna to the reception antenna can be reduced, and information transmission / reception accuracy can be improved.

  A second invention is characterized in that, in the first invention, the transmitting antenna and the receiving antenna are dipole antennas extending substantially in a straight line.

  Dipole antennas are used as the transmitting antenna and the receiving antenna. For example, by arranging these dipole antennas so that the axis lines of the elements are substantially aligned with each other, it is possible to achieve an arrangement in which the gains are substantially minimized. Reception interference due to mixing of transmission waves from the transmission antenna to the reception antenna can be reduced.

  A third invention is characterized in that, in the first invention, the transmitting antenna and the receiving antenna are array antennas comprising a plurality of antenna elements.

  For example, in the case of a dipole antenna, the antenna elements constituting the array antenna are arranged so that the axes of the antenna elements are substantially in a straight line between the transmitting side and the receiving side. Can be reduced so that reception interference due to mixing of transmission waves from the transmission antenna to the reception antenna can be reduced.

  A fourth invention is characterized in that, in the third invention, the arrangement interval between the plurality of antenna elements of the transmission antenna and the arrangement interval between the plurality of antenna elements of the reception antenna are different from each other. To do.

  Since the resolution can be improved as the distance between the antenna elements is increased, the resolution can be different between the transmission side and the reception side by making the arrangement interval between the antenna elements different between the transmission side and the reception side. .

  A fifth invention is characterized in that, in the fourth invention, the arrangement interval between the plurality of antenna elements of the receiving antenna is made larger than the arrangement interval between the plurality of antenna elements of the transmission antenna.

  Thereby, the resolution on the receiving side can be made larger than the resolution on the transmitting side.

  According to a sixth invention, in any one of the third to fifth inventions, the transmitting antenna or the receiving antenna has each of the plurality of antenna elements arranged along a curved surface having a predetermined curvature. Features.

  When a plurality of antenna elements are arranged on a substantially flat surface, the sensitivity decreases as the antenna elements are located on both ends from the antenna element located on the center side. In the sixth invention of the present application, by arranging each antenna element along a curved surface having a predetermined curvature, by appropriately setting the direction and curvature of the curved surface, the above-described adverse effects can be avoided and the antenna elements are substantially equivalent to each other. Communication conditions can be set.

  In a seventh aspect based on the first aspect, the transmitting antenna and the receiving antenna are planar antennas.

  A planar antenna is used as a transmitting antenna and a receiving antenna. For example, by arranging these planar antennas so that they are substantially on the same plane or curved surfaces, it is possible to achieve an arrangement in which the gain is substantially minimized. Reception interference due to mixing of transmission waves from the antenna to the reception antenna can be reduced.

  In an eighth aspect based on the seventh aspect, the plurality of transmission antennas and the plurality of reception antennas are arranged on substantially the same plane, and the transmission antennas and the reception antennas are alternately arranged in a staggered pattern on the plane. It is arranged.

  When a plurality of planar antennas on the transmission side and a plurality of planar antennas on the reception side are arranged in a staggered pattern on substantially the same plane, the communicable area seen on the transmission side (existence range of RFID circuit elements that can reach the transmission signal) And the communicable range (existing range of the RFID tag circuit element capable of receiving the response signal) viewed on the receiving side can be further widened. As a result, the communication range seen in the entire interrogator can be further increased.

  According to a ninth aspect, in the seventh aspect, the plurality of transmitting antennas or the plurality of receiving antennas are arranged along a curved surface having a predetermined curvature.

  By arranging the transmitting and receiving antennas, which are planar antennas, along a curved surface with a predetermined curvature, the direction and curvature of the curved surface are set appropriately, so that almost the same communication can be performed for any antenna regardless of the position on the curved surface. It becomes possible to make it a condition.

  A tenth invention is characterized in that, in the sixth or eighth invention, the radius of curvature of the curved surface is set according to a maximum communication distance.

  Since the antenna element or planar antenna arranged on the curved surface is substantially the same distance (= curvature radius) to the center of curvature, by setting this radius of curvature corresponding to the maximum communication distance, which antenna element or With respect to the planar antenna, good communication up to the maximum communication distance can be surely ensured under substantially equivalent communication conditions.

  ADVANTAGE OF THE INVENTION According to this invention, the reception interference by mixing of the transmission wave from a transmitting antenna to a receiving antenna can be reduced, and information transmission / reception accuracy can be improved.

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

  FIG. 1 is a system configuration diagram illustrating an overall outline of a wireless tag communication system to which the first embodiment is applied.

  In FIG. 1, the RFID tag communication system S includes an interrogator 100 according to the present embodiment and a plurality of RFID tags T as responders corresponding to the interrogator 100.

  The wireless tag T includes a wireless tag circuit element To including an antenna 151 and an IC circuit unit 150.

