JP2008045953A - Direction detection device - Google Patents

Abstract

A direction detection apparatus that realizes suitable direction detection by reducing the influence of multipath is provided.
An array antenna 16 composed of a plurality of antenna elements 26, and a directivity control unit that controls the transmission and / or reception directivity of the array antenna 16 by controlling the phase corresponding to each of the antenna elements 26. 54, a reception signal received by the directivity control unit 54 when the transmission and / or reception directivity of the array antenna 16 is set to the directivity direction corresponding to the first angle, and a predetermined value based on the first angle. A direction detection unit 60 that detects the direction of the wireless tag 14 by comparing the received signal received when the directivity direction corresponding to the second angle shifted is used. Therefore, the direction of the wireless tag 14 can be suitably detected by using a reception result corresponding to an angle with less influence of multipath.
[Selection] Figure 2

Description

  The present invention relates to a direction detection device that transmits and / or receives a radio signal to a radio terminal and detects the direction of the radio terminal based on the radio signal, and particularly reduces the influence of multipath. It relates to technology.

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

  As one form of such a wireless tag communication device, use as a direction detection device that detects the direction of the wireless tag based on a response wave from the wireless tag has been proposed. For example, this is the wireless tag position detection system described in Patent Document 1. According to this technology, an interrogation wave is transmitted toward a radio tag to be detected, a response wave returned from the radio tag according to the interrogation wave is received, and a radio wave is transmitted between the radio tag and the radio tag. It is said that the direction or position of the wireless tag can be detected by performing communication.

JP 2006-105723 A

  However, when the direction of a wireless terminal is detected by PAA (Phased Array Antenna) processing in the conventional technology as described above, a plurality of radio wave reception paths are generated due to reflection or diffraction caused by an obstacle. Due to the influence, it becomes difficult to detect the direction of the wireless terminal because the wireless signal from the direction corresponding to the wireless terminal to be detected becomes weak or the wireless signal from the direction in which no wireless terminal exists becomes strong. There was a risk of becoming. For this reason, development of the direction detection apparatus which implement | achieves suitable direction detection by reducing the influence of multipath was calculated | required.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a direction detection device that reduces the influence of multipath and realizes suitable direction detection.

  In order to achieve such an object, the gist of the present invention is to perform direction detection in which a radio signal is transmitted to and / or received from a radio terminal and the direction of the radio terminal is detected based on the radio signal. An array antenna comprising a plurality of antenna elements for transmitting a radio signal to the radio terminal and / or receiving a radio signal from the radio terminal, and each of the plurality of antenna elements A directivity control unit that controls the transmission directivity and / or reception directivity of the array antenna by controlling the phase corresponding to the transmission antenna, and the transmission directivity and / or reception directivity of the array antenna by the directivity control unit Corresponding to a received signal received in the case of a directivity direction corresponding to the first angle and a second angle shifted by a predetermined deviation angle from the first angle. And a reception signal received in case of a tropism direction, and a direction detector for detecting a direction of the wireless terminal by comparison, is characterized in that it comprises.

  If it does in this way, an array antenna constituted by a plurality of antenna elements for transmitting a radio signal to the radio terminal and / or receiving a radio signal from the radio terminal, and the plurality of antenna elements A directivity control unit that controls the transmission directivity and / or reception directivity of the array antenna by controlling the phase corresponding to each, and the transmission directivity and / or reception directivity of the array antenna by the directivity control unit Received in the case of the directivity direction corresponding to the first angle and received in the case of the directivity direction corresponding to the second angle shifted by a predetermined deviation angle from the first angle. A direction detection unit that detects the direction of the wireless terminal by comparing the received signal with the received signal. By using the reception result in the directivity direction corresponding to the angle is less affected paths, it is possible to suitably detect the direction of the wireless terminal. That is, it is possible to provide a direction detection device that reduces the influence of multipath and realizes suitable direction detection.

  Here, preferably, a signal strength detection unit that detects a signal strength of a reception signal received by the array antenna is provided, and the direction detection unit is configured to perform the signal detection according to the signal strength detected by the signal strength detection unit. The direction of the wireless terminal is detected. In this way, the direction of the wireless terminal can be detected in a practical manner.

  Preferably, the direction detection unit receives a received signal or a signal thereof when the first angle is changed stepwise by a predetermined angle and the directivity direction corresponds to the first angle. The received signal received when the intensity and the directivity direction corresponding to the second angle or the signal intensity are stored in a predetermined storage device, and the received signal or the signal stored in the storage device The direction of the wireless terminal is detected by comparing the intensities. In this way, it is possible to determine the directivity direction corresponding to the angle with less influence of the multipath in a practical manner, and it is possible to suitably detect the direction of the wireless terminal.

  Preferably, the deviation angle is not less than 1/10 and not more than 1/5 of a predetermined angle that is a stepwise change in the first angle. In general, even if the directivity direction of the array antenna is shifted by a sufficiently small angle, the received signal strength due to the direct wave is hardly changed, but the influence of multipath changes greatly because the path difference between the direct wave and the indirect wave changes. . Therefore, by comparing the received signal corresponding to each directivity direction by shifting the directivity direction of the array antenna by a deviation angle sufficiently smaller than the predetermined angle, the directivity corresponding to the angle with less influence of multipath is obtained. The direction of the wireless terminal can be determined, and the direction of the wireless terminal can be suitably detected.

  Preferably, the deviation angle is in the range of 1 to 2 °. In general, even if the directivity direction of the array antenna is shifted within a range of 1 to 2 °, the received signal intensity due to the direct wave is hardly changed, but the influence of multipath is affected by the change in the path difference between the direct wave and the indirect wave. It changes a lot. Therefore, the directivity direction corresponding to the angle with less influence of multipath is determined by comparing the received signals corresponding to the directivity directions by shifting the directivity direction of the array antenna within a range of 1 to 2 °. And the direction of the wireless terminal can be suitably detected.

  Preferably, the deviation angle is equal to or smaller than an allowable error angle in the direction detection of the wireless terminal. In this way, by shifting the directivity direction of the array antenna within a range equal to or less than the allowable error angle in direction detection and comparing the received signals corresponding to the directivity directions, the angle with less influence of multipath is obtained. The corresponding directivity direction can be determined, and the direction of the wireless terminal can be suitably detected.

