JP2008131221A - Moving body identification device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a moving body identification device which can acquire an effect of the magnification of an adaptation range by a simple configuration without newly preparing an antenna changeover switch, and a control function and control software for the switch in preparing a plurality of antennas in order to expand the adaptation range for a communication range and an arrangement method of an IC tag. <P>SOLUTION: A reader writer 20 has a transmission unit 2 and a receiving unit 7 which constitute a tranceiving unit to tranceive a radio signal, an antenna 5, an antenna 6, and a divider 40 which is inserted between the antennas 5 and 6 and the tranceiving unit. The reader writer has a circulator 3 which divides and combines transmission and reception, and the circulator 3 is connected to the divider 40. A hopping control unit 13 which controls a frequency of a radio carrier wave is installed in a control unit 1 to perform radio communication using a frequency hopping communication system with the IC tags. The antenna 5 or 6 is selected by the divider 40 according to the carrier wave frequency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mobile unit identification apparatus that performs wireless communication with a responder including a mobile information communication unit such as an IC tag, and more particularly to a mobile unit identification apparatus that performs radio communication using a frequency hopping communication method.

  A mobile object identification device using wireless communication between an IC tag (responder) having an IC chip and an antenna and a reader / writer (interrogator) and a system using the same are practically used in various fields such as distribution, transportation, and medical care. It has become difficult.

  Since such a system using an IC tag has various usage forms, different specifications are required for each purpose. For example, when an IC tag is attached to a product to be transported on a belt conveyor and data is written to or read from the IC tag using a reader / writer antenna fixed to the belt conveyor side, In order to avoid reading errors due to orientation and position, a plurality of antennas are installed in the reader / writer to cover a decrease in the communication function between the reader / writer and the IC tag depending on the orientation and position of the IC tag.

  As described above, in a reader / writer having a plurality of antennas, it is necessary to switch the antenna by a switch according to the direction and position of the IC tag. However, many proposals have been made for a reader / writer having a method of switching this antenna by a switch. .

  As a typical example of a reader / writer that has a plurality of antennas and switches them with a selection switch, there is a configuration described in Patent Document 1. As an antenna switching method, in order to select an antenna that can obtain the maximum reception level, the reception level is detected while switching each antenna before data communication, and the antenna that has obtained the maximum reception level is selected by a signal from the antenna controller. In addition, a method is shown in which a threshold is set for the reception level, and switching to another antenna is performed when the reception level is equal to or lower than the predetermined threshold. In this method, in addition to the switch for switching the antenna, additional functions such as a reception level detector, a detection level / threshold storage unit, a means for comparing these levels, and a switch switching timing control unit are required.

  On the other hand, there are cases where the use of a frequency hopping method is obligated in the RFID system, which is a method of switching and using a frequency channel of a carrier wave in a wide frequency band at a certain time while following a certain rule. This method has an advantage that even if interference (narrowband interference) occurs in a specific frequency channel, narrowband interference can be avoided by switching to another frequency channel.

  FIG. 4 is a block configuration diagram of an example of an IC tag that is a reader / writer and a responder of a mobile unit identification apparatus that performs wireless communication using a frequency hopping communication method using a conventional antenna switching method. In FIG. 4, a reader / writer 21 includes a transmitter 2 and a receiver 7 for transmitting and receiving radio signals, a circulator 3 for controlling transmission and reception separately, an antenna 5 and an antenna 6 connected to the circulator 3, and an antenna changeover switch 4 for switching between them. A control unit 1 that controls generation of radio signals and antenna switching, and a reception level detection unit 8 that detects a reception level. The control unit 1 stores a reception level storage unit 9 that stores and compares the reception levels of the antennas. And a reception level comparison unit 10, a switch control unit 11 and a timing control unit 12 for controlling the antenna changeover switch 4 based on the reception level comparison unit 10, and a hopping control unit 13 for controlling the radio carrier frequency. On the other hand, the IC tag 22 includes a storage unit 16 in which information is recorded, a modulation / demodulation unit 15 that demodulates reception data and modulates transmission data, and an antenna 14.

  The transmission unit 2 of the reader / writer 21 modulates the carrier wave of the frequency determined and transmitted by the hopping control unit 13 with the inquiry data received from the control unit 1 and outputs it as a transmission signal.

  The transmission signal passes through the circulator 3 and is output by selecting the antenna 5 or the antenna 6 by the antenna changeover switch 4 and is radiated to the IC tag 22 as a question radio wave carrying the question data. This interrogation radio wave is received by the antenna 14 of the IC tag 22, demodulated by the modem 15, and then subjected to processing such as data reading and writing in the storage unit 16 according to the interrogation data. And transmitted as response radio waves with response data.