  In this example, the interrogator 100 accesses an array-type antenna unit 1 composed of six antenna elements 1a to 1f, which will be described later, and the IC circuit unit 150 of the RFID circuit element To via this antenna unit 1 (this In the example, the high-frequency circuit 2 for reading), the signal processing circuit 3 for processing the signal read from the RFID circuit element To, and the RFID circuit element To through the antenna 1 and the high-frequency circuit 2 The information is read from the RFID circuit element To via the display section 4 for displaying the information read from the display, the database (abbreviated as DB in the figure) 5 for storing and holding the read information, and the signal processing circuit 3. A central control unit 6 for processing the signal and connected to the display unit 4 and the database 5 and controlling the entire interrogator 100 is provided.

  The central control unit 6 is a so-called microcomputer, and although not shown in detail, the central control unit 6 includes a central processing unit such as a CPU, a ROM, and a RAM. The central control unit 6 stores in advance in the ROM while using a temporary storage function of the RAM. The signal processing is performed according to the programmed program.

  FIG. 2 is a functional block diagram showing a detailed configuration of the antenna unit 1 in the interrogator in the present embodiment. The antenna unit 1 is shown as viewed from the front of the same plane where the antenna elements 1a to 1f are arranged.

  Each antenna element 1a to 1f is connected to a balun 12 connected to a high-frequency transmitter 34A, 34B, 34C or a high-frequency receiver 35A, 35B, 35C, which will be described later, via the coaxial feeder 11, and connected to the balun 12 in the same straight line. The two antenna wires 13 are integrated to form a centrally fed dipole antenna extending in a substantially straight line (details will be described later). The three antenna elements (transmission antennas) 1a to 1c in this example are provided in a substantially parallel arrangement while being separated from each other by the first interval δ1 to constitute a transmission array antenna portion (array antenna) 1A. In addition, the other three antenna elements (reception antennas) 1d to 1f in this example are provided in a substantially parallel arrangement while being separated from each other by a second interval δ2 larger than the first interval δ1. Antenna) 1B.

  The longitudinal direction D1 of the entire transmitting array antenna unit 1A (that is, the separating direction between the antenna elements 1a to 1c) and the longitudinal direction D2 of the entire receiving array antenna unit 1B (that is, the separating direction of the antenna elements 1d to 1f) are substantially the same. All the antenna elements 1a to 1f are arranged in parallel to each other and arranged in parallel to the antenna unit 1 in an arrangement that is substantially parallel to each other and located on substantially the same plane.

  The transmission array antenna unit 1A transmits a signal (= interrogation wave) including at least a carrier wave by wireless communication to the antenna 151 of the RFID circuit element To, and the reception array antenna unit 1B is transmitted from the transmission array antenna unit 1A. The radio tag circuit element To responds to the transmitted signal and receives and outputs a signal (= response wave). In each case, directivity control described later is performed in this example, and the radiation pattern (direction of the main lobe) of the antenna unit 1 as a whole is controlled electronically.

  In such an arrangement, the antenna elements 1d to 1f of the receiving array antenna unit 1B are configured to transmit the signal radiation patterns from the antenna elements 1a to 1c of the transmitting array antenna unit 1A (only the antenna element 1b is illustrated). It is outside the range R of the main lobe of each antenna element 1a to 1c of the antenna unit 1A and is almost in the null direction N. Conversely, the positional relationship between the signal radiation patterns from the antenna elements 1d to 1f of the receiving array antenna section 1B (only the antenna element 1e is illustrated) and the antenna elements 1a to 1c of the transmitting array antenna section 1B is also shown. The same relationship is obtained.

  FIG. 3 is a diagram illustrating a detailed configuration of the antenna elements 1a to 1f.

  Here, the balun 12 included in the antenna elements 1a to 1f will be described. The balun 12 is a converter for suppressing the generation of an unbalanced current that causes a significant reduction in the efficiency of the antenna when a dipole antenna is connected to the coaxial feeder 11 as in this example. First, the grounded outer peripheral ground wire 11a of the coaxial feeder 11 is set to a zero point, one end of each of the two coils 14 and 15 having the same inductance is connected thereto, and the antenna wire 13 is connected to the other end thereof. A coil 16 having the same inductance as that of the two coils 14 and 15 is connected between the connection point between the one coil 15 and the antenna line 13 and the signal line 11 b of the coaxial feeder 11. A coil circuit connecting the coaxial feeder 11 and the two antenna wires 13 constitutes the balun 12. By providing this balun 12, an unbalanced current is canceled out in each of the outer peripheral ground wire 11a and the signal wire 11b of the coaxial feeder 11 connected to the dipole antenna, and the coaxial feeder 11 itself operates as an antenna. Can be prevented.