  Preferably, the direction detection unit first changes the transmission directivity and / or reception directivity of the array antenna by the directivity control unit while gradually changing the first angle by a predetermined angle. The received signal received in the case of the directivity direction corresponding to the first angle or the signal strength thereof is stored in the storage device, and then the first angle is changed step by step by a predetermined angle. Received when the directivity control unit sets the transmission directivity and / or reception directivity of the array antenna to a directivity direction corresponding to a second angle shifted from the first angle by a predetermined deviation angle. The received signal or the signal strength thereof is stored in the storage device, and the direction of the wireless terminal is detected by comparing the received signal or the signal strength stored in the storage device. In this way, it is possible to determine the directivity direction corresponding to the angle with less influence of the multipath in a practical manner, and it is possible to suitably detect the direction of the wireless terminal.

  Preferably, when the signal strength of the received signal received when the direction detection unit has a directivity direction corresponding to the first angle is equal to or less than a predetermined value, the first angle The directivity control corresponding to the second angle shifted by a predetermined deviation angle and the transmission and / or reception control of the radio signal are not performed. In this way, the time required for detecting the direction of the wireless terminal can be shortened by omitting the control corresponding to the second angle in the direction in which suitable communication cannot be performed due to the presence of an obstacle. Can do.

  Preferably, the direction detection unit compares the detection results detected by the signal intensity detection unit for each reception signal stored in the storage device, and the transmission direction in which the detection result takes a maximum value. And / or a direction corresponding to the reception directivity is detected as the direction of the wireless terminal. In this way, the direction of the wireless terminal can be detected in a practical manner.

  Preferably, the direction detection unit compares detection results detected by the signal intensity detection unit for each received signal stored in the storage device, and the detection result corresponds to the first angle. The direction corresponding to the transmission directivity and / or the reception directivity that is equal to or greater than a predetermined threshold in both the directivity direction and the directivity direction corresponding to the second angle is detected as the direction of the wireless terminal. In this way, the direction of the wireless terminal can be detected in a practical manner.

  Preferably, the direction detection unit compares a detection result detected by the signal intensity detection unit for each reception signal stored in the storage device, and determines a directivity direction corresponding to the first angle. The direction corresponding to the angle with the smallest difference between the detection result and the detection result of the directivity direction corresponding to the second angle is detected as the direction of the wireless terminal. In this way, the direction of the wireless terminal can be detected in a practical manner.

  Preferably, the direction detection unit includes the signal intensity for each of the received signals stored in the storage device with respect to the directivity direction corresponding to the first angle and the directivity direction corresponding to the second angle. The detection results detected by the detection unit are averaged, and the direction corresponding to the transmission directivity and / or reception directivity at which the detection result takes the maximum value in the directivity direction corresponding to the average large angle is determined by the wireless terminal. The direction is detected. In this way, the direction of the wireless terminal can be detected in a practical manner.

  Preferably, the obstacle direction detection unit for detecting the direction in which the obstacle exists by comparing each received signal or signal intensity stored in the storage device, or the direction of the obstacle is known. An obstacle direction setting unit for setting the direction of the obstacle is provided, and the direction detection unit excludes the direction in which the obstacle is detected by the obstacle direction detection unit or the direction set in the obstacle direction setting unit. Thus, the direction of the wireless terminal is detected. In this way, the direction of the wireless terminal can be suitably detected by avoiding the direction in which the obstacle causing the multipath occurs.

  Preferably, the direction detecting device transmits a predetermined transmission signal toward the detection target wireless tag and receives a return signal returned from the wireless tag in response to the transmission signal. The wireless tag direction detecting device detects the direction of the wireless tag. In this way, it is possible to provide a wireless tag direction detection device that reduces the influence of multipath and realizes detection of a preferable wireless tag direction.

  Preferably, the direction detection unit detects a direction of the wireless tag by changing a frequency of a carrier wave of the transmission signal and comparing a reception signal received corresponding to each frequency. . In this way, by comparing the received signals received corresponding to the respective directivity directions in each of the plurality of carrier frequencies, and using the reception result with the carrier frequency with less multipath effect, the direction of the wireless tag Can be detected more suitably.

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

FIG. 1 is a diagram for explaining an RFID tag communication system 10 in which the direction detection device of the present invention is preferably used. The RFID tag communication system 10 includes an RFID tag communication device 12 which is an embodiment of the direction detection device of the present invention, and a single or plural (in FIG. 1, singular) radio terminals to be detected by the RFID tag communication device 12. ) Of the RFID tag 14, the RFID tag communication device 12 functions as an interrogator of the RFID system, and the RFID tag 14 functions as a responder. That is, when the interrogation wave F _c (transmission signal) is transmitted from the radio tag communication device 12 toward the radio tag 14, a predetermined command (transmission data) is received in the radio tag 14 that has received the interrogation wave F _c. As a result, the interrogation wave F _c is modulated and sent back to the RFID tag communication apparatus 12 as a response wave F _r (reply signal), so that information is transmitted between the RFID tag communication apparatus 12 and the RFID tag 14. Communication takes place. By such communication, the direction or position of the wireless tag 14 relative to the wireless tag communication device 12 is detected. The wireless tag communication system 10 is used, for example, for managing articles in a predetermined communication area. The wireless tag 14 is preferably attached to an article to be managed, for example. And are provided integrally.

