JP2006211165A - Communication method of rfid tag and read-write machine used therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication method of an RFID tag capable of quickly processing a plurality of RFID tags, and to provide a read-write machine for the RFID tag used for the method. <P>SOLUTION: In the communication method of the RFID tag, a frequency range having prescribed width with a prescribed communication frequency as the center is divided into a plurality of frequency bands (3a, 3b, 3c), and each of the plurality of frequency bands (3a, 3b, 3c) is used for the communication 4 between the read-write machine 1 and one RFID tag (2a, 2b, or 2c). The read-write machine for the RFID tag used for the communication method simultaneously processes signals at a plurality of frequency bands, and superposes the signals for transmission and reception. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an RFID tag communication method and a reader / writer used for the method.

  In recent years, an information management method for exchanging information by wireless communication with a recording medium having predetermined information has rapidly spread. A rail freight collection system using an IC card is well known as one that uses this type of information management technique. On the other hand, RFID tag (micro wireless IC chip) technology is a product that replaces barcodes. It is being researched as a technology for identification and management, or as a basic technology for promoting socialization and automation of society.

When this RFID tag is used for product identification or the like, it is necessary to recognize a plurality of tags at the same time. As a technique for communicating with a plurality of wireless cards, for example, those disclosed in the following documents have been proposed.
Japanese Patent Publication No. 3-2271 JP 2000-69028 A JP 2000-155813 A

  However, all of the techniques disclosed in the above documents are provided with time slots, a plurality of wireless cards existing in a communicable area are assigned to each time slot, and communication processing is sequentially performed according to the order of the time slots. . For this reason, while the communication process for one wireless card is being performed, the communication process for the other wireless card is not performed, and there is a problem that the processing time until the communication with all the wireless cards is completed becomes long.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an RFID tag communication method capable of processing a plurality of RFID tags in a short time and an RFID tag reader / writer used for the method.

  The RFID tag communication method according to the present invention divides a frequency range having a predetermined width centered on a predetermined communication frequency into a plurality of frequency bands, and each of the plurality of frequency bands is divided into a reader / writer and one RFID tag. It is used for communication with.

  The RFID tag reader / writer according to the present invention is characterized by simultaneously processing signals in a plurality of frequency bands.

  The RFID tag reader / writer according to the present invention may transmit and receive the signals superimposed on each other.

  According to the RFID tag communication method of the present invention, a plurality of communication channels are obtained by dividing a frequency range having a predetermined width centered on a predetermined communication frequency used as a single communication channel into a plurality of frequency bands. Can be set. Therefore, it is possible to communicate simultaneously with a plurality of RFID tags, and the processing time up to the time obtained by multiplying the processing time per RFID tag by the number of processing is calculated for each RFID tag. Can be shortened to the same length as the processing time.

  According to the RFID tag reader / writer according to the present invention, a plurality of communication channels can be handled simultaneously by simultaneously processing signals used in a plurality of communication channels having different frequency bands. Therefore, it can be suitably used for the RFID tag communication method according to the present invention.

  If signals in a plurality of frequency bands are superimposed and transmitted / received, communication with the RFID tag in each communication channel can be performed completely simultaneously. Therefore, it is possible to prevent the occurrence of a time lag between communication channels as compared with the case where each signal is transmitted and received individually.

FIG. 1 is a block diagram showing a specific example of an RFID tag communication method according to the present invention, and FIG. 2 is a flowchart of the same.
In this communication method, a frequency range of 2 MHz with a predetermined width centered on 13.56 MHz, that is, a frequency range of 12.56 MHz to 14.56 MHz is used as the predetermined communication frequency. This frequency range is divided into 200 frequency bands 3a, 3b, 3c... In increments of 10.56 MHz to 10 kHz, and each of these frequency bands 3a, 3b, 3c. Used for communication with tag 2. The plurality of frequency bands 3a, 3b, 3c,... In this specific example are, for example, 12.565 MHz ± 5 kHz, 12.575 MHz ± 5 kHz, 12.585 MHz ± 5 kHz, etc., but the step width (frequency bands 3a, 3b 3c...) Is not limited, and may be a width suitable for the communication device, communication circumstances, and the like. In FIG. 1, for convenience, only a plurality of frequency bands 3a, 3b, and 3c are shown, and the RFID tag performs communication in each of these frequency bands 3a, 3b, and 3c. Only three of these shall be shown.

  The reader / writer 1 used in this communication method is an RFID tag reader / writer according to the present invention, and the information processing unit 11 simultaneously processes signals of a plurality of frequency bands 3a, 3b, and 3c. The signals in the frequency bands 3a, 3b, and 3c are superimposed and decomposed in the modem unit 12 and transmitted / received via a transmission / reception device (not shown).

  The RFID tags 2a, 2b, and 2c have their input filters set so that the communicable frequencies are limited (only specific frequencies can be input). The RFID tag 2a receives only the frequency band 3a, 2b 3b, and 2c only 3c.

