JP2004289765A - Frequency changeover type rfid device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RFID device for receiving multiple pieces of ID data concerning the RFID device for receiving ID data which are transmitted from a plurality of ID tags. <P>SOLUTION: The oscillation frequency of a signal intermittently transmitted from each ID tag is changed-over whenever transmission is performed. Thus, multiple pieces of ID data are simultaneously received. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
[0001] 1. Field of the Invention [0002] The present invention relates to an RFID device that manages information on a moving body by detecting that a large number of moving objects or people approach or pass.
[0002]
2. Description of the Related Art In a conventional method, an oscillation frequency when transmitting ID number data from an ID tag is fixed, and a plurality of ID tags can be received by an intermittent transmission method.
For example, Japanese Patent Application No. Hei 6-222698 and Japanese Patent Application No. 2002-146959.
[0003]
According to the above prior art, the frequency of oscillation from the ID tag is fixed, and the number of ID tags that can be received simultaneously is limited.
[0004] Also, if there is a large noise around the oscillation frequency, the reception may be interrupted and the ID code may not be received.
[0005]
In order to solve the above-mentioned problems, an invention according to claim 1 is an RFID device which switches a transmission frequency every time an ID tag intermittently oscillates.
ID data and the like are transmitted from a tag using a PLL or a DDS oscillator or the like that oscillates an arbitrary frequency at a high frequency (several tens to several hundreds of MHz) that can be frequency-controlled by microcomputer software.
[0007]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described based on embodiments with reference to the drawings.
[0008]
FIG. 1 shows the configuration of the RFID device.
A low-frequency trigger transmission radio wave generated by the trigger transmission circuit 21 of the ID receiver 2 is transmitted from the trigger transmission antenna 22 to the surroundings.
As the trigger transmission frequency, a low frequency around 10 to 500 kHz is suitable.
The ID tag 1 has a trigger receiving antenna 11, and when a trigger signal is received, the trigger signal is detected by the trigger receiving circuit 12, and the microcomputer 13 operates.
The PLL circuit 14 generates a high frequency according to the stability of the crystal unit 15.
Each time intermittent transmission is performed, an arbitrary frequency is set from the microcomputer, and the PLL circuit oscillates at a different frequency.
The oscillation frequency of the PLL circuit 14 is selected every time one of 311 MHz, 312 MHz, and 313 MHz is transmitted, and is set by the microcomputer. The microcomputer 13 outputs the ID code of the tag-specific number to the PLL circuit 14, modulates the oscillation frequency, and transmits the ID data.
The signal transmitted from the ID tag enters the antenna 23 of the ID receiver 2 and is received by the ID receiving circuit 24.
The transmission time of the ID data becomes 1 mS when transmitted at a speed of 64 KBPS in a 64-bit configuration, for example.
Therefore, if intermittent transmission is performed after transmitting for 1 mS and pausing for 9 mS, it is possible to receive a maximum of 10 ID tag data at one frequency.
The ID receiving circuit 24 has a receiving circuit for each frequency so as to simultaneously receive each frequency transmitted by the ID tag.
When three frequencies are simultaneously received, up to 30 ID tag signals can be received under the intermittent transmission condition.
The order of the frequency transmitted by the ID tag may be a predetermined order, but it is effective to make the order random.
Even if the ID tags simultaneously transmitting at the same frequency interfere with each other and cannot be received at the same time, if the next intermittently transmitting frequency is different, they can be received.
[0014]
The received ID data is displayed or recorded by the computer 25 together with time information and the like, and performs information processing required by the user.
The contents of the information processing are, for example, software processing such as displaying that the ID tag has approached the receiver, and storing and displaying the passing time and the number of passing times.
[0015]
As described above, according to the present invention, the number of tags that can be received simultaneously increases in proportion to the number of switching of the oscillation frequency by switching the oscillation frequency transmitted from the ID tag each time intermittent transmission is performed. As a result, even if a large noise is disturbed at a specific frequency, the signal can be received at another oscillation frequency that can be switched every moment, and a highly reliable RFID device can be provided.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the RFID device of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 ID tag 11 trigger receiving antenna 12 trigger receiving circuit 13 microcomputer 14 PLL circuit 15 crystal oscillator 16 antenna 17 charging circuit 18 rechargeable battery 2 ID receiver 21 trigger transmitting circuit 22 trigger transmitting antenna 23 ID receiving antenna 24 ID receiving circuit 25 computer

Claims (1)

In an RFID device that reads an ID code from a plurality of ID tags, a trigger radio wave is transmitted from a receiver at a low frequency. The RFID device according to claim 1, wherein in the intermittent transmission operation, the oscillation frequency is switched and the transmission is performed, and the receiver receives the transmission frequencies switched and transmitted simultaneously.

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