  FIG. 2 is a diagram illustrating the configuration of the wireless tag communication device 12. As shown in FIG. 2, the RFID tag communication apparatus 12 of the present embodiment includes a carrier generation unit 20 that generates a carrier wave of a predetermined frequency in response to a command from a direction detection unit 60 described later, and the carrier generation unit 20 A carrier wave amplification unit 22 for amplifying the carrier wave output from the carrier wave, and a transmission signal based on the carrier wave supplied from the carrier wave amplification unit 22 is transmitted from the corresponding antenna element 26 and the reception signal received by the antenna element 26 is processed. A plurality of (three in FIG. 2) transmission / reception modules 24a, 24b, and 24c (hereinafter simply referred to as transmission / reception modules 24 unless otherwise specified) and the transmission / reception modules 24a, 24b, and 24c are provided. Antenna elements 26a, 26b, 26c for both transmission and reception (hereinafter simply referred to as antenna element 26 unless otherwise distinguished) The reception signal combining unit 28 that is a combining unit that combines (adds) the reception signals supplied from the plurality of transmission / reception modules 24, and the variable amplification unit 30 that amplifies the combined signal supplied from the reception signal combining unit 28. And a homodyne detection circuit 32 for performing homodyne detection on the combined signal supplied from the variable amplification unit 30 and a signal in a predetermined frequency band among the I-phase signals (in-phase components) output from the homodyne detection circuit 32. An I-phase LPF (Low Pass Filter) 34, an I-phase A / D converter 36 for digitally converting the I-phase signal that has passed through the I-phase LPF 34, and a signal digitally converted by the I-phase A / D converter 36 And a signal in a predetermined frequency band among the Q-phase signal (orthogonal component) output from the homodyne detection circuit 32 and the I-phase memory unit 38 for storing the signal. Phase LPF 40, Q phase A / D converter 42 that digitally converts the Q phase signal that has passed through the Q phase LPF 40, and Q phase memory unit that stores the signal digitally converted by the Q phase A / D converter 42 44. In addition, in order to perform direction detection control for detecting the direction of the wireless tag 14, the transmission data generation unit 50, the directivity control unit 54, the signal intensity detection unit 56, the obstacle direction detection unit 58, and the obstacle direction setting unit 59 And a direction detection unit 60.

  The antenna element 26 is, for example, a linear antenna element such as a dipole antenna. Preferably, the plurality of linear antenna elements 26 are arranged in parallel and at equal intervals in the same plane. . In the RFID tag communication apparatus 12 of the present embodiment, the array antenna 16 that is shared for transmission and reception is constituted by the plurality of linear antenna elements 26. Preferably, among the plurality of linear antenna elements 26 constituting the array antenna 16, the distance between the linear antenna elements 26 arranged farthest from each other, that is, between the antenna elements 26a and 26c. Is less than the wavelength of the carrier wave generated by the carrier wave generator 20.

  FIG. 3 is a diagram for explaining the configuration of the transmission / reception module 24 in detail. As shown in FIG. 3, the transmission / reception module 24 includes a transmission phase shifter 62 that is a variable phase shifter for controlling the phase of the carrier wave supplied from the carrier wave amplifier 22, and the transmission phase shifter 62. Provided in a signal transmission path between the transmission amplifier 64 and the antenna element 26, and a transmission amplifier 64 which is a variable gain amplifier for modulating the carrier wave output from the transmitter with predetermined transmission data and outputting the transmission signal. And the transmission signal output from the transmission amplifier 64 is supplied to the antenna element 26 through the filter 68 and received by the antenna element 26 and supplied through the filter 68. A transmission / reception separator 66 for supplying a signal to the reception amplifier 70, and a control for controlling the phase of the reception signal supplied from the transmission / reception separator 66. And a reception phase shifter 70 is a phase shifter, a.

FIG. 4 is a diagram for explaining the configuration of the RFID circuit element 72 provided in the RFID tag 14. As shown in FIG. 4, the RFID circuit element 72 processes an antenna unit 74 for transmitting / receiving signals to / from the RFID tag communication device 12 and a signal received by the antenna unit 74. And an IC circuit unit 76 for the purpose. The IC circuit unit 76 rectifies the interrogation wave F _c received from the RFID tag communication device 12 received by the antenna unit 74, and the energy of the interrogation wave F _c rectified by the rectification unit 78. Functions as a power supply unit 80 for accumulation, a clock extraction unit 82 that extracts a clock signal from the carrier wave received by the antenna unit 74 and supplies the clock signal to the control unit 88, and an information storage unit that can store a predetermined information signal The RFID circuit element 72 via the memory unit 84, the modulation / demodulation unit 86 that is connected to the antenna unit 74 and modulates and demodulates the signal, the rectification unit 78, the clock extraction unit 82, the modulation / demodulation unit 86, and the like. And a control unit 88 for controlling the operation of. The control unit 88 performs control to store the predetermined information in the memory unit 84 by communicating with the wireless tag communication device 12, and transmits the interrogation wave F _c received by the antenna unit 74 to the modulation / demodulation unit 86. in executing the basic control as a response wave F _r of the control or the like that reflects back from the antenna unit 74 in terms of modulated based on the information signal stored in the memory unit 84.

  Returning to FIG. 2, the transmission data generation unit 50 generates transmission data to be transmitted to the wireless tag 14 on the carrier wave generated by the carrier wave generation unit 20 and transmits the transmission amplifier 64 in each transmission / reception module 24. To supply. In the transmission amplifier 64, modulation is performed based on the transmission data supplied from the transmission data generation unit 50 to obtain a transmission signal, which is transmitted from the antenna element 26 through the filter 68 and the like.

  The directivity control unit 54 controls the transmission directivity and / or reception directivity of the array antenna 16 composed of the plurality of antenna elements 26. Specifically, the transmission directivity of the array antenna 16 is controlled by controlling the phase of the transmission signal transmitted from the corresponding antenna element 26 via the transmission phase shifter 62 in each transmission / reception module 24. In addition, the reception directivity of the array antenna 16 is controlled by controlling the phase of the reception signal received by the corresponding antenna element 26 via the reception phase shifter 70 in each transmission / reception module 24.

  The signal strength detector 56 detects the signal strength of the received signal received by the array antenna 16. Specifically, the I-phase signal stored in the I-phase memory unit 38 and the Q-phase signal stored in the Q-phase memory unit 44 are read, and the square root of the sum of the squares of the I-phase signal and the Q-phase signal is calculated. The signal strength of the received signal corresponding to these I-phase signal and Q-phase signal is detected by calculating and the like.

  The obstacle direction detector 58 detects the direction in which the obstacle exists by comparing the received signals received as a result of transmission or reception by the array antenna 16. This detection is preferably performed based on the detection result of the signal intensity detection unit 56. That is, the obstacle direction detection unit 58 detects a direction in which the signal intensity of the received signal received is minimized or maximized as a direction in which the obstacle exists as a result of transmission or reception by the array antenna 16. . The obstacle direction setting unit 59 sets the direction when the obstacle direction is known.

