JP2008164379A - Radio tag communication apparatus and radio tag communication system - Google Patents

Abstract

A wireless tag communication device that realizes a practical security system with a simple configuration is provided.
A directivity control unit that controls the directivity of communication with a wireless tag and a predetermined signal based on a return signal from the wireless tag in each directivity determined by the directivity control unit. Since the communication state change detection unit 66 for detecting a change in the communication state in the area is provided, communication with the wireless tag 14 due to movement of the moving body 94 as a radio wave shielding object or a radio wave reflection object is provided. By observing the inhibition and the formation of multipaths, it is possible to easily detect the movement of the moving body 94 within a predetermined region.
[Selection] Figure 2

Description

  The present invention relates to a wireless tag communication device and a wireless tag communication system for performing wireless communication of information with a wireless tag, and more particularly to a security system using communication with such a wireless tag.

  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 a wireless tag communication system using such a wireless tag communication apparatus, a security system using communication with the wireless tag has been proposed. For example, this is the detection system described in Patent Document 1. According to this technique, the microwave device is provided with a recognition device that is attached to an arbitrary place of the authorizer entering and exiting the radio wave radiation area, detects a radio wave radiated from the microwave sensor, and transmits a signal for authorizer recognition. Since the sensor detects the signal from the recognition device, it is said that the person authorized by the simple device and the suspicious person can be discriminated and the suspicious person can quickly detect the intrusion into the warning spot. Yes.

Japanese Patent No. 3763454

  However, as described above, the conventional security system using the wireless tag communication detects the recognizer by communicating with the recognition tag carried by the authorizer. The suspicious person who is assumed not to have not been detected properly. In addition, as a system for detecting the movement of a person or an object within a predetermined area, there are a radar device and an infrared sensor using electromagnetic waves, but the radar device is relatively expensive and is located near or inside a building. When using, the reflected wave from an adjacent building or building wall surface is received, so that there is a problem that it is difficult to identify the object to be detected. Moreover, although an infrared sensor is comparatively cheap, it can detect only a predetermined narrow detection range because of its configuration, and is difficult to apply to detection in a spatially wide area. For this reason, the development of a technology for realizing a practical security system with a simple configuration has been demanded.

  The present invention has been made against the background of the above circumstances, and its object is to provide a wireless tag communication device and a wireless tag communication system that realize a practical security system with a simple configuration. is there.

  In order to achieve such an object, the gist of the first invention is that a transmission signal is transmitted from a transmission antenna toward a wireless tag, and a reply signal is returned from the wireless tag according to the transmission signal. Is a wireless tag communication device that performs communication of information with the wireless tag by receiving the signal with a reception antenna, a directivity control unit that controls the directivity of communication with the wireless tag, and the directivity A communication state change detecting unit for detecting a change in communication state within a predetermined area based on a return signal from the wireless tag in each directivity determined by the sex control unit. .

  In order to achieve the above object, the gist of the second invention is that information is transferred between the RFID tag arranged in a predetermined area using the RFID tag communication apparatus of the first invention. The wireless tag communication system is characterized by detecting a change in a communication state in the region by performing communication.

  As described above, according to the first aspect of the present invention, the directivity control unit that controls the directivity of communication with the wireless tag, and the reply from the wireless tag in each directivity determined by the directivity control unit. A communication state change detection unit that detects a change in communication state within a predetermined area based on a signal, and thus the wireless tag by movement of a moving body as a radio wave shielding object or a radio wave reflection object; By observing the inhibition of communication between them, the formation of multipaths, etc., it is possible to easily detect the movement of the moving body in the region. That is, it is possible to provide a wireless tag communication device that realizes a practical security system with a simple configuration.

  Here, the first invention preferably includes a reception signal strength detection unit that detects a signal strength of a reception signal received by the reception antenna, and the communication state change detection unit includes the reception signal strength detection unit. The change of the communication state in the area is detected based on the signal strength of the received signal detected by the above. In this way, it is possible to detect a change in the communication state within the target region in a practical manner.

  Preferably, the communication state change detecting unit detects a change in communication state in the region based on an average value of signal strengths of received signals detected by the received signal strength detecting unit. In this way, by comparing with the average value of the signal strength of the received signal, it is possible to absorb fluctuations in the received signal strength such as fading due to variations in detection of the received signal strength and steady environmental changes in the region. In this manner, it is possible to detect a change in the communication state within the target region.

  Preferably, the communication state change detection unit includes a signal strength of the reception signal detected by the reception signal strength detection unit and a signal strength of the reception signal detected last time by the reception signal strength detection unit. By comparing, the change of the communication state in the area is detected. In this way, it is possible to detect a change in the communication state within the target region in a practical manner by comparing with the signal strength of the previous received signal.

  Preferably, the wireless tag further includes a carrier strength control unit that controls the strength of the carrier wave of the transmission signal, and the communication state change detection unit is configured to respond to each carrier whose strength is changed by the carrier strength control unit. The change of the communication state in the area is detected by comparing the return signals sent back from each other. In this way, it is possible to improve the resolution for detecting the change in the communication state in the target region by comparing the received signals corresponding to the transmission signals having different intensities.