  The response radio wave transmitted from the IC tag 22 is received by the reader / writer 21 at the antenna 5 or the antenna 6 selected by the antenna changeover switch 4, and this received signal passes through the circulator 3 and is demodulated by the receiver 7 to be controlled. The received data is sent to unit 1. The reception level detection unit 8 connected to the reception unit 7 detects the reception level of the reception signal, temporarily stores it in the storage unit 9, and at the same time, determines the threshold of the reception level to be switched in advance and the current level. The reception level comparison unit 10 compares the received reception level to determine whether it is necessary to switch the antenna. When it is necessary to switch, a switching signal is sent from the switch control unit 11 to the antenna switching switch 4. Switch the antenna.

  Further, when it is necessary to select an antenna having the maximum reception sensitivity before performing communication between the reader / writer 21 and the IC tag 22 with the above configuration, details such as use of a preamble signal for obtaining transmission / reception synchronization are provided. It is necessary to introduce a control algorithm and a switching algorithm considering the communication protocol.

  In the above conventional example, the antenna changeover switch is controlled depending on the received signal level, so the circuit becomes very complicated. However, it does not depend on the received signal level, and all antennas are switched within a certain time at an arbitrary timing. In some cases, the antenna switching algorithm is simplified by covering the reading area.

JP-A-5-75506

  In the conventional method, as described above, when the antenna is switched depending on the reception level, means for monitoring and comparing the reception level is necessary for the antenna switching operation, and the antenna switching is performed without monitoring the reception level. Even in a moving body identification apparatus that performs an operation, means for sending a switching control signal while measuring the timing of frequency hopping and antenna switching is necessary, and an increase in hardware and software costs is inevitable.

  Therefore, the object of the present invention is to provide a new antenna changeover switch and a control function and control software related to this when a plurality of antennas are used in order to expand the adaptive range for the communication range and IC tag placement method. The object of the present invention is to provide a mobile object identification device that can achieve the effect of expanding the above range with a simple configuration.

  In order to achieve the above object, a mobile object identification device according to the present invention includes an interrogator that performs radio communication with a responder using a frequency hopping communication method, wherein the interrogator transmits a radio signal. A transmission / reception unit for transmitting / receiving, a plurality of antennas, and a duplexer inserted between the plurality of antennas and the transmission / reception unit, and the transmission / reception unit according to the frequency of the radio signal by the duplexer The antenna connected to is switched.

  The present invention relates to an interrogator having a plurality of antennas that perform radio communication with a responder using a frequency hopping communication method, and demultiplexes all frequency bands for frequency hopping into frequency bands corresponding to the number of antennas. The above-mentioned problems have been solved by providing a waver and operating different antennas according to the demultiplexed frequency bands. That is, the transmission signal of the interrogator is selected by the antenna that is electrically connected by the duplexer according to its frequency, and the interrogation radio wave is radiated, and the received signal received from the antenna is electrically connected to the receiving unit by the frequency The antenna to be selected is selected.

  As described above, in the mobile unit identification device of the present invention, when a plurality of antennas are used in order to expand the adaptive range for the communication range and the IC tag arrangement method, the antenna changeover switch and the control function and control software related thereto are provided. There is no need to prepare a new one, and the effect of expanding the above range can be obtained with a simple configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of a reader / writer (interrogator) of a mobile unit identification apparatus according to the present invention. In FIG. 1, a reader / writer 20 includes a transmission unit 2 and a reception unit 7 that constitute a transmission / reception unit for transmitting and receiving a radio signal, an antenna 5, an antenna 6, and a demultiplexing inserted between the antennas 5 and 6 and the transmission / reception unit. And 40.

  Further, similarly to a conventional reader / writer, it has a circulator 3 that controls transmission and reception separately, and the circulator 3 is connected to a duplexer 40. The controller 1 is provided with a hopping controller 13 that controls the radio carrier frequency. The reader / writer 20 also performs wireless communication with the IC tag 22 shown in FIG. 4 using a frequency hopping communication method.

  An example of the characteristics of the duplexer 40 of the reader / writer 20 is shown in FIG. The vertical axis indicates the attenuation, and the horizontal axis indicates the frequency. The duplexer 40 demultiplexes the entire frequency band 43 for frequency hopping into two frequency bands corresponding to the antennas 5 and 6, the A band 44 and the B band 45. To do. The demultiplexing characteristic 41 indicates the attenuation characteristic between the terminal on the circulator 3 side and the terminal on the antenna 5 side, and the demultiplexing characteristic 42 indicates the attenuation characteristic between the terminal on the circulator 3 side and the terminal on the antenna 6 side. In this example, as shown in FIG. 2, the signal of the A band 44 is connected to the antenna 5 because the path on the antenna 6 side is highly attenuated, and the signal of the B band 45 is connected to the antenna 6 because the path on the antenna 5 side is highly attenuated. Will be connected.