  The direction detection unit 60 receives a received signal when the directivity control unit 54 sets the transmission directivity and / or reception directivity of the array antenna 16 to the directivity direction corresponding to the first angle; The direction of the wireless tag 14 is detected by comparing the received signal with the directivity direction corresponding to the second angle shifted by a predetermined deviation angle (minute angle) from the first angle. To do. Hereinafter, the direction detection control of the wireless tag 14 by the direction detection unit 60 will be described in detail.

  FIG. 5 is a diagram for explaining multipath that occurs when the RFID tag communication system 10 is operated in the room 90. As shown in FIG. 5, when the RFID tag communication system 10 is operated in a room 90 having walls 92 that are obstacles (radio wave reflectors other than the RFID tag 14 to be detected) on all sides, the walls It is conceivable that a so-called multipath is generated separately from the direct wave path due to reflection or diffraction caused by 92. In FIG. 5, the direct wave and multipath are indicated by solid line arrows when the transmission directivity and / or reception directivity of the array antenna 16 is a directivity direction corresponding to a predetermined first angle, and the first angle The direct wave and the multipath in the case of the directivity direction corresponding to the second angle shifted by a predetermined deviation angle from are respectively indicated by broken line arrows. When a multipath occurs in this way, the multipath and the direct wave have different phases depending on the path. Therefore, the signal of the direct wave path is strengthened or weakened by the signal of the multipath path. Also, radio waves can reach places where direct waves do not reach due to multipath.

  FIG. 6 shows the signal strength of the received signal and the respective first angles when the first angle is changed step by step by a predetermined angle and the directivity direction corresponding to the first angle is set. It is a figure which compares and shows the signal strength of the received signal received when it is set as the directivity direction corresponding to the 2nd angle shifted by a predetermined deviation angle, and shows the received signal strength corresponding to the first angle. The solid line indicates the received signal intensity corresponding to the second angle by a broken line. FIG. 6 shows that the first angle is −40 ° with respect to a predetermined reference direction, for example, a direction indicated by a straight line passing through the antenna element 26b disposed in the center and perpendicular to the plane in which the antenna element 26 is disposed. In this case, the direction detecting unit 60 preferably corresponds to a predetermined relative angle range determined in advance in a stepwise manner from 10 ° to 40 °. The control unit 54 performs control to change the transmission directivity and / or reception directivity of the array antenna 16 step by step by a predetermined angle, and the received signal is received corresponding to each transmission directivity and / or reception directivity. Are detected, the direction of the wireless tag 14 is detected. Further, the deviation angle, that is, the deviation of the second angle from the first angle is preferably 1/10 or more and 1/5 or less of a predetermined angle that is a stepwise change of the first angle. Yes, in the example shown in FIG. In general, even if the directivity direction of the array antenna is shifted within a range of 1 to 2 °, the received signal intensity due to the direct wave is hardly changed, but the influence of multipath is affected by the change in the path difference between the direct wave and the indirect wave. As shown in FIG. 6, there is a significant difference in the signal strength of the received signal corresponding to each directivity as shown in FIG. In this way, the direction detection unit 60 in the RFID tag communication device 12 compares the received signals corresponding to the respective directivity directions by shifting the directivity direction of the array antenna 16 within the range of 1 to 2 °. Thus, the directivity direction corresponding to the angle with less influence of the multipath is determined. The deviation angle is preferably set to be equal to or smaller than an allowable error angle in detecting the direction of the wireless tag 14.

  Specifically, the direction detection unit 60 sets the first angle by a predetermined angle by the directivity control unit 54 (for example, by 10 ° from −40 ° to 40 ° with respect to the reference direction). A reception signal received in the case where the directivity direction corresponding to the first angle is changed while changing stepwise or the signal intensity thereof, and a predetermined deviation angle (for example, about 1 to 2 °) from the first angle ) The direction of the wireless tag 14 is detected by comparing the received signal received in the case of the directivity direction corresponding to the shifted second angle or the signal intensity thereof. Preferably, first, the directivity control unit 54 changes the transmission directivity and / or reception directivity of the array antenna 16 to the respective first angles while changing the first angle step by step by a predetermined angle. The received signal received in the case of the corresponding directivity direction or the signal strength thereof is stored in a storage device such as the I-phase memory unit 38 and / or the Q-phase memory unit 44, and then the first angle is set. Corresponding to the second angle obtained by shifting the transmission directivity and / or reception directivity of the array antenna 16 by a predetermined deviation angle from each first angle by the directivity control unit 54 while changing the predetermined angle step by step. The received signal or the signal strength received in the case of the directivity direction is stored in the storage device such as the I-phase memory unit 38 and / or the Q-phase memory unit 44 and stored in the storage device. Detecting the direction of the wireless tag 14 by comparing reads the signal signal or the signal strength thereof. In other words, first, in response to the first angle, the directivity control unit 54 changes the directivity of the array antenna 16 one by one through the predetermined angle range within the predetermined angle range, thereby receiving the received signal or its signal strength. Then, the directivity control unit 54 changes the directivity of the array antenna 16 in steps of the predetermined angle within the predetermined angle range corresponding to the second angle, and receives the received signal or Control to store the signal intensity is performed. Further, in the control corresponding to the second angle, preferably, the result of the control corresponding to the first angle previously performed is considered, and a part of the control is performed as will be described later with reference to FIG. Be omitted. Hereinafter, the direction detection control of the wireless tag 14 will be described with reference to the flowcharts of FIGS. In the control shown in the flowcharts of FIGS. 8 to 14, common steps are denoted by the same reference numerals, and description thereof is omitted.

  The direction detection unit 60 preferably uses the signal for each received signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 corresponding to the first angle and the second angle, respectively. The detection results detected by the intensity detection unit 56 are compared with each other, and the direction corresponding to the transmission directivity and / or reception directivity at which the detection result takes the maximum value is detected as the direction of the wireless tag 14. FIG. 8 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, and is repeatedly executed at a predetermined cycle.

