Position locator for locating position of radio tag

• US 20070126583A1
• Filed: 03/29/2006
• Published: 06/07/2007
• Est. Priority Date: 12/06/2005
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Maniwa, Toru, Kimura, Shigekazu
• Application Number:
  US11/391,231
• Publication Number:
  US 20070126583A1
• Time in Patent Office: Days
• US Class Current: 340/572.200
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 3/38 using adjustment of real or effective orientation of directivity characteristic of an antenna or an antenna system to give a desired condition of signal derived from that antenna or antenna system, e.g. to give a maximum or minimum signal G01S3/16, G01S3/28 take precedence
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/10128 the step consisting of detection of the presence of one or more record carriers in the vicinity of the interrogation device

Abstract

An antenna having directivity receives a harmonic signal generated from a radio tag, and position information corresponding to a direction and reception information indicating whether or not a harmonic signal was received from the direction are output, regarding each of the directions to which the antenna is directed.

Claims

1. A position locator for locating a position of a radio tag in which data can be read and written in a contactless manner, comprising:

an antenna device having a directionality, for receiving a harmonic signal generated from the radio tag;

a control device for controlling a direction to which the antenna device is directed; and

an outputting device for outputting position information corresponding to a direction, and reception information indicating whether or not the harmonic wave from the direction was received, regarding each of the directions to which the antenna device is directed.

2. The position locator according to claim 1, further comprising:

a rotation control device for causing the antenna device to rotate about a rotation axis in accordance with a control signal from the control device, wherein;

the antenna device includes a plurality of antenna elements arrayed at a prescribed interval.

3. The position locator according to claim 1, further comprising:

a conversion device for converting a control signal from the control device into a phase control signal, wherein;

the antenna device includes a plurality of antenna elements arrayed at a prescribed interval and a plurality of variable phase shifters for varying phases of signals output from the respective antenna elements in accordance with the phase control signal.

4. A radio tag, comprising:

a receiving device for receiving an unmodulated continuous wave as an interrogation signal from a reader/writer;

a harmonic wave generation device for generating a harmonic signal from the received continuous wave; and

a transmitting device for transmitting a response signal corresponding to the interrogation signal and the harmonic signal.

5. The radio tag according to claim 4, wherein:

the harmonic wave generation device includes a non-linear element, and includes a rectifier device for generating a power voltage from the received continuous wave.

6. The radio tag according to claim 5, wherein:

the rectifier device includes two diodes having a threshold value voltage which is equal to or higher than a prescribed value, as the non-linear elements.

7. The radio tag according to claim 6, wherein:

the threshold value voltage is equal to or higher than 2.5% of voltage amplitude of the received continuous wave.

8. The radio tag according to claim 5, wherein:

the rectifier device includes two diodes which are different from each other in size, as the non-linear elements.

9. The radio tag according to claim 8, wherein:

a size of one of the two diodes is equal to or smaller than 89.5% of the other one.

10. The radio tag according to claim 4, wherein:

the harmonic wave generation device includes a non-linear element, and includes a variable load device for generating the response signal.

11. A radio tag, comprising:

a receiving device for receiving an unmodulated continuous wave as an interrogation signal from a reader/writer;

a light emitting device for generating light from the received continuous wave; and

a transmitting device for transmitting a response signal corresponding to the interrogation signal.

12. The radio tag according to claim 11, wherein:

the light emitting device includes a light emitting element, and includes a rectifier device for generating a power voltage from the received continuous wave.

13. The radio tag according to claim 11, wherein:

the light emitting device includes a light emitting element, and includes a variable load device for generating the response signal.