FIG. 4 is a functional block diagram showing a detailed configuration of the interrogator 100. As shown in FIG. 4, the signal processing circuit 3 pulses a command bit string generation unit 20 that generates a command bit string corresponding to a transmission signal to the wireless tag T, and a digital signal output from the command bit string generation unit 20 An encoding unit 22 that performs encoding by a predetermined known method such as width modulation, and an AM modulation unit that modulates a signal encoded by the encoding unit 22 using the AM method and supplies (stores) the signal to the transmission memory unit 26 24 and a transmission PAA (Phased Array) that reads the transmission signal stored in the transmission memory unit 26 at any time and multiplies the transmission signal by a predetermined transmission PAA weight.
Antenna) has a transmission weight multiplication unit 28 as a processing unit.

  The high-frequency circuit 2 up-converts a local oscillator 32 that outputs a local oscillation signal having a predetermined frequency and a transmission signal that is output from the transmission weight multiplication unit 28 in accordance with the local oscillation signal that is output from the local oscillator 32. Three high-frequency transmitters 34A, 34B, 34C that transmit the interrogated waves from the three antenna elements 1a to 1c of the transmission array antenna unit 1A after amplification at a predetermined amplification factor, and three of the reception array antenna unit 1B. Three received signals received by the antenna elements 1d to 1f are amplified with a predetermined amplification factor, down-converted according to the local signal output from the local oscillator 32, and supplied (stored) to the reception memory unit 36. It has high frequency receivers 35A, 35B, 35C.

  On the other hand, the signal processing circuit 3 includes the reception memory unit 36 and a reception weight multiplication unit as a reception PAA processing unit that reads the reception signal stored in the reception memory unit 36 as needed and multiplies a predetermined reception PAA weight. 38, an AM demodulator 40 for demodulating the reception signal output from the reception weight multiplier 38 by the AM method to detect an AM demodulated wave, a transmission PAA weight multiplied by a transmission weight multiplier 28, and a reception weight multiplier The reception PAA weight multiplied in the unit 38 and the PAA weight for individually controlling (calculating) the amplification factor for amplifying the transmission signal and the reception signal in the high frequency transmission units 34A, 34B, 34C and the high frequency reception units 35A, 35B, 35C. A control unit (directivity control means) 46 is also provided.

  Further, the signal processing circuit 3 interprets the AM demodulated wave demodulated by the AM demodulating unit 40 by a predetermined known method, and interprets the decoded signal decoded by the decoding unit 42 to transmit the radio signal. A response bit string interpretation unit 44 that reads out an information signal related to the modulation of the tag T is also provided.

  FIG. 5 is a functional block diagram showing detailed functions of the transmission weight multiplying unit 28. As shown in FIG. 5, the transmission weight multiplying unit 28 multiplies the transmission signal read from the transmission memory unit 26 by the transmission PAA weight supplied from the PAA weight control unit 46, respectively. , 34C are provided with a plurality of (three in FIG. 5) multipliers 48a, 48b, 48c. Here, the multiplier 48a corresponds to the high-frequency transmitter 34A, the multiplier 48b corresponds to the high-frequency transmitter 34B, and the multiplier 48c corresponds to the high-frequency transmitter 34C, respectively, and the multipliers 48a, 48b, 48c Is supplied to the corresponding high-frequency transmitters 34A, 34B, 34C.

  FIG. 6 is a functional block diagram showing detailed functions of the high-frequency transmitters 34A, 34B, and 34C. As shown in FIG. 6, the high frequency transmitters 34A, 34B, 34C include a transmission signal D / A converter 50 that converts the transmission signal supplied from the transmission weight multiplier 28 into an analog signal, and the transmission signal D / An up-converter 52 that increases the frequency of the transmission signal analog-converted by the A converter 50 by the frequency of the local oscillation signal output from the local oscillator 32, and the transmission signal up-converted by the up-converter 52 is described later. A transmission signal amplifier 54 that amplifies at a gain set by the weight control unit 46 and supplies the amplified antenna elements 1a to 1c of the transmission array antenna unit 1A.

  FIG. 7 is a functional block diagram showing detailed functions of the high-frequency receiving units 35A, 35B, and 35C. As shown in FIG. 7, the high-frequency receiving units 35A, 35B, and 35C amplify the reception signals supplied from the receiving antenna elements 1d to 1f of the receiving array antenna unit by the PAA weight control unit 46, as described above. A reception signal amplifier 59 that amplifies at a rate, a down converter 61 that lowers the frequency of the reception signal output from the reception signal amplifier 59 by the frequency of the local oscillation signal output from the local oscillator 32, and the down converter 61 A received signal A / D converter 63 that converts the converted received signal into a digital signal and supplies the digital signal to the received memory unit 36 is provided.

  FIG. 8 is a functional block diagram showing detailed functions of the reception weight multiplying unit 38. As shown in FIG. 8, the reception weight multiplying unit 38 multiplies each reception signal read from the reception memory unit 36 by a predetermined reception PAA weight supplied from the PAA weight control unit 46 (three in FIG. 8). ) And a synthesizer 66 that synthesizes the signals output from the multipliers 64a to 64c and supplies them to the AM demodulator 40. Here, the multiplier 64a corresponds to the high frequency receiver 35A, the multiplier 64b corresponds to the high frequency receiver 35B, and the multiplier 64c corresponds to the high frequency receiver 35C.