  Preferably, the wireless tag communication device communicates information with a plurality of the wireless tags, and the communication state change detection unit is based on return signals from the plurality of wireless tags. Thus, a change in communication state within the area is detected. In this way, the area to be detected can be expanded by increasing the number of wireless tags that perform communication.

  Preferably, at least one of the transmission antenna and the reception antenna is an array antenna having a plurality of antenna elements, and the directivity control unit includes the transmission directivity of the transmission signal and the reception directivity of the reception signal. At least one is controlled. In this way, it is possible to control the directivity of communication with the wireless tag in a practical manner, and the communication within the target region based on the return signal from the wireless tag in each directivity. A change in the state can be suitably detected.

  Preferably, intrusion of the moving body into the area is detected based on a change in communication state detected by the communication state change detection unit. In this way, it is possible to realize a security system that detects the intrusion of a moving object such as a suspicious person into the target area.

  Preferably, the movement of the moving body in the region is detected based on a change in communication state detected by the communication state change detection unit. In this way, it is possible to realize a security system that detects the movement of a moving object such as a suspicious person in a target area.

  Further, according to the second invention, information is communicated with a radio tag arranged in a predetermined area using the radio tag communication apparatus of the first invention, whereby a communication state in the area is communicated. Because it is characterized by detecting changes in the frequency, observation of obstruction of communication with the wireless tag due to movement of a mobile object as a radio wave shield or radio wave reflector, formation of multipaths, etc. Thus, the movement of the moving body within the region can be easily detected. That is, it is possible to provide a wireless tag communication system that realizes a practical security system with a simple configuration.

  Here, the second invention preferably includes a plurality of the RFID tag communication devices, and detects a change in a communication state in the region by the plurality of RFID tag communication devices. In this way, it is possible to more suitably detect the movement of the moving body within the region using a plurality of RFID tag communication devices.

  Preferably, the plurality of wireless tag communication devices alternately communicate information with the wireless tag. In this way, batting of communication with a predetermined wireless tag by the plurality of wireless tag communication devices can be suitably prevented.

  Preferably, a plurality of the wireless tags are provided in a fixed position in the area. In this way, it is possible to detect a change in the communication state in the area in a practical manner by comparing the received signals corresponding to the plurality of wireless tags whose relative positions with respect to the area are fixed.

  Preferably, the plurality of wireless tags are provided in different directions with respect to the wireless tag communication device. In this way, a change in the communication state in the region is detected in a practical manner by comparing received signals corresponding to a plurality of wireless tags whose relative directions with respect to the wireless tag communication device are fixed. Can do.

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

FIG. 1 is a diagram for explaining a radio tag communication system 10 according to an embodiment of the second invention. The RFID tag communication system 10 includes one or more (single in FIG. 1) RFID tag communication apparatuses 12 according to an embodiment of the first invention, and the singular or the communication target of the RFID tag communication apparatus 12. It is a so-called RFID (Radio Frequency Identification) system composed of a plurality (single in FIG. 1) of wireless tags 14, wherein the wireless tag communication device 12 is an interrogator of the RFID system, and the wireless tag 14 is a responder. Each functions. 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. As will be described later, the RFID tag communication system 10 communicates information with the RFID tag 14 disposed in a predetermined area by the RFID tag communication device 12 so that the communication state in the area is determined. A security system is configured to detect a change and detect the movement of the moving body within the region in accordance with the change.

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 according to the present embodiment outputs a transmission data as a digital signal, or executes a digital signal processing such as demodulating a return signal from the RFID tag 14 (DSP ( Digital Signal Processor) 16, a carrier wave oscillating unit 18 that oscillates and outputs a carrier wave of the transmission signal, and a transmission multiplication unit that outputs the carrier wave output from the carrier wave oscillating unit 18 with transmission data supplied from the DSP 16 20 and the signal output from the transmission multiplier 20 as the interrogation wave F _c , and the radio tag communication for receiving the response wave F _r returned from the radio tag 14 according to the transmission signal A plurality (three in FIG. 2) of antenna elements 22a, 22b, and 22c (hereinafter, unless otherwise distinguished) provided in a fixed position on the apparatus main body of the apparatus 12. And the antenna element 22 for transmission / reception and the phase of the transmission signal output from the transmission multiplication unit 20 corresponding to each antenna element 22 and outputting the same, and each antenna element A phased array antenna (PAA) processing unit 26 that controls and outputs the phase of the received signal received by the signal 22, and a phase-controlled transmission signal output from the PAA processing unit 26 is supplied to each antenna element 22. , A plurality of (three in FIG. 2) transmission / reception separators 28a, 28b, and 28c (hereinafter simply referred to as transmission / reception separators unless otherwise specified) that supply reception signals received by each antenna element 22 to the PAA processing unit 26. 28), a local oscillator 30 that oscillates a predetermined local signal, and each phase-controlled antenna output from the PAA processing unit 26. A plurality of (three in FIG. 2) reception multipliers 32a, 32b, 32c (hereinafter not particularly distinguished) supplied to the DSP 16 by multiplying the reception signal corresponding to the child 22 by the local signal output from the local oscillator 30 In some cases, it is simply referred to as a reception multiplication unit 32). The intensity of the carrier wave output from the carrier wave oscillating unit 18 can be controlled by a control command supplied from the DSP 16. As the transmission / reception separation unit 28, a well-known circulator or the like is preferably used.