In the control of FIG. 8, first, in step (hereinafter, step is omitted) S1, an angle θ indicating the directivity direction is set to an initial value θ _start . Next, in S2, the transmission phase shifter 62 and / or the reception phase shifter 70 are set so that the angle indicating the directivity direction is θ, and the transmission signal is directed toward the wireless tag 14 that is the detection target. And a transmission / reception process for receiving a reply signal returned from the wireless tag 14 in response to the transmission signal. Next, in S3, the signal strength of the received signal received by the transmission / reception processing in S2 is detected, and the detection result _Sθ is stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44. Next, in S4, it is determined whether or not the angle θ indicating the directivity direction is a predetermined value θ _end . When the determination at S4 is negative, after Δθ is added to the angle θ indicating the directivity direction at S5, the processing after S2 is executed again, but when the determination at S4 is positive. In S6, the angle θ indicating the directivity direction is set to θ _start which is an initial value. Next, in S7, the transmission phase shifter 62 and / or the reception phase shifter 70 are set so that the angle indicating the directivity direction becomes θ + 1, and the transmission signal is directed toward the wireless tag 14 that is the detection target. And a transmission / reception process for receiving a reply signal returned from the wireless tag 14 in response to the transmission signal. Next, in S8, the signal strength of the received signal received by the transmission / reception processing in S7 is detected, and the detection result _{Sθ + 1} is stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44. The Next, in S9, it is determined whether or not the angle θ indicating the directivity direction is a predetermined value θ _end . If the determination in S9 is negative, after Δθ is added to the angle θ indicating the directivity direction in S10, the processing from S7 is executed again, but the determination in S9 is positive. In S11 corresponding to the operation of the direction detection unit 60, the received signal strengths S _θ and S _{θ + 1} stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 are read and compared. Then, after θ corresponding to the received signal strength having the maximum value is detected as the direction of the wireless tag 14, this routine is terminated. In the above control, S2 and S7 correspond to the operation of the directivity control unit 54, and S3 and S8 correspond to the operation of the signal intensity detection unit 56, respectively.

In addition, the direction detection unit 60 preferably applies to each reception signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 corresponding to the first angle and the second angle, respectively. The detection results detected by the signal intensity detection unit 56 are compared with each other, and the detection result is a predetermined threshold value in both the directivity direction corresponding to the first angle and the directivity direction corresponding to the second angle. The direction corresponding to the transmission directivity and / or reception directivity as described above is detected as the direction of the wireless tag 14. FIG. 9 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, and is repeatedly executed at a predetermined cycle. When the determination of S9 described above is affirmed in this control, the received signal strength stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 in S12 corresponding to the operation of the direction detection unit 60. S _θ and S _{θ + 1} are read and compared, and after the direction corresponding to the angle θ that is equal to or greater than the predetermined threshold A is detected as the direction of the wireless tag 14, the routine is terminated. It is done.

In addition, the direction detection unit 60 preferably applies to each reception signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 corresponding to the first angle and the second angle, respectively. The detection results detected by the signal intensity detection unit 56 are compared, and the difference between the detection result of the directivity direction corresponding to the first angle and the detection result of the directivity direction corresponding to the second angle is the smallest. The direction corresponding to the angle is detected as the direction of the wireless tag 14. FIG. 10 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, and is repeatedly executed at a predetermined cycle. If the determination of S9 described above is affirmed in this control, the received signal strength stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 in S13 corresponding to the operation of the direction detection unit 60. S _θ and S _{θ + 1} are read to calculate the corresponding differences between S _θ and S _{θ + 1} , respectively, and the direction corresponding to the smallest angle θ is detected as the direction of the wireless tag 14. Thereafter, this routine is terminated.

In addition, the direction detection unit 60 preferably applies to each reception signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 corresponding to the first angle and the second angle, respectively. The detection results detected by the signal intensity detector 56 for each of the directivity direction corresponding to the first angle and the directivity direction corresponding to the second angle are averaged, and the directivity corresponding to the average large angle The direction corresponding to the transmission directivity and / or reception directivity at which the detection result has the maximum value in the direction is detected as the direction of the wireless tag 14. FIG. 11 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, and is repeatedly executed at a predetermined cycle. If the determination in S9 described above is affirmed in this control, the received signal strength stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 in S14 corresponding to the operation of the direction detection unit 60. S _θ, S θ _{+ 1} is read and S _θ, S θ _{+ 1} average value for each (arithmetic mean) is calculated, S _theta, of S _{theta + 1} received in person the average value is larger After the direction corresponding to the angle θ at which the signal intensity takes the maximum value is detected as the direction of the wireless tag 14, this routine is terminated.

In addition, the direction detection unit 60 preferably excludes the direction based on the direction in which the obstacle is detected by the obstacle direction detection unit 58 or the direction set in the obstacle direction setting unit 59, for example. Then, the direction of the wireless tag 14 is detected. FIG. 12 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, and is repeatedly executed at a predetermined cycle. If the determination in S9 described above is affirmed in this control, the reception stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 in S15 corresponding to the operation of the obstacle direction detection unit 58. The signal intensities S _θ and S _{θ + 1} are read out, and the received signal intensities S _θ and S _{θ + 1} are compared to detect (determine) the direction in which the obstacle exists. Next, in S16 corresponding to the operation of the direction detection unit 60, it corresponds to the obstacle direction detected in S15 or an angle range that is more than a predetermined angle away from the direction set in the obstacle direction setting unit 59. S _θ and S _{θ + 1} are compared, and the direction corresponding to the angle θ corresponding to the maximum received signal strength is detected as the direction of the wireless tag 14, and then this routine is terminated.

In addition, preferably, the direction detection unit 60 preferably receives the first signal intensity S _{θ of the} received signal when the directivity direction corresponds to the first angle is equal to or less than a predetermined value. Detection of received signal strength _{Sθ + 1} corresponding to a second angle shifted from the angle of 1 by a predetermined deviation angle, that is, directivity control and transmission and / or reception control of the radio signal are omitted. FIG. 7 is a diagram for explaining such control, and an angle of −20 ° where the signal intensity S _{θ of the} received signal received when the directivity direction corresponds to the first angle is equal to or less than a predetermined value. For 30 ° and 40 °, detection of the received signal strength S _{θ + 1} corresponding to the second angles −21 °, 29 °, and 39 ° is omitted. FIG. 13 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, and is repeatedly executed at a predetermined cycle. In this control, in S17 following the process of S6 described above, the received signal strength _Sθ stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 corresponding to the angle θ at that time is read. Then, it is determined whether or not the received signal strength _Sθ is equal to or greater than a predetermined value. If the determination in S17 is affirmative, the above-described processing from S7 is executed. If the determination in S17 is negative, the above-described processing from S9 is executed. If the determination in S9 is affirmative, the received signal strength S _θ stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 in S18 corresponding to the operation of the direction detection unit 60. , S _{θ + 1} is read, and the direction of the wireless tag 14 is detected by comparing the received signal strengths S _θ and S _{θ + 1} , and then this routine is terminated.