  In the interrogator 100 having the above-described configuration, the transmission PAA weight set by the central control unit 6 is output to the PAA weight control unit 46 while being sequentially changed, so that the maximum directivity direction during transmission / reception (hereinafter referred to as the main lobe direction). Are sequentially changed to corresponding angles, and the main lobe directions by the three transmitting antenna elements 1a, 1b, and 1c are held so that only one direction corresponding to the transmission PAA weight is strengthened, and the directions are sequentially changed. The so-called phased array control can be performed.

  FIG. 9 is a block diagram illustrating an example of a functional configuration of the RFID circuit element To provided in the RFID tag T.

  In FIG. 9, the RFID circuit element To includes the antenna (tag antenna) 151 that performs non-contact signal transmission / reception with the antenna elements 1a to 1f on the interrogator 100 side using a high frequency such as a UHF band, The IC circuit unit 150 is connected to the antenna 151.

  The IC circuit unit 150 includes a rectifying unit 152 that rectifies the carrier wave received by the antenna 151, a power source unit 153 that accumulates energy of the carrier wave rectified by the rectifying unit 152 and serves as a driving power source, and the antenna 151. A clock extraction unit 154 that extracts a clock signal from the received carrier wave and supplies the clock signal to the control unit 157, and an information storage unit that can store a predetermined information signal such as identification information (hereinafter referred to as a tag ID) of the wireless tag T The RFID circuit element To through the functioning memory unit 155, the modulation / demodulation unit 156 that is connected to the antenna 151 and modulates and demodulates the signal, the rectification unit 152, the clock extraction unit 154, the modulation / demodulation unit 156, etc. The control part 157 for controlling the operation | movement of is provided.

  The modem unit 156 demodulates the communication signals received from the antenna 151 from the antenna elements 1a to 1c of the interrogator 100, and is transmitted from the antennas 1a to 1c based on the return signal from the control unit 157. Reflectively modulate the carrier wave.

  The control unit 157 communicates with the interrogator 100 to store the predetermined information in the memory unit 155, and transmits the interrogation wave received by the antenna 151 to the memory unit 155 in the modulation / demodulation unit 156. After performing modulation based on the stored information signal, basic control such as control of reflecting back from the antenna 151 as a response wave is executed.

  The clock extraction unit 154 extracts a clock component from the received signal and extracts the clock to the control unit 157, and supplies a clock corresponding to the speed of the clock component of the received signal to the control unit 157.

  As described above, the greatest feature of the present embodiment is that the gains of the transmitting antenna elements 1a to 1c and the receiving antenna elements 1d to 1f are minimized in the directions of the transmitting antenna elements 1a to 1c and the receiving antenna elements 1a to 1f. The antenna elements 1d to 1f for use are arranged in so-called null regions where the intensity of the signal from each direction decreases. Hereinafter, the control procedure of the interrogator of this embodiment will be described.

  FIG. 10 is a flowchart showing a control procedure executed by the central control unit 6 of the interrogator 100 having the above configuration. In the example of this flowchart, a control procedure for searching for the presence direction of the wireless tag T corresponding to one designated tag ID as a search target is shown.

  In FIG. 10, this flow is started when a designation of a tag ID and a start of searching for a corresponding wireless tag T are instructed by an operating means (not shown) or an upper control means such as a PC.

  First, in step S5, the response flag F indicating whether or not the search target wireless tag T exists (whether or not there is a response) is reset to 0, and the process proceeds to the next step S10.

  In step S <b> 10, a command such as “Scroll ID” (a command for obtaining a response of the designated tag) including the designated tag ID is output to the command bit string generation unit 20 of the signal processing circuit 3. Thereby, in the signal processing circuit 3, a command bit string corresponding to the input command is generated and encoded by the encoding unit 22, and the encoded information is AM-modulated and transmitted by the AM modulation unit 24 of the signal processing circuit 3. It is stored in the memory unit 26.

  Next, the process proceeds to step S15, where the transmission PAA weight is set to the initial value at the start of transmission. In this example, the main lobe direction θ in the phased array control at the time of transmission is set to the first θo value, and the corresponding transmission PAA weight is calculated and set.

  Next, the process proceeds to step S20, and the transmission PAA weight is output to the transmission weight multiplication unit 28 of the signal processing circuit 3 via the PAA weight control unit 46. Thus, the transmission weight multiplying unit 28 controls the phase of each transmission signal so that the main lobe direction is the θ direction, and each high frequency transmission unit 34A, 34B, 34C converts the transmission signal stored in the transmission memory 26 to a predetermined value. Amplification is performed at the amplification factor, and transmission signals (interrogation waves) actually transmitted from the antenna elements 1a to 1c of the transmission array antenna unit are combined and transmitted mainly in the main lobe direction θ.