  The PAA processor 26 controls a plurality of (three in FIG. 2) transmission phase shifters 34a, 34b, 34c (three in FIG. 2) for controlling the phase of the transmission signal output from the transmission multiplier 20 corresponding to each antenna element 22. Hereinafter, when not particularly distinguished, they are simply referred to as “transmission phase shifters 34”, and a plurality of transmission signals output from the respective transmission phase shifters 34 and supplied to the corresponding transmission / reception separators 28 (3 in FIG. 2). Transmission amplifying units 36a, 36b, 36c (hereinafter simply referred to as transmission amplifying unit 36 unless otherwise distinguished), and received signals supplied by each antenna element 22 and supplied via transmission / reception separating unit 36. A plurality of (three in FIG. 2) reception phase shifters 38a, 38b, and 38c (hereinafter simply referred to as reception phase shifters 38 unless otherwise distinguished) for controlling the phase, and outputs from the respective reception phase shifters 38 Received signal A plurality of (three in FIG. 2) reception amplification units 40a, 40b, and 40c (hereinafter simply referred to as reception amplification unit 40 unless otherwise distinguished) that are amplified and supplied to the corresponding reception multiplication unit 32. Configured. Further, the amount of phase shift in each transmission phase shift unit 34 and reception phase shift unit 38 is configured to be controlled by a control command supplied from a directivity control unit 54 described later.

  The DSP 16 includes a CPU that is a central processing unit, a ROM that is a read-only memory, a RAM that is a read / write memory as needed, and a signal according to a program stored in advance in the ROM while using a temporary storage function of the RAM. This is a so-called microcomputer that performs processing, and in addition to various controls related to communication with the wireless tag 14, performs control for realizing a security system by the wireless tag communication system 10 of this embodiment, as will be described later. . In order to perform such control, the carrier strength control unit 50, the transmission data generation unit 52, the directivity control unit 54, the reception signal synthesis unit 60, the reception signal demodulation unit 62, the reception signal strength detection unit 64, and the communication state change detection unit 66 and a suspicious moving body detection unit 68 are functionally provided. In addition, a storage unit 70 such as a RAM or a hard disk capable of storing information is provided.

  The carrier strength controller 50 controls the strength of the carrier generated by the carrier oscillator 18. The transmission data generation unit 52 generates transmission data for the wireless tag 14 and supplies the transmission data to the transmission multiplication unit 20. The transmission data is, for example, a predetermined command bit string, and the transmission multiplying unit 20 outputs the transmission data supplied from the transmission data generating unit 52 on the carrier wave supplied from the carrier wave oscillating unit 18. . The signal thus output is transmitted as a transmission signal from the array antenna 24 via the PAA processing unit 26, the transmission / reception separating unit 28, and the like.

  The directivity control unit 54 controls communication directivity between the array antenna 24 and the wireless tag 14 via the PAA processing unit 26. In order to perform such control, a transmission directivity control unit 56 and a reception directivity control unit 58 are provided. The transmission directivity control unit 56 controls the transmission directivity of the array antenna 24 as a transmission antenna by controlling the amount of phase shift in each transmission phase shift unit 34 in the PAA processing unit 26. The reception directivity control unit 58 controls the reception directivity of the array antenna 24 as a reception antenna by controlling the amount of phase shift in each reception phase shift unit 38 in the PAA processing unit 26. By performing such control, the beam is directed in the main lobe direction corresponding to the directivity direction. The directivity control unit 54 can preferably control the beam width of the beam in each directivity direction in various ways, and changes the beam width in various ways according to the communication mode.

  The reception signal combining unit 60 combines (adds) the reception signals respectively received by the plurality of antenna elements 22. The received signal demodulator 62 demodulates the received signal synthesized by the received signal synthesizer 60. Preferably, after the received signal is AM demodulated by the AM method, the demodulated signal is FM-decoded to read an information signal related to the modulation by the wireless tag 14.

  The reception signal strength detection unit 64 detects the signal strength of the reception signal received by the array antenna 24 as a reception antenna, that is, the signal strength of the reception signal synthesized by the reception signal synthesis unit 60. Preferably, the signal strength of the received signal is detected corresponding to each directivity determined by the directivity control unit 54, and the directivity and signal strength are stored in the storage unit 70 in association with each other.