Further, the direction detection unit 60 preferably changes the frequency of the carrier wave of the transmission signal, that is, the frequency of the carrier wave generated by the carrier wave generation unit 20, and compares the received signal received corresponding to each frequency. Then, the direction of the wireless tag 14 is detected. FIG. 14 is a flowchart for explaining a main part of the tag direction detection control of such an aspect, which is repeatedly executed at a predetermined cycle. In this control, first, in S19, the frequency setting value f of the carrier wave which is generated by the carrier wave generating unit 20 after being as f _1, S1 following processing is executed. If the determination in S9 is affirmed, it is determined in S20 whether or not the frequency set value f of the carrier wave generated by the carrier wave generation unit 20 is _fend . If the determination at S20 is negative, after Sf21 adds Δf to the frequency setting value f, the processing after S1 is executed again, but when the determination at S20 is affirmative, In S22 corresponding to the operation of the direction detection unit 60, the received signal strengths _Sθ and _{Sθ + 1} stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44 are read, and the received signal strengths S _theta, after the direction of the wireless tag 14 is detected by comparing the S _{theta + 1,} the present routine is terminated.

  Thus, according to the present embodiment, a plurality of antenna elements 26 are used for transmitting a radio signal to the radio tag 14 that is a radio terminal and / or for receiving a radio signal from the radio tag 14. A directivity control unit 54 (S2 and S7) that controls the transmission directivity and / or the reception directivity of the array antenna 16 by controlling the phase corresponding to each of the array antenna 16 and the plurality of antenna elements 26. ), And a reception signal received by the directivity control unit 54 when the transmission directivity and / or reception directivity of the array antenna 16 is set to the directivity direction corresponding to the first angle, and the first By comparing the received signal received in the case of the directivity direction corresponding to the second angle shifted by a predetermined deviation angle from the angle, the wireless tag 14 Since the direction detection unit 60 (S11, S12, S13, S14, S16, S18, S22) for detecting the direction is provided, the received signal is compared to handle an angle with less influence of multipath. By using the reception result in the directivity direction to be detected, the direction of the wireless tag 14 can be suitably detected. That is, it is possible to provide a direction detection device that reduces the influence of multipath and realizes suitable direction detection.

  In addition, a signal strength detector 56 (S3 and S8) for detecting the signal strength of the received signal received by the array antenna 16 is provided, and the direction detector 60 adjusts the signal strength detected by the signal strength detector. Accordingly, since the direction of the wireless tag 14 is detected, the direction of the wireless tag 14 can be detected in a practical manner.

  Further, the direction detection unit 60 receives the received signal or the signal strength thereof when the first angle is changed step by step by a predetermined angle and the directivity direction corresponding to the first angle is set. The received signal received in the case of the directivity direction corresponding to the second angle or the signal strength thereof is stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44, which is a storage device, Since the direction of the wireless tag 14 is detected by comparing the received signal stored in the storage device or its signal strength, the directivity direction corresponding to the angle with less influence of the multipath is used in a practical manner. The direction of the wireless tag 14 can be detected suitably.

  Further, since the deviation angle is 1/10 or more and 1/5 or less of a predetermined angle that is a stepwise change in the first angle, the directivity direction of the array antenna 16 is compared with the predetermined angle. By comparing the received signal corresponding to each directivity direction by shifting by a sufficiently small deviation angle, it is possible to determine the directivity direction corresponding to the angle with less influence of multipath, and the direction of the wireless tag 14 is changed. It can detect suitably.

  Further, since the deviation angle is in the range of 1 to 2 °, the directivity direction of the array antenna 16 is shifted within the range of 1 to 2 °, and the received signals corresponding to the directivity directions are compared. Thus, it is possible to determine the directivity direction corresponding to the angle with less influence of the multipath, and the direction of the wireless tag 14 can be suitably detected.

  In addition, since the deviation angle is equal to or smaller than an allowable error angle in the direction detection of the wireless tag 14, the directivity direction of the array antenna 16 is shifted within a range equal to or smaller than the allowable error angle in the direction detection. By comparing the corresponding received signals, it is possible to determine the directivity direction corresponding to the angle with less influence of the multipath, and it is possible to suitably detect the direction of the wireless tag 14.

  Further, the direction detection unit 60 first changes the transmission directivity and / or reception directivity of the array antenna 16 by the directivity control unit 54 while changing the first angle step by step by a predetermined angle. The received signal received in the case of the directivity direction corresponding to the first angle or the signal strength thereof is stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44, and then the first angle The directivity control unit 54 changes the transmission directivity and / or reception directivity of the array antenna 16 to a second angle that is shifted from the first angle by a predetermined deviation angle. The received signal received in the case of the corresponding directivity direction or the signal strength thereof is stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44, and the I-phase memory unit 38 and / or Since the direction of the wireless tag 14 is detected by comparing the received signal stored in the phase memory unit 44 or its signal strength, a directivity direction corresponding to an angle with less influence of multipath is practical. The direction of the wireless tag 14 can be suitably detected.

  In addition, when the signal strength of the received signal received when the direction detection unit 60 sets the directivity direction corresponding to the first angle is equal to or less than a predetermined value, the direction detection unit 60 determines a predetermined value from the first angle. Direction that cannot perform suitable communication due to the presence of an obstacle because directivity control corresponding to the second angle shifted by the deviation angle and transmission and / or reception control of the wireless signal are not performed. By omitting the control corresponding to the second angle, the time required for detecting the direction of the wireless tag 14 can be shortened.

  The direction detection unit 60 (S11) compares the detection results detected by the signal intensity detection unit 56 for each received signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44. Since the direction corresponding to the transmission directivity and / or reception directivity at which the detection result takes the maximum value is detected as the direction of the wireless tag 14, the direction of the wireless tag 14 is determined in a practical manner. Can be detected.