  Here, when the search target RFID tag T receives the transmitted transmission signal, a reply signal (response signal) is transmitted in response to the transmission signal, and the reply signal is transmitted from the three antenna elements 1d to 1d of the receiving array antenna unit. Each is received at 1f. At this time, the reply signals received from the antenna elements 1 d to 1 f are amplified with a predetermined amplification factor and stored in the reception memory 36.

  Then, by the search calculation process in the next step S100, the presence direction of the wireless tag T is searched by the calculation of phased array control based on the three reply signals stored in the reception memory 36.

  Next, the process proceeds to step S30, where the transmission PAA weight is updated so that Δθ, which is the step angle in this example, is added to the main lobe direction θ, and the process proceeds to step S35.

  In step S35, it is determined whether or not the main lobe direction θ exceeds θend, which is the last value to be taken in this example, that is, whether or not the search has been completed for all main lobe directions θ to be searched. . This determination may be made based on whether or not the transmission PAA weight exceeds a value corresponding to the main lobe direction θ = θend. If the main lobe direction θ does not exceed θend, the determination is not satisfied, that is, it is necessary to search for the wireless tag T also in the main lobe direction θ at that time, and the process returns to step S20 and the same procedure is repeated. On the other hand, when the main lobe direction θ exceeds θend, the determination is satisfied, that is, the search is finished, and the process proceeds to the next step S40.

  In step S40, it is determined whether or not the response flag F is 1, that is, whether or not the presence of the reply signal from the search target RFID tag T has been confirmed (step S120 in FIG. 11 described later). reference). When the response flag F is 1, the determination is satisfied, that is, the search target wireless tag T is present, the process proceeds to the next step S45, and the maximum received signal strength of the reply signal recorded in the database 5 The main lobe direction θ corresponding to the intensity (see step S125 in FIG. 11 described later) is displayed on the display unit 4 as the direction in which the wireless tag T exists, and this flow is finished. On the other hand, if the response flag F is not 1 (= 0), the determination is not satisfied, that is, the search target wireless tag T is not present in the search target range, the process proceeds to step S50, and the display unit 4 Display that the wireless tag T does not exist, and this flow is finished.

  FIG. 11 is a flowchart showing the detailed procedure of the search calculation process in step S100 in FIG.

  In FIG. 11, first, in step S110, the transmission main lobe direction θ is set as it is as the reception main lobe direction θ as it is, and the corresponding reception PAA weight is set, and the signal processing circuit is set via the PAA weight control unit 46. 3 is output to the reception weight multiplication unit 38. As a result, the reception weight multiplication unit 38 controls the phase of each of the three reply signals stored in the reception memory 36, and can be synthesized as a reception signal when the main lobe direction θ is received as the directivity direction. . The received signal is AM demodulated by the AM demodulating unit 40, the demodulated information is decoded by the decoding unit 42 of the signal processing circuit 3, and becomes a reply signal that can be discriminated by the central control unit 6 by the reply bit string interpreting unit 44. And input to the central control unit 6.

  Next, the process proceeds to step S115, and it is determined by a known error detection method (for example, using a CRC code) whether or not the input reply signal is in a normal state as a reply signal from the search target wireless tag T. To do. If the input reply signal is normal, the determination is satisfied, that is, it is considered that the search target RFID tag T has been detected, and the process proceeds to the next step S120.

  In step S120, the response flag F is updated to 1 to indicate that the search target RFID tag T has been confirmed. In the next step S125, the response is obtained from the current main lobe direction θ and the AM demodulator 40. The received signal strength of the reply signal is stored in the database 5 (in FIG. 4, signal lines for inputting the received signal strength from the AM demodulator 40 to the central controller 6 are not shown). Then, this flow ends.

  On the other hand, if the input reply signal is not normal in the determination in step S115, it is determined that the determination is not satisfied, that is, the search target wireless tag T has not been detected, and this flow is ended as it is.

  In the present embodiment configured as described above, a transmission signal including a carrier wave is transmitted to the RFID circuit element To from each of the antenna elements 1a to 1c of the transmission array antenna unit 1A, and the RFID circuit element To is contactless. The IC circuit unit 150 is accessed. A response signal returned in response to the signal is received in a non-contact manner by each of the antenna elements 1d to 1f of the reception array antenna unit 1B, and information is transmitted to and received from the RFID circuit element To. At this time, since the amount of attenuation (transmission / reception separation) between the antenna elements 1a to 1c on the transmission side and the antenna elements 1d to 1f on the reception side is finite, the transmission wave is each antenna element on the reception side. If the signals are received and mixed at 1d to 1f, they may become interference signals and interfere with reception of the response signal from the RFID circuit element To.