  The communication state change detection unit 66 detects a change in communication state within a predetermined area based on a return signal from the wireless tag 14 in each directivity determined by the directivity control unit 54. Further, the suspicious mobile body detection unit 68 detects a suspicious mobile body within a predetermined region based on a change in communication state detected by the communication state change detection unit 66. Details of the control by the communication state change detection unit 66 and the suspicious mobile body detection unit 68 will be described later with reference to FIGS.

FIG. 3 is a diagram illustrating the configuration of the RFID circuit element 72 provided in the RFID tag 14. As shown in FIG. 3, 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.

  FIG. 4 is a diagram for explaining a security system using the RFID tag communication system 10 of the present embodiment, and FIG. 5 shows each of the cases where the communication directivity is changed in the RFID tag communication apparatus 12 of FIG. It is a graph which shows the signal strength distribution of the received signal corresponding to a directivity direction. As shown in FIG. 4, the RFID tag communication system 10 communicates information with a RFID tag 14 disposed in a predetermined area, for example, a room 90. The wireless tag communication device 12 and the wireless tag 14 provided are preferably provided in a fixed position relative to the chamber 90. In the wireless tag communication system 10 configured as described above, when the directivity control unit 54 changes the directivity direction of communication between the wireless tag communication device 12 and the wireless tag 14, each directivity is changed. The signal intensity distribution of the received signal corresponding to the direction is, for example, as shown by a solid line in FIG. Regarding this signal intensity distribution, a peak near an angle of 0 ° corresponds to a transmission signal that reaches the wireless tag 14 regardless of reflection, that is, a direct wave communication, and a peak near an angle of ± 70 ° This corresponds to communication by the reflected wave (see FIG. 4) reflected by the 90 wall portions 92.

  Here, as shown in FIG. 4, considering the case where there are mobile bodies 94a and 94b (hereinafter simply referred to as the mobile body 94 unless otherwise distinguished) that can reflect radio waves in the chamber 90, A new radio wave transmission path (multipath) from the RFID tag communication device 12 to the RFID tag 14 is formed by the reflection of the moving body 94a, and a new signal strength distribution of the received signal as shown by a one-dot chain line in FIG. A peak appears. In addition, the transmission of the radio wave by the reflection at the one wall portion 92 of the chamber 90 is blocked by the moving body 94b, and the peak corresponding to the radio wave transmission path disappears as shown by the broken line in FIG. As described above, when the moving body 94 moves in the chamber 90, a change occurs in the communication state between the wireless tag communication device 12 and the wireless tag 14 in the chamber 90. It is reflected in the signal intensity distribution of the received signal as follows. The communication state change detection unit 66 preferably has a predetermined area based on the signal strength of the reception signal detected by the reception signal strength detection unit 64, and more preferably based on the average value of the signal strength, that is, the chamber. A change in the communication state within 90 is detected. That is, the signal strength distribution of the received signal detected by the received signal strength detection unit 64, and the signal strength distribution of the received signal previously detected by the received signal strength detection unit 64 and stored in the storage unit 70, By comparing, the change in the communication state in the chamber 90 is detected. The suspicious moving body detection unit 68 detects the movement of the moving body 94 in the chamber 90 based on the change in the communication state detected by the communication state change detection unit 66. In this way, a simple security system in the room 90 can be realized by the RFID tag communication system 10 of the present embodiment.

  The communication state change detection unit 64 preferably compares the return signal returned from the wireless tag 14 in accordance with each carrier whose strength is changed by the carrier strength control unit 50, thereby comparing the chamber 90. Changes in the communication status within the network are detected. Since the transmittable distance of the transmission signal is basically determined by the strength of the carrier wave, a plurality of types of transmission signals having different transmittable distances can be transmitted by changing the strength of the carrier wave. By comparing the received signals corresponding to the transmission signals having different intensities as described above, it is possible to improve the resolution of detection of a change in the communication state in the target region, that is, the chamber 90, and more preferably the chamber. The movement of the moving body 94 within 90 can be detected.

  FIG. 6 is a diagram illustrating another example of a security system using the wireless tag communication system 10 of the present embodiment. The RFID tag communication system 10 shown in FIG. 6 has a plurality (three in FIG. 6) arranged in different directions (different angular directions as viewed from the RFID tag communication device 12) with respect to the RFID tag communication device 12. Wireless tags 14a, 14b, and 14c (each configuration is equivalent to the wireless tag 14 described above, and hereinafter simply referred to as a wireless tag 14 unless otherwise distinguished). The security system is realized by using the communication. In such a configuration, the communication state change detection unit 66 detects a change in the communication state in the chamber 90 based on return signals from the plurality of wireless tags 14. For example, communication for recognizing (identifying) the plurality of wireless tags 14 is performed, and a change in communication state is detected based on whether or not recognition is possible. FIG. 7 is a table illustrating a recognition result of the plurality of wireless tags 14 by the wireless tag communication system 10 of FIG. In the example shown in FIG. 7, TagA (wireless tag 14a), TagB (wireless tag 14b), and TagC (wireless tag 14c) can be recognized at time t1, but TagC can be recognized at time t2. It is gone. This is because, as shown in FIG. 6, the transmission of radio waves is hindered by the moving body 94 being located in the radio wave transmission path between the radio tag communication device 12 and the radio tag 14c. The movement of the moving body 94 in the chamber 90 can also be suitably detected by communicating information with the plurality of wireless tags 14 and comparing whether the wireless tags 14 can be recognized.