  The direction detection unit 60 (S12) compares the detection results detected by the signal intensity detection unit 56 for each received signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44, A direction corresponding to the transmission directivity and / or the reception directivity in which the detection result is equal to or greater than a predetermined threshold in both the directivity direction corresponding to the first angle and the directivity direction corresponding to the second angle. Since the direction of the wireless tag 14 is detected, the direction of the wireless tag 14 can be detected in a practical manner.

  The direction detection unit 60 (S13) compares the detection results detected by the signal intensity detection unit 56 for each received signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44. Detecting the direction corresponding to the angle with the smallest difference between the detection result of the directivity direction corresponding to the first angle and the detection result of the directivity direction corresponding to the second angle as the direction of the wireless tag 14 Therefore, the direction of the wireless tag 14 can be detected in a practical manner.

  In addition, the direction detection unit 60 (S14) has a directivity direction and a second angle corresponding to the first angle for each received signal stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44. The detection results detected by the signal intensity detection unit 56 with respect to each of the directivity directions corresponding to the transmission direction and / or the transmission directivity where the detection result takes the maximum value in the directivity direction corresponding to the average large angle and / or Since the direction corresponding to the reception directivity is detected as the direction of the wireless tag 14, the direction of the wireless tag 14 can be detected in a practical manner.

  Further, an obstacle direction detection unit 58 (S15) for detecting the direction in which the obstacle exists by comparing the received signals or signal strengths stored in the I-phase memory unit 38 and / or the Q-phase memory unit 44. The direction detection unit 60 (S16) excludes the direction in which the obstacle is detected by the obstacle direction detection unit 58 or the direction set in the obstacle direction setting unit 59, and removes the direction of the wireless tag 14. Since the direction is detected, the direction of the wireless tag 14 can be suitably detected by avoiding the direction in which the obstacle causing the multipath occurs.

  In addition, the direction detection device transmits a predetermined transmission signal toward the wireless tag 14 that is a detection target, and receives a reply signal returned from the wireless tag 14 in response to the transmission signal. Since the wireless tag communication device (wireless tag direction detection device) 12 detects the direction of the wireless tag 14, the wireless tag communication device 12 that realizes a preferable direction detection of the wireless tag 14 by reducing the influence of multipath is provided. can do.

  The direction detection unit 60 (S22) detects the direction of the wireless tag 14 by changing the frequency of the carrier wave of the transmission signal and comparing the received signals received corresponding to each frequency. Therefore, by comparing the received signals received corresponding to each directivity direction in each of a plurality of carrier frequencies, and using the reception result by the carrier frequency with less influence of multipath, the direction of the wireless tag 14 is further changed. It can detect suitably.

  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 directivity control unit 54, the signal intensity detection unit 56, the obstacle direction detection unit 58, the direction detection unit 60, and the like are all provided individually. The invention is not limited to this, and a control function equivalent to these is functionally provided in a DSP (Digital Signal Processor) that includes a CPU, ROM, RAM, etc., and executes digital signal processing. It doesn't matter. The control by these control devices may be digital signal processing or analog signal processing.

  In the above-described embodiment, each of the antenna elements 26 provided in the RFID tag communication device 12 is a linear antenna element such as a dipole antenna, and a plurality of sets of arrays are formed from the plurality of linear antenna elements 26. Although the antenna 16 is configured, for example, an array antenna may be configured by a flat (planar) antenna element such as a patch antenna, and the present invention is also applied to a communication apparatus including such an antenna. Can be suitably applied.

  In the above-described embodiment, the received signal received when the directivity direction corresponds to a single second angle that is shifted from the first angle by a predetermined deviation angle for each of the first angles. The aspect of detecting the direction of the wireless tag 14 by detecting and comparing the received signal corresponding to the second angle and the received signal corresponding to the first angle has been described. When the angle is θ, the angle θ ± 1 is set as the second angle, and the second angle is shifted from the first angle by a predetermined deviation angle for each first angle. The wireless tag 14 is detected by detecting a received signal received in the case of a corresponding directivity direction and comparing the received signal corresponding to the plurality of second angles with the received signal corresponding to the first angle. May detect the direction ofIn this way, it is possible to reduce the influence of multipath as much as possible and realize more suitable direction detection.

  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 example in which the present invention is applied to the RFID tag communication apparatus 12 having the shared array antenna 16 having 26 is described, a transmission antenna for transmitting the transmission signal and a reception antenna for receiving the reception signal The present invention is also preferably applied to a wireless tag communication device provided separately.

  In the above-described embodiment, a predetermined transmission signal is transmitted toward the wireless tag 14 that is a communication target, and a reply signal that is returned from the wireless tag 14 in response to the transmission signal is received. The example in which the present invention is applied to the wireless tag communication device 12 that communicates information with the wireless tag 14 has been described. However, for example, a communication terminal in another wireless communication device such as a mobile phone or a mobile communication device The present invention can be preferably applied to the direction detection.

  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 direction detection apparatus of this invention is used suitably. It is a figure explaining the structure of the RFID tag communication apparatus which is a suitable Example of the direction detection apparatus of this invention. It is a figure explaining in detail the structure of the transmission / reception module with which the RFID tag communication apparatus of FIG. 2 was equipped. FIG. 3 is a diagram illustrating a configuration of a wireless tag circuit element provided in a wireless tag that is a wireless terminal to be detected by the wireless tag communication device of FIG. 2. It is a figure explaining the multipath which generate | occur | produces when the RFID tag communication system of FIG. 1 is operate | moved indoors. The signal strength of the received signal received when the first angle is changed step by step by a predetermined angle by the RFID tag communication apparatus of FIG. 2 and the directivity direction corresponding to the first angle is set. It is a figure which contrasts with the signal strength of the received signal received when it is set as the directivity direction corresponding to the 2nd angle shifted | deviated the predetermined deviation angle from this angle. In the direction detection control by the RFID tag communication apparatus of FIG. 2, when the signal intensity of the received signal received when the directivity direction corresponding to the first angle is less than or equal to a predetermined value, the first angle is It is a figure explaining not performing the directivity control corresponding to the 2nd angle shifted by the predetermined deviation angle, and transmission and / or reception control of a radio signal. 3 is a flowchart for explaining a main part of an example of tag direction detection control by the wireless tag communication device of FIG. 2. 6 is a flowchart for explaining a main part of another example of tag direction detection control by the wireless tag communication device of FIG. 2. 6 is a flowchart for explaining a main part of still another example of tag direction detection control by the wireless tag communication device of FIG. 2. 6 is a flowchart for explaining a main part of still another example of tag direction detection control by the wireless tag communication device of FIG. 2. 6 is a flowchart for explaining a main part of still another example of tag direction detection control by the wireless tag communication device of FIG. 2. 6 is a flowchart for explaining a main part of still another example of tag direction detection control by the wireless tag communication device of FIG. 2. It is a figure explaining the structure of the RFID tag communication apparatus which is another suitable Example of the direction detection apparatus of this invention.