  In the interrogator 100 of the present embodiment, the antenna elements 1a to 1c of the transmission array antenna unit 1A and the antenna elements 1d to 1f of the reception array antenna unit 1B are in directions in which gains are substantially minimized (so-called null directions). Is arranged. As a result, when viewed from the antenna elements 1a to 1c on the transmission side, the transmitted wave hardly reaches the antenna elements 1d to 1f on the reception side, and viewed from the antenna elements 1a to 1c on the reception side. And the antenna elements 1a to 1c on the transmission side are arranged in a direction where there is almost no gain at the time of reception (signals from the respective directions of the antenna elements 1a to 1c on the transmission side and the antenna elements 1d to 1f on the reception side) The strength of the is reduced). As a result, reception interference due to mixing of transmission waves from the antenna elements 1a to 1c on the transmission side to the antenna elements 1d to 1f on the reception side can be reduced, and information transmission / reception accuracy can be improved.

  Further, in this embodiment, in particular, a transmission array antenna unit 1A and a reception array antenna unit 1B configured by array antennas are used, and a dipole antenna is used as the transmission antenna elements 1a to 1c and the reception antenna elements 1d to 1f, respectively. The dipole antennas are arranged so that the axis lines of the elements are substantially aligned with each other (arranged like the antenna element 1b on the transmission side and the antenna element 1e on the reception side in FIG. 2). Thereby, it is possible to reliably arrange the gains to be substantially minimum, thereby preventing reception interference due to mixing of transmission waves from the antenna elements 1a to 1c on the transmission side to the antenna elements 1d to 1f on the reception side. Can be reduced.

  Further, based on the fact that the resolution can be improved as the interval between the antenna elements is increased, in this embodiment, in particular, the arrangement interval δ1 between the plurality of antenna elements 1a to 1c of the transmission array antenna unit 1A and the reception array antenna unit The arrangement interval δ2 between the plurality of 1B antenna elements 1d to 1f is made different, so that δ2> δ1. As a result, the resolution on the reception side can be made larger than the resolution on the transmission side, so that the directivity direction in which the response wave is received is clarified and the location of the RFID tag T is searched reliably and with high accuracy. Can do.

  In the first embodiment, all the antenna elements are arranged side by side on the same plane regardless of the transmitting side and the receiving side. However, the present invention is not limited to this, and each antenna element is arranged along a curved surface. You may comprise so that it may provide.

  The configuration of this modification is different from the configuration of the above embodiment only in the configuration of the antenna unit, and only the configuration that is different will be described below. .

  FIG. 12 is a diagram illustrating a detailed configuration of the antenna unit 201 in the interrogator 200 in the case of this modification. The antenna unit 201 includes a transmission array antenna unit 201A and a reception array antenna unit 201B, and is arranged in a direction in which the gain is the smallest.

  In FIG. 12, a transmission array antenna unit 201A has three transmission antenna elements 1a to 1c. The reception array antenna unit 201B includes three reception antenna elements 1d to 1f. The three transmitting antenna elements 1a to 1c are arranged along the curved surface Fc with the maximum communication distance L of each antenna element 1a to 1c as a common radius of curvature, and are provided in the transmitting array antenna unit 201A so as to be parallel to each other. It has been.

  The antenna elements 1d to 1f of the reception array antenna unit 201B are located on the same straight line as the antenna elements 1a to 1c of the transmission array antenna unit 201A, that is, are arranged in parallel with each other along the same curved surface Fc. A receiving array antenna unit 201B is provided.

  The three transmitting antenna elements 1a to 1c shown in the figure constitute the transmitting array antenna unit 201A in the present modification, and the three receiving antenna elements 1d to 1f serve as the receiving array antenna unit 201B in the present modification. It is composed.

  In this modified example configured as described above, the same effects as those of the first embodiment can be obtained, and in addition, the following effects can be obtained.

  That is, for example, when a plurality of antenna elements are arranged on a substantially flat surface (not shown in particular), the transmission performance and reception with respect to the same RFID tag T are increased as the antenna elements are located at both ends from the antenna element located at the center side. Sensitivity will decrease.

  Therefore, in the present modification, the antenna elements 1a to 1f are arranged along the curved surface Fc, the radius of curvature is made common, and the distances between the antenna elements 1a and the wireless tag T are made substantially the same, thereby avoiding the above-described adverse effects. Any antenna element 1a to 1f can have substantially the same communication conditions.

  In this modification, in particular, the curvature radius L of the curved surface Fc is set so as to correspond to the maximum communication distance of each of the antenna elements 1a to 1f, so that reliable communication is ensured for any of the antenna elements 1a to 1f. Can be secured.

  Next, a second embodiment of the present invention will be described with reference to the drawings. The present embodiment is an example in which each antenna element is configured by a planar antenna. The configuration of the present embodiment is different from the configuration of the first embodiment only in the configuration of the antenna unit (the number of high-frequency transmitters 34 and high-frequency receivers 35 is also appropriately set). Only the configuration will be described, and the same components will be denoted by the same reference numerals, and description thereof will be omitted as appropriate (the same applies to the following modifications).