  FIG. 8 is a diagram illustrating still another example of the security system using the wireless tag communication system 10 of the present embodiment. The RFID tag communication system 10 shown in FIG. 8 has a plurality (two in FIG. 8) of RFID tag communication devices 12a and 12b (each configuration is equivalent to the RFID tag communication device 12 described above, and is not particularly distinguished below. In some cases, the wireless tag communication device 12) and a plurality of wireless tags 14a, 14b, and 14c are provided, and a security system is realized using communication between the plurality of wireless tags 14. is there. In such a configuration, a change in the communication state in the chamber 90 is detected by the plurality of RFID tag communication devices 12. Here, preferably, the plurality of RFID tag communication devices 12 alternately communicate information with the RFID tag 14 in order to prevent communication batting. That is, first, the wireless tag communication device 12a communicates with the wireless tags 14a, 14b, and 14c, and after such communication is completed, the wireless tag communication device 12b uses the wireless tags 14a, 14b, and 14c. Communicate with. In addition, as shown in FIG. 9, in the RFID tag communication system 10 configured by including a plurality of RFID tag communication apparatuses 12 a and 12 b and a single RFID tag 14, the plurality of RFID tag communication apparatuses 12 are similarly provided. It is preferable to communicate information with the wireless tag 14 alternately. As described above, by performing communication using the plurality of RFID tag communication devices 12, it is possible to improve the resolution of detection of a change in communication state in a target region, that is, the chamber 90, and more preferably in the chamber 90. The movement of the moving body 94 can be detected.

  FIG. 10 is a diagram illustrating still another example of a security system using the wireless tag communication system 10 of the present embodiment. In the wireless tag communication system 10 shown in FIG. 10, a plurality (two in FIG. 10) of wireless tags 14a and 14b are provided near the entrance 96 of the chamber 90, and the wireless tag communication apparatus 12 The wireless tag 14 communicates with the wireless tag 14 to detect the intrusion of the moving body 94 into the chamber 90 based on the change in the communication state detected by the communication state change detection unit 66. That is, when the mobile body 94 enters the chamber 90, the mobile body 94 passes through the entrance / exit 96, thereby changing the communication environment near the entrance / exit 96, and the wireless tag communication device 12 and the wireless tags 14a, 14b. Changes in the communication state between the two. The wireless tag communication device 12 detects the change in the communication state by the communication state change detection unit 66, thereby moving the moving body 94 in the vicinity of the entrance / exit 96 of the chamber 90, that is, the moving body 94 to the chamber 90. Intrusion can be detected.

  FIG. 11 is a flowchart for explaining a main part of an example of the suspicious mobile object detection control by the DSP 16 of the RFID tag communication apparatus 12 and is repeatedly executed at a predetermined cycle.

First, in step (hereinafter, step is omitted) S1, time t _N is set to t ₁ which is an initial value. Next, in S2, a directivity angle A _Y indicating a directivity direction of communication with the wireless tag 14 is set to A ₁ which is an initial value. Next, in S3, communication is performed with the wireless tag 14, and information stored in the wireless tag 14 is read. Next, in S4 that corresponds to the operation of the received signal strength detector 64, the signal strength of the received signal corresponding to the reply signals from a plurality of RFID tags 14 (tag G ₁ ~G _X) is detected, the directivity angle It is associated with A _Y and stored in the storage unit 70. Next, in S5, the directivity angle A _Y is set to A _{Y + 1} . Next, in S6, it is determined whether or not the directivity angle _AY at that time is a predetermined value _Amax . When the determination at S6 is negative, the processing after S3 is executed again, but when the determination at S6 is affirmative, the time t _N is set to t _{N + 1 at} S7. Next, in S8, it is determined whether or not the time t _N at that time is a predetermined value t _che . If the determination in S8 is negative, the processing from S2 is executed again. If the determination in S8 is positive, in S9, the total received intensity distribution S up to time t _N is stored in the memory. Read from the unit 70. The reception intensity distribution S is a function of time t _N , directivity angle A _Y , and tag G _X. Next, in S10, received intensity distributions S ₁ (G _X , A _Y ) and S ₂ (G _X , A _Y ) at two different times t _N are selected. Next, in S11, whether two received intensities selected distribution S ₁ and S ₂ equal is determined at S10. If the determination in S10 is affirmative, the routine is terminated after it is determined in S12 that there is no abnormality in the chamber 90, but if the determination in S11 is negative, in S13, The movement of the moving body 94 in the chamber 90 and the intrusion of the moving body 94 into the chamber 90 are detected. Next, in S14, after operations such as alarm and camera recording are started, this routine is terminated. In the above processing, S2 and S5 correspond to the operation of the directivity control unit 54, S9 to S11 correspond to the operation of the communication state change detection unit 66, and S12 and S13 correspond to the operation of the suspicious moving body detection unit 68, respectively. .