  Therefore, the operation of the reader / writer of this embodiment of the mobile object identification device of the present invention is as follows.

  In FIG. 1, the transmitter 2 of the reader / writer 20 modulates the carrier wave of the frequency determined and transmitted by the hopping controller 13 with the inquiry data received from the controller 1 and outputs it as a transmission signal.

  The transmission signal passes through the circulator 3 and enters the duplexer 40. Here, if the carrier frequency is within the A band 44, the transmission signal is transmitted to the antenna 5, and if the carrier frequency is within the B band 45, the transmission signal is transmitted to the antenna 6 and output, and the query data is loaded. It is radiated to the IC tag as an interrogation radio wave. After this inquiry radio wave is received by the IC tag, processing such as data reading and writing is performed according to the question data, and then the response radio wave carrying response data is sent from the IC tag to the antennas 5 and 6 of the reader / writer 20. Sent.

  The response radio wave transmitted from the IC tag is incident on the duplexer 40 in the reader / writer 20. If the frequency is in the A band 44, the reception signal from the antenna 5 is received, and if the frequency is in the B band 45, the response is received from the antenna 6. The signal enters the circulator 3, is demodulated by the receiving unit 7, and the received data is sent to the control unit 1 for processing.

  As described above, communication with the responder using the antenna 5 or the antenna 6 depends on the carrier frequency used for communication at that time, and the carrier frequency is the A band 44 (f1 to f1) as shown in FIG. Communication between the antenna 5 and the B band 45 (f2 to f3) is performed by the antenna 6 in the interval f2).

  Strictly speaking, in the duplexer 40, near the boundary between the A band 44 and the B band 45 (between f2m and f2p in FIG. 2), attenuation of pass characteristics or interference of transmission / reception signals between two antennas occurs. Although it may not be sufficient, in the frequency hopping communication method, even if there is a temporary transmission / reception failure at a specific frequency, the problem is not caused because the state is avoided by switching the frequency periodically. Also, by transmitting and receiving a set of question data and response data by switching a plurality of frequencies, an antenna having an optimum communication environment between the reader / writer and the IC tag can be selected, so that a reading error is avoided.

  In the above embodiment, an example in which the number of antennas and the division frequency band of the duplexer are two has been described. However, the demultiplexer divides the duplexer into three frequency bands as shown in FIG. It is also possible to make a device, and it is also possible to demultiplex into four or more according to the number of antennas.

  In addition, the configuration of the reader / writer in the above embodiment is merely an example, and the configuration of the reader / writer is not limited. For example, a dedicated antenna for transmission and reception is used without using a circulator as a transmission / reception separation control unit. Even if a separate antenna is provided, a duplexer can be installed between the transmission antenna and the transmission unit, and between the reception antenna and the reception unit, respectively, so that a plurality of transmission antennas and reception antennas can be provided. It is also possible to install a duplexer in one of the transmission antenna and reception antenna paths and make only one of the antennas plural.

  As described above, according to the present invention, when a plurality of antennas are used in order to expand the adaptive range with respect to the communication range and the IC tag placement method, it is compared with a conventional mobile unit identification device using switch switching. In addition, it is not necessary to newly prepare an antenna changeover switch, a control function and control software related thereto, and the effect of expanding the above range can be obtained with a simple configuration.

The block block diagram which shows one Embodiment of the reader-writer (interrogator) of the mobile body identification device by this invention. The figure which shows the example of a characteristic of the duplexer used for the reader / writer of this Embodiment. The figure which shows the example of a characteristic of the splitter which demultiplexes into three frequency bands. The block block diagram of an example of the IC tag which is the reader / writer of the mobile body identification device which performs radio | wireless communication using the frequency hopping communication system using the conventional antenna switching system, and a responder.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control part 2 Transmission part 3 Circulator 4 Antenna changeover switch 5,6,14 Antenna 7 Reception part 8 Reception level detection part 9 Reception level memory | storage part 10 Reception level comparison part 11 Switch control part 12 Timing control part 13 Hopping control part 15 Modulation / demodulation Unit 16 Storage unit 20, 21 Reader / writer 22 IC tag 40 Demultiplexer 41, 42, 47 Demultiplexing characteristic 43 Full frequency band 44 A band 45 B band 46 C band

Claims (1)

  In a mobile unit identification apparatus having an interrogator that performs radio communication with a responder using a frequency hopping communication method, the interrogator transmits and receives radio signals, a plurality of antennas, and the plurality of antennas. And a duplexer inserted between the transceiver and the antenna, wherein the duplexer switches an antenna connected to the transceiver according to the frequency of the radio signal. .

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