  FIG. 13 is a diagram illustrating a detailed configuration of the antenna unit in the interrogator in the present embodiment, and corresponds to FIG. 2 described above. FIG. 14 is a cross-sectional view taken along the XIV-XIV ′ section in FIG.

  In FIG. 13, the antenna unit 301 includes two transmitting antennas 301a and 301b and two receiving antennas 301d and 301e. Each of the antennas 301a, 301b, 301d, and 301e (hereinafter referred to as the antennas 301a to 301e for convenience) is a planar antenna (microstrip antenna) that has the same size and is formed in a substantially rectangular flat plate shape. The two antennas 301a and 301b for transmission and the two antennas 301d and 301e for reception are alternately arranged in a staggered arrangement in parallel with the antenna unit 301.

  Further, in FIG. 14, a pair of adjacent antennas 301a and 301d (for transmission and reception) are arranged close to each other, so that part of each signal radiation pattern R1 and R2 is shown in the figure. Duplicate. The interrogator 200 according to the present embodiment can transmit and receive signals to and from the wireless tag T inside the overlapping portion of the signal radiation patterns R1 and R2. With respect to the signal radiation pattern R1 from the transmission-side antenna 301a, the reception-side antenna 301d is substantially in the null direction N of the transmission-side antenna 301a. Conversely, the positional relationship between the signal radiation pattern R2 from the receiving-side antenna 301d and the transmitting-side antenna 301a is the same. Furthermore, the antennas on the transmitting side and the receiving side that are adjacent in other combinations have the same arrangement relationship.

  FIG. 15A is a side view showing the detailed structure of the planar antenna, and FIG. 15B is a cross-sectional view thereof. 15A and 15B, the planar antennas 301a to 301d include a microstrip antenna element 51 on one side (upper side in the figure) and a ground plane 52 on the other side (lower side in the figure). A dielectric 53 is provided in the middle so as to be sandwiched between them. A through hole 54 is provided at one location of the ground plane 52 and the dielectric 53. A microstrip line 55 serving as a feed line to the planar antennas 301 a to 301 d, one end of which is connected to the high frequency transmitter 34 or the high frequency receiver 35 (see FIG. 4 above), is connected to the microstrip antenna element via the through hole 54. 51 is extended and connected to a feeding point P provided at 51.

  In addition, also about the control procedure which the central control part 6 implements, according to the same flowchart as the said embodiment, the same control can be performed.

  Also in the second embodiment configured as described above, it is possible to search for the wireless tag T by phased array control in transmission and reception as in the first embodiment. In addition, the planar antennas 301a to 301e are used as the transmitting antenna and the receiving antenna, and the planar antennas 301a to 301e are disposed so as to be on the same plane, so that the gain is substantially minimized. Accordingly, similarly to the first embodiment, it is possible to reduce reception interference by reducing the mixing of transmission waves from the antennas 301a and 301b on the transmission side to the antennas 301d and 301e on the reception side.

  In this embodiment, in particular, the plurality of planar antennas 301a and 301b on the transmission side and the plurality of planar antennas 301d and 301e on the reception side are arranged in a staggered pattern on the same plane. (The existence range of the RFID circuit element To that the transmission signal can reach, see the signal radiation pattern R1 in FIG. 14 described above) and the communicable range seen on the receiving side (the existence of the RFID circuit element To that can receive the response signal) The overlapping portion with the range and the signal radiation pattern R2 in FIG. 14 described above can be made wider. As a result, the communication range seen with the interrogator 200 as a whole can be further increased.

  This is because, for example, the above-described overlapping portion that enables transmission / reception of signals to / from the wireless tag T than when the antennas on the transmitting side are adjacent to each other, the antennas on the receiving side are adjacent to each other, and the antenna pairs are adjacent to each other is provided. Means that it can be formed widely.

  In the second embodiment, as in the modification of the first embodiment, all the planar antennas may be arranged along the curved surface regardless of the transmitting side and the receiving side. . That is, as shown in FIG. 16, the transmission-side antennas 401a and 401b and the reception-side antenna 401d that are alternately arranged have the same center of curvature as the center of the same wireless tag, and each antenna 401a, 401b, and 401d. May be provided in the antenna unit 401 in an arrangement along the curved surface Fc with the maximum communication distance as a common radius of curvature. In addition, the transmitting antenna 401c and the receiving antennas 401e and 401f are alternately arranged in a staggered arrangement so as to overlap with the inner sides of the transmitting antennas 401a and 401b and the receiving antenna 401d as viewed from the paper. Yes. Even if comprised in this way, the effect similar to the modification of the said 1st Embodiment is acquired.

  It is assumed that the “Scroll ID” signal and the like used above comply with the specifications formulated by EPC global. EPC global is a non-profit corporation established jointly by the International EAN Association, which is an international organization of distribution codes, and the United Code Code Council (UCC), which is an American distribution code organization. Note that signals conforming to other standards may be used as long as they perform the same function.

  In addition to those already described above, the methods according to the above-described embodiments and modifications may be used in appropriate combination.