In the control shown in FIG. 11 described above, the selection of the received intensity distributions S ₁ (G _X , A _Y ) and S ₂ (G _X , A _Y ) in S ₁₀ is, for example, at the time t _N. selection mode for comparing the reception intensity distribution received signal strength at time t _N-1 immediately preceding, i.e. as _{S 1 S (G X, a} Y, t N-1) and, as the S ₂ S (G _X, A mode of selecting A _Y , t _N ) is conceivable. The selection manner for comparing the average of the reception intensity distribution within a certain period of time, i.e. S as _{S 1 (G X, A Y} , t M) to _{S (G X, A Y,} t N-1) of A mode in which S (G _X , A _Y , t _N ) is selected as the average value as S ₂ can be considered. Here, t _M is an arbitrary time from t ₁ to t _N-2 .

FIG. 12 is a flowchart for explaining a main part of another example of the suspicious mobile object detection control by the DSP 16 of the RFID tag communication apparatus 12 and is repeatedly executed at a predetermined cycle. In the control shown in FIG. 12, the same steps as the control shown in FIG. 11 described above are denoted by the same reference numerals, and the description thereof is omitted. In this control, after the process of S1 described above, in S15, the antenna output, that is, the intensity P _{Z of the} transmission signal transmitted from the array antenna 24 is set to the initial value P _1, and then the process of S2 and subsequent steps is performed. Executed. If the determination in S6 described above is affirmed, in S16, the intensity P _{Z of the} transmission signal is set to P _{Z + 1} . Next, in S17, the intensity P _Z of the transmission signal at that time whether the predetermined value P _max is determined. When the determination at S17 is negative, the above-described processing after S2 is executed, but when the determination at S17 is positive, the above-described processing at S7 and below is executed. The reception intensity distribution S in the control of FIG. 12 is a function of the transmission signal intensity P _Z , time t _N , directivity angle A _Y , and tag G _X. In the above processing, S15 and S16 correspond to the operation of the carrier strength control unit 50.

FIG. 13 is a flowchart for explaining a main part of still another example of the suspicious moving object detection control by the DSP 16 of the RFID tag communication apparatus 12 and is repeatedly executed at a predetermined cycle. In the control shown in FIG. 13, the same steps as those shown in FIGS. 11 and 12 described above are denoted by the same reference numerals, and the description thereof is omitted. In this control, following the processing of S15 described above, in S18, the reader R _i, that is, the wireless tag communication device 12 in the predetermined wireless tag communication device 12 identified by the symbol R _i among the plurality of wireless tag communication devices 12 is connected. The directivity angle A _Y of the communication between them is set to A ₁ which is an initial value. Next, in S <b> 19, communication with the wireless tag 14 is performed by the readers R _{1 to} R _i, that is, a plurality of wireless tag communication devices 12, and information stored in the wireless tag 14 is read. Here, it is preferable that the readers R _{1 to} R _i perform communication with the wireless tags 14 in order so that communication batting does not occur. Then, step S20 corresponds to the operation of the received signal strength detector 64, the reader R ₁ to R _i signal of the received signal corresponding to the reply signals from a plurality of RFID tags 14 (tag G ₁ ~G _X) in each After the intensity is detected and associated with the directivity angle A _Y and stored in the storage unit 70, the above-described processing of S5 and subsequent steps is executed. Moreover, following the processing of S9 described above, in S21, the reader receives the intensity distribution at two different times t _N with respect to _{R i S 1i (G X,} A Yi, P Z) and _{S 2i (G X, A Yi} , After P _Z ) is selected, the processing from S11 onward is executed.

  Thus, according to the present embodiment, the directivity control unit 54 (S2 and S5) that controls the directivity of communication with the wireless tag 14 and each directivity defined by the directivity control unit 54 And a communication state change detection unit 66 (S9 to S11) for detecting a change in communication state within a predetermined area based on a return signal from the wireless tag 14 in By observing the inhibition of communication with the wireless tag 14 due to the movement of the mobile body 94 as a radio wave reflector, the formation of multipaths, etc., the mobile body 94 can be easily moved within a predetermined region, that is, the chamber 90. Can be detected. That is, it is possible to provide the wireless tag communication device 12 that realizes a practical security system with a simple configuration.

  In addition, a reception signal strength detection unit 64 (S4 and S20) that detects a signal strength of a reception signal received by the array antenna 24 as a reception antenna is provided, and the communication state change detection unit 66 detects the received signal strength. Since the change in the communication state in the chamber 90 is detected based on the signal strength of the received signal detected by the unit 64, the change in the communication state in the target region is detected in a practical manner. Can do.