Explanation of symbols

12: RFID tag communication device (direction detection device)
14: Wireless tag (wireless terminal)
16: Array antenna 26: Antenna element 38: I-phase memory unit (storage device)
44: Q-phase memory unit (storage device)
54: Directivity control unit 56: Signal intensity detection unit 58: Obstacle direction detection unit 59: Obstacle direction setting unit 60: Direction detection unit 92: Wall (obstacle)

Claims (15)

A direction detection device that transmits and / or receives a radio signal to a radio terminal and detects the direction of the radio terminal based on the radio signal,
An array antenna composed of a plurality of antenna elements for transmitting a radio signal to the radio terminal and / or for receiving a radio signal from the radio terminal;
A directivity control unit that controls the transmission directivity and / or reception directivity of the array antenna by controlling the phase corresponding to each of the plurality of antenna elements;
A reception signal received by the directivity control unit when the transmission directivity and / or reception directivity of the array antenna is a directivity direction corresponding to the first angle, and a predetermined deviation from the first angle A direction detection unit that detects a direction of the wireless terminal by comparing a received signal received in the case of the directivity direction corresponding to the second angle shifted by an angle. A characteristic direction detection device.   A signal strength detection unit configured to detect a signal strength of a reception signal received by the array antenna, wherein the direction detection unit detects a direction of the wireless terminal according to the signal strength detected by the signal strength detection unit; The direction detection device according to claim 1.   The direction detection unit receives the received signal or its signal strength when the first angle is changed stepwise by a predetermined angle and is set to a directivity direction corresponding to the first angle, and the second The received signal or its signal strength received in the direction of directivity corresponding to the angle is stored in a predetermined storage device, and the received signal or its signal strength stored in the storage device is compared. The direction detection device according to claim 2, which detects a direction of the wireless terminal.   The direction detection device according to claim 3, wherein the deviation angle is not less than 1/10 and not more than 1/5 of a predetermined angle that is a stepwise change of the first angle.   5. The direction detection device according to claim 1, wherein the deviation angle is in a range of 1 to 2 degrees.   6. The direction detection device according to claim 1, wherein the deviation angle is equal to or smaller than an allowable error angle in direction detection of the wireless terminal.   The direction detection unit first changes the transmission directivity and / or reception directivity of the array antenna to the respective first angles by the directivity control unit while changing the first angle step by step by a predetermined angle. The received signal received in the case of the corresponding directivity direction or the signal strength thereof is stored in the storage device, and then the directivity control unit changes the first angle step by step by a predetermined angle. Received signal or signal strength received when the array antenna has a transmission directivity and / or a reception directivity that is a directivity direction corresponding to a second angle shifted from the first angle by a predetermined deviation angle. 7 is stored in the storage device, and the direction of the wireless terminal is detected by comparing the received signal stored in the storage device or the signal strength thereof. Direction detecting device.   The direction detecting unit shifts a predetermined deviation angle from the first angle when the signal strength of the received signal received when the directivity direction corresponding to the first angle is equal to or less than a predetermined value. The direction detection device according to claim 7, wherein directivity control corresponding to the second angle and transmission and / or reception control of the wireless signal are not performed.   The direction detection unit compares the detection results detected by the signal intensity detection unit for each received signal stored in the storage device, and transmits and / or receives directivity at which the detection result takes a maximum value. The direction detection device according to any one of claims 2 to 8, wherein a direction corresponding to a sex is detected as a direction of the wireless terminal.   The direction detection unit compares a detection result detected by the signal intensity detection unit for each received signal stored in the storage device, and the detection result corresponds to a directivity direction corresponding to the first angle and a second direction. The direction corresponding to the transmission directivity and / or the reception directivity that is equal to or greater than a predetermined threshold in any of the directivity directions corresponding to the angle is detected as the direction of the wireless terminal. Direction detector.   The direction detection unit compares the detection result detected by the signal intensity detection unit for each received signal stored in the storage device, and the detection result of the directivity direction corresponding to the first angle and the second 9. The direction detection device according to claim 2, wherein the direction corresponding to the angle having the smallest difference from the detection result of the directivity direction corresponding to the angle is detected as the direction of the wireless terminal.   The direction detection unit is detected by the signal intensity detection unit for each of the received signals stored in the storage device with respect to the directivity direction corresponding to the first angle and the directivity direction corresponding to the second angle. The detection result is averaged, and the direction corresponding to the transmission directivity and / or the reception directivity at which the detection result has the maximum value in the directivity direction corresponding to the average large angle is detected as the direction of the wireless terminal. The direction detection device according to any one of claims 2 to 8.   An obstacle direction detector that detects the direction in which an obstacle exists by comparing each received signal or signal strength stored in the storage device, or an obstacle direction that sets the direction of the obstacle when the direction is known A setting unit, wherein the direction detection unit detects the direction of the wireless terminal excluding the direction in which the obstacle is detected by the obstacle direction detection unit or the direction set in the obstacle direction setting unit. The direction detection device according to claim 1, wherein the direction detection device is a device.   The direction detection device transmits a predetermined transmission signal toward the detection target wireless tag, and receives a return signal returned from the wireless tag in response to the transmission signal, whereby the direction of the wireless tag The direction detection device according to any one of claims 1 to 13, wherein the direction detection device is a wireless tag direction detection device.   15. The direction detection according to claim 14, wherein the direction detection unit detects a direction of the wireless tag by changing a frequency of a carrier wave of the transmission signal and comparing a reception signal received corresponding to each frequency. apparatus.

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