  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 system configuration figure showing the whole outline of the RFID tag communications system which is the application object of a 1st embodiment. It is a functional block diagram showing the detailed structure of an antenna unit among the interrogators shown in FIG. It is a figure showing the detailed structure of the antenna element shown in FIG. It is a functional block diagram showing the detailed structure of an interrogator. It is a functional block diagram showing the detailed function of a transmission weight multiplication part. It is a functional block diagram showing the detailed function of a high frequency transmission part. It is a functional block diagram showing the detailed function of a high frequency receiving part. It is a functional block diagram showing the detailed function of a reception weight multiplication part. It is a block diagram showing an example of a functional structure of the radio | wireless tag circuit element with which the radio | wireless tag was equipped. It is a flowchart showing the control procedure performed by the central control part of an interrogator. It is a flowchart showing the detailed procedure of the search calculation process of step S100 in FIG. It is a figure showing the detailed structure of an antenna unit among the interrogators in the case of the modification which provides each antenna element by arrangement | positioning along a curved surface. It is a figure showing the detailed structure of an antenna unit among the interrogators in the case of 2nd Embodiment. It is a cross-sectional view by the XIV-XIV 'cross section in FIG. It is the side view and sectional drawing showing the detailed structure of a planar antenna. It is a figure showing the detailed structure of an antenna unit among the interrogators in the case of the modification provided with each antenna element by arrangement | positioning along a curved surface in 2nd Embodiment.

Explanation of symbols

1 Antenna unit 1A Transmitting array antenna section (array antenna)
1B receiving array antenna (array antenna)
1a Antenna element (transmitting antenna, dipole antenna)
1b Antenna element (transmitting antenna, dipole antenna)
1c Antenna element (transmitting antenna, dipole antenna)
1d Antenna element (receiving antenna, dipole antenna)
1e Antenna element (receiving antenna, dipole antenna)
1f Antenna element (receiving antenna, dipole antenna)
2 High Frequency Circuit 3 Signal Processing Circuit 4 Display Unit 5 Database 6 Central Control Unit 100 Interrogator 300 Interrogator 301 Antenna Unit 301a Antenna (Transmission Antenna, Planar Antenna)
301b Antenna (transmitting antenna, planar antenna)
301d Antenna (receiving antenna, planar antenna)
301e Antenna (receiving antenna, flat antenna)
T wireless tag To wireless tag circuit element

Claims (10)

A signal including at least a carrier wave is transmitted in a non-contact manner to an RFID circuit element having a tag-side antenna connected to the IC circuit unit for storing predetermined information and the IC circuit unit, and the IC circuit unit is accessed. A transmit antenna to perform,
A receiving antenna that is provided separately from the transmitting antenna and receives a response signal returned from the IC circuit unit in response to the signal transmitted by the transmitting antenna;
An interrogator for an RFID tag communication system, wherein the transmission antenna and the reception antenna are arranged so as to be positioned in a direction in which a gain is substantially minimized. The interrogator of the RFID tag communication system according to claim 1,
The interrogator of the RFID tag communication system, wherein the transmitting antenna and the receiving antenna are dipole antennas extending substantially in a straight line. The interrogator of the RFID tag communication system according to claim 1,
The interrogator of the RFID tag communication system, wherein the transmitting antenna and the receiving antenna are array antennas composed of a plurality of antenna elements. The interrogator of the RFID tag communication system according to claim 3,
An interrogator for an RFID tag communication system, wherein an arrangement interval between the plurality of antenna elements of the transmission antenna is different from an arrangement interval between the plurality of antenna elements of the reception antenna. The interrogator of the RFID tag communication system according to claim 4,
An interrogator for an RFID tag communication system, wherein an arrangement interval between the plurality of antenna elements of the receiving antenna is larger than an arrangement interval between the plurality of antenna elements of the transmission antenna. The interrogator of the RFID tag communication system according to any one of claims 3 to 5,
The interrogator of the RFID tag communication system, wherein each of the plurality of antenna elements is arranged along a curved surface having a predetermined curvature in the transmission antenna or the reception antenna. The interrogator of the RFID tag communication system according to claim 1,
The interrogator of the RFID tag communication system, wherein the transmitting antenna and the receiving antenna are planar antennas. The interrogator of the RFID tag communication system according to claim 7,
The plurality of transmitting antennas and the plurality of receiving antennas are arranged on substantially the same plane,
An interrogator for an RFID tag communication system, wherein transmission antennas and reception antennas are alternately arranged in a staggered pattern on the plane. The interrogator of the RFID tag communication system according to claim 7,
An interrogator for an RFID tag communication system, wherein a plurality of transmitting antennas or a plurality of receiving antennas are arranged along a curved surface having a predetermined curvature. The interrogator of the RFID tag communication system according to claim 6 or 8,
An interrogator for an RFID tag communication system, wherein a curvature radius of the curved surface is set according to a maximum communication distance.

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