  The communication state change detection unit 66 detects a change in the communication state in the chamber 90 based on the average value of the signal strength of the reception signal detected by the reception signal strength detection unit 64. By comparing with the average value of the signal strength of the received signal, the detection variation of the received signal strength and the fluctuation of the received signal strength due to the steady environmental change in the chamber 90 can be absorbed, and within the target region in a practical manner. It is possible to detect a change in the communication state in.

  The communication state change detecting unit 66 compares the signal strength of the received signal detected by the received signal strength detecting unit 64 with the signal strength of the received signal detected last time by the received signal strength detecting unit 64. By detecting the change of the communication state in the chamber 90, the change of the communication state in the target region is detected in a practical manner by comparing with the signal strength of the previous reception signal. Can do.

  In addition, a carrier strength control unit 50 (S15 and S16) for controlling the strength of the carrier wave of the transmission signal is provided, and the communication state change detection unit 66 responds to each carrier whose strength is changed by the carrier strength control unit 50. Since the change of the communication state in the chamber 90 is detected by comparing the return signal returned from the wireless tag 14, the comparison is made by comparing the received signals corresponding to the transmitted signals having different intensities. It is possible to improve the resolution for detecting the change in the communication state in the region.

  The wireless tag communication device 12 communicates information with the plurality of wireless tags 14, and the communication state change detection unit 66 is based on return signals from the plurality of wireless tags 14. Since the change in the communication state in the chamber 90 is detected, the area to be detected can be expanded by increasing the number of wireless tags 14 that perform communication.

  Further, an array antenna 24 having a plurality of antenna elements 22 functioning as a transmission antenna and a reception antenna is provided, and the directivity control unit 54 selects at least one of the transmission directivity of the transmission signal and the reception directivity of the reception signal. Since it is to be controlled, it is possible to control the directivity of communication with the wireless tag 14 in a practical manner, and the target area based on the return signal from the wireless tag 14 in each directivity It is possible to detect a change in the communication state within the network.

  Further, since the mobile body 94 is detected to enter the chamber 90 based on the change in the communication state detected by the communication state change detection unit 66, a suspicious person or the like in the target area is detected. A security system that detects the intrusion of a moving object can be realized.

  Further, since the movement of the moving body 94 in the chamber 90 is detected based on the change in the communication state detected by the communication state change detection unit 66, a moving object such as a suspicious person in the target area. It is possible to realize a security system that detects movement of the user.

  Further, by using the wireless tag communication device 12 to communicate information with a predetermined region, that is, the wireless tag 14 disposed in the chamber 90, a change in the communication state in the chamber 90 is detected. The wireless tag communication system 10 observes inhibition of communication with the wireless tag 14 due to movement of the moving body 94 as a radio wave shield or radio wave reflector, formation of a multipath, etc. The movement of the moving body 94 can be easily detected. That is, the wireless tag communication system 10 that realizes a practical security system with a simple configuration can be provided.

  In addition, since the plurality of RFID tag communication devices 12 are provided, and the plurality of RFID tag communication devices 12 detect changes in the communication state in the chamber 90, the plurality of RFID tag communication devices 12 are used to The movement of the moving body 94 in the chamber 90 can be detected more suitably.

  Further, since the plurality of wireless tag communication devices 12 alternately communicate information with the wireless tag 14, communication with the predetermined wireless tag 14 by the plurality of wireless tag communication devices 12 is performed. Can be suitably prevented.

  In addition, since the plurality of wireless tags 14 are fixed in the chamber 90, the received signals corresponding to the plurality of wireless tags 14 whose relative positions with respect to the chamber 90 are fixed are compared. By doing so, it is possible to detect a change in the communication state in the room 90 in a practical manner.

  In addition, since the plurality of wireless tags 14 are provided in different directions with respect to the wireless tag communication device 12, the relative directions with respect to the wireless tag communication device 12 are fixed to the plurality of wireless tags 14. By comparing the corresponding received signals, a change in the communication state in the chamber 90 can be detected in a practical manner.

  The preferred embodiments of the present invention have been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and may be implemented in other modes.

  For example, in the above-described embodiment, the RFID tag communication apparatus 12 controls the transmission directivity of the transmission signal and the reception directivity of the reception signal by the directivity control unit 54. However, the present invention is not limited to this, as long as it controls at least one of the transmission directivity of the transmission signal and the reception directivity of the reception signal, and may not necessarily be able to control both.

  In the above-described embodiment, the DSP 16 has all the control functions such as the carrier strength control unit 50, the directivity control unit 54, the received signal strength detection unit 64, and the communication state change detection unit 66. However, some or all of the control functions may be provided as individual control devices. The control by these control functions may be digital signal processing or analog signal processing.

  In the above-described embodiment, the plurality of wireless tag communication devices 12 provided in the chamber 90 alternately communicate information with the wireless tag 14. As long as communication batting can be prevented by appropriately controlling the communication directivity in the communication device 12, the communication may not necessarily be performed alternately, and the plurality of RFID tag communication devices 12 may transmit signals in synchronization. May be used.