As shown in FIG. 2, the communication is performed according to the following procedure.
First, the reader / writer 1 transmits a multiple interrogation signal formed by superposing signals of the frequency bands 3a, 3b, and 3c (S1). The RFID tags 2a, 2b, and 2c that have received this multiple interrogation signal are frequency bands determined for their own communication among the plurality of frequency bands 3a, 3b, and 3c (for example, the frequency band 3a for the RFID tag 2a). ) Response signal is transmitted (S2). The reader / writer 1 that has received the response signal identifies the RFID tags 2a, 2b, and 2c (S3), and performs communication processing such as data collection and rewriting (S4). In FIG. 1, since the number of RFID tags 2a, 2b, and 2c and the number of frequency bands 3a, 3b, and 3c coincide with each other, the communication process is completed. If the number is larger than the number, all the RFID tags cannot be processed at one time, so the communication processing for the remaining RFID tags is performed (S5).

  According to this communication method, 200 communication channels can be set in a frequency range of 13.56 MHz ± 1 MHz with a predetermined width centered on a predetermined communication frequency used as a single communication channel. Therefore, it becomes possible to perform communication simultaneously with a plurality of RFID tags 2a, 2b, 2c... And the processing time up to that time, which is the length obtained by multiplying the processing time per RFID tag by the number of processing, The processing time per RFID tag can be shortened to the same length. That is, it can be reduced to a maximum of 1/200 of the conventional processing time. However, the shortening rate varies depending on the number of signals that can be superimposed. For example, if the number of signals that can be superimposed is 50, the maximum number of RFID tags that can be processed simultaneously is 50, and the reduction rate is also 1/50.

  Further, by transmitting and receiving signals in a plurality of frequency bands 3a, 3b, and 3c in an overlapping manner, communication with the RFID tags 2a, 2b, and 2c in each communication channel can be performed at the same time. Therefore, it is possible to prevent the occurrence of a time lag between communication channels as compared with the case where each signal is transmitted and received individually.

3 and 4 show another specific example of the RFID tag communication method according to the present invention. FIG. 3 is a block diagram of the communication method, and FIG. 4 is a flowchart of the communication method.
The device configuration for this communication method is basically the same as the device configuration of the communication method described above, and substantially the same parts are denoted by the same reference numerals, but have the following differences.
First, the reader / writer 1 does not have the modulation / demodulation unit 12 and performs communication by a general narrow band communication method (spread spectrum method, SSB communication method, etc.). The RFID tags 2a, 2b, and 2c select a frequency based on a value obtained by logically calculating the ID information from the reader / writer 1 and its own ID information as a communication frequency.

Communication in this communication method is performed according to the following procedure as shown in FIG.
First, the reader / writer 1 transmits a narrowband interrogation signal for each frequency band 3a, 3b, 3c (S11). The RFID tags 2a, 2b, and 2c that have received these inquiry signals select one frequency band (for example, the frequency band 3a in the case of the RFID tag 2a) from a plurality of frequency bands 3a, 3b, and 3c, and determine a communication channel. Then, a response signal in the frequency band is transmitted (S12). Upon receiving this response signal, the reader / writer 1 identifies each RFID tag 2a, 2b, 2c and starts communication for each channel using each frequency band 3a, 3b, 3c (S13), and receives and rewrites data. And the like (S14). In FIG. 4, since the RFID tags 2a, 2b, and 2c select different frequency bands 3a, 3b, and 3c, all of the communication is completed, but a plurality of RFID tags select the same frequency band. If the number of frequency bands is insufficient, all RFID tags cannot be processed at one time, and communication processing for the remaining RFID tags is performed (S15).

  According to this communication method, since the number of frequency bands is 200, the conventional processing time can be shortened to a maximum of 1/200.

  Note that the frequency for determining the communication channel with the reader / writer 1 is set to an active filter for the input circuit of the RFID tag, and the filter value is set at random (randomization is based on the value indicated by the random generator, for example) The filter value may be selected by shifting the filter value sequentially for each communication.

It is a block diagram which shows the specific example of the communication method of the RFID tag concerning this invention. FIG. It is a block diagram which shows the other specific example of the communication method of the RFID tag concerning this invention. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reader / Writer 2a, 2b, 2c RFID tag 3a, 3b, 3c Frequency band 4 Communication 11 Information processing part 12 Modulation / demodulation part

Claims (3)

  A frequency range with a predetermined width centered on a predetermined communication frequency is divided into a plurality of frequency bands (3a, 3b, 3c), and each of the plurality of frequency bands (3a, 3b, 3c) is read / written (1) And RFID tag (2a, 2b or 2c) used for communication (4), RFID tag communication method,   An RFID tag reader / writer that processes signals in a plurality of frequency bands simultaneously. The RFID tag reader / writer according to claim 2, wherein the signals are superimposed and transmitted / received.

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