  In addition, although not particularly mentioned in the above-described embodiment, a configuration and an alarm for capturing and displaying an image in the chamber 90 when the suspicious moving body detecting unit 68 detects the suspicious moving body 94 are provided. It goes without saying that a configuration for sounding or a configuration for reporting to a security company via a predetermined line may be provided.

  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 which is one Example of this 2nd invention. It is a figure explaining the structure of the wireless tag communication apparatus which is one Example of this 1st invention. FIG. 2 is a diagram illustrating a configuration of a wireless tag circuit element provided in the wireless tag of FIG. 1. It is a figure explaining the security system using the radio | wireless tag communication system of FIG. 5 is a graph showing a signal intensity distribution of a received signal corresponding to each directivity direction when the communication directivity is changed in the RFID tag communication apparatus provided in the RFID tag communication system of FIG. 4. It is a figure explaining another example of the security system using the radio | wireless tag communication system of FIG. 7 is a table illustrating recognition results of a plurality of wireless tags by a wireless tag communication device provided in the wireless tag communication system of FIG. 6. It is a figure explaining another example of the security system using the radio | wireless tag communication system of FIG. It is a figure explaining another example of the security system using the radio | wireless tag communication system of FIG. It is a figure explaining another example of the security system using the radio | wireless tag communication system of FIG. 3 is a flowchart for explaining a main part of an example of suspicious mobile object detection control by a DSP of the RFID tag communication apparatus of FIG. 2. It is a flowchart explaining the principal part of another example of the suspicious mobile body detection control by DSP of the RFID tag communication apparatus of FIG. 6 is a flowchart for explaining a main part of still another example of suspicious mobile object detection control by a DSP of the RFID tag communication apparatus of FIG.

Explanation of symbols

10: wireless tag communication system 12: wireless tag communication device 14: wireless tag 22: antenna element 24: array antenna (transmitting antenna, receiving antenna)
50: Carrier strength control unit 54: Directivity control unit 64: Received signal strength detection unit 66: Communication state change detection unit 90: Room (region)
94: Mobile object

Claims (14)

A transmission signal is transmitted from the transmission antenna toward the wireless tag, and information is communicated with the wireless tag by receiving a return signal returned from the wireless tag according to the transmission signal by the reception antenna. A wireless tag communication device,
A directivity control unit that controls the directivity of communication with the wireless tag;
A communication state change detecting unit that detects a change in communication state within a predetermined area based on a return signal from the wireless tag in each directivity determined by the directivity control unit. A wireless tag communication device.   A reception signal strength detection unit configured to detect a signal strength of a reception signal received by the reception antenna, wherein the communication state change detection unit is configured based on the signal strength of the reception signal detected by the reception signal strength detection unit; The wireless tag communication device according to claim 1, which detects a change in a communication state within a region.   The RFID tag communication according to claim 2, wherein the communication state change detection unit detects a change in communication state in the region based on an average value of signal strengths of reception signals detected by the reception signal strength detection unit. apparatus.   The communication state change detection unit compares the signal strength of the reception signal detected by the reception signal strength detection unit with the signal strength of the reception signal previously detected by the reception signal strength detection unit, thereby comparing the region. The wireless tag communication device according to claim 2, wherein a change in a communication state is detected.   A carrier signal strength control unit that controls the carrier strength of the transmission signal, and the communication state change detection unit returns a reply signal returned from the wireless tag according to each carrier whose strength is changed by the carrier strength control unit The RFID tag communication apparatus according to claim 1, wherein a change in a communication state in the area is detected by comparing the two.   The wireless tag communication device communicates information with a plurality of the wireless tags, and the communication state change detection unit performs communication within the region based on return signals from the plurality of wireless tags. The wireless tag communication device according to claim 1, which detects a change in state.   At least one of the transmission antenna and the reception antenna is an array antenna having a plurality of antenna elements, and the directivity control unit controls at least one of the transmission directivity of the transmission signal and the reception directivity of the reception signal. The wireless tag communication device according to any one of claims 1 to 6.   The RFID tag communication apparatus according to any one of claims 1 to 7, wherein an intrusion of a moving body into the area is detected based on a change in communication state detected by the communication state change detection unit.   The RFID tag communication apparatus according to any one of claims 1 to 7, wherein movement of a moving body in the region is detected based on a change in communication state detected by the communication state change detection unit.   Detecting a change in a communication state in an area by communicating information with the RFID tag disposed in the predetermined area using the RFID tag communication apparatus according to claim 1. A wireless tag communication system.   The RFID tag communication system according to claim 10, comprising a plurality of the RFID tag communication devices, and detecting a change in a communication state in the region by the plurality of RFID tag communication devices.   The wireless tag communication system according to claim 11, wherein the plurality of wireless tag communication devices alternately communicate information with the wireless tag.   The wireless tag communication system according to claim 10, wherein a plurality of the wireless tags are provided in a fixed position in the area.   The wireless tag communication system according to claim 13, wherein the plurality of wireless tags are provided in different directions with respect to the wireless tag communication device.

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