RF tag reader and method

• US 20080061942A1
• Filed: 07/30/2007
• Published: 03/13/2008
• Est. Priority Date: 09/12/2006
• Status: Abandoned Application

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Maniwa, Toru
• Application Number:
  US11/882,033
• Publication Number:
  US 20080061942A1
• Time in Patent Office: Days
• US Class Current: 340/10.3
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
• 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
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00

Abstract

A disclosed RF tag reader includes a main antenna with directivity covering a first area; a sub antenna with directivity covering a second area that is smaller than the first area; and a switch control unit configured to selectively switch between the main antenna and the sub antenna. In response to receiving an answer signal via the sub antenna from a wireless communications unit moving together with one or more management objects, the switch control unit switches an antenna used for communications from the sub antenna to the main antenna and the RF tag reader performs communications, via the main antenna, with an RF tag each accompanying one of the management objects.

Claims

1. An RF tag reader comprising:

a main antenna with directivity covering a first area;

a sub antenna with directivity covering a second area that is smaller than the first area; and

a switch control unit configured to selectively switch between the main antenna and the sub antenna;

wherein;

in response to receiving an answer signal via the sub antenna from a wireless communications unit moving together with one or more management objects, the switch control unit switches an antenna used for communications from the sub antenna to the main antenna and the RF tag reader performs communications, via the main antenna, with an RF tag each accompanying one of the management objects.

2. The RF tag reader according to claim 1, wherein the sub antenna has a lower antenna gain than that of the main antenna.

3. The RF tag reader according to claim 2, wherein the main antenna comprises a planar patch antenna and the sub antenna comprises a dipole antenna.

4. The RF tag reader according to claim 2, wherein the sub antenna comprises an attenuator configured to reduce its antenna gain.

5. The RF tag reader according to claim 2, wherein each of the main antenna and the sub antenna comprises a mechanism configured to adjust its antenna gain.

6. The RF tag reader according to claim 1, wherein the wireless communications unit corresponds to one of plural of the RF tags accompanying the one or more management objects.

7. The RF tag reader according to claim 1, wherein the wireless communications unit comprises another RF tag that does not correspond to any of plural of the RF tags accompanying the one or more management objects.

8. The RF tag reader according to claim 7, wherein the wireless communications unit is attached to a carrying unit configured to carry the one or more management objects.

9. The RF tag reader according to claim 7, wherein the main antenna and the sub antenna use electric waves of different polarization properties.

10. The RF tag reader according to claim 9, wherein linearly polarized waves having different polarization planes are used as the electric waves of different polarization properties.

11. The RF tag reader according to claim 9, wherein circularly polarized waves having different rotational directions are used as the electric waves of different polarization properties.

12. The RF tag reader according to claim 1, wherein the sub antenna comprises an array antenna comprising plural antenna elements.

13. A method of communicating performed by an RF tag reader comprising:

a main antenna with directivity covering a first area;

a sub antenna with directivity covering a second area that is smaller than the first area; and

a switch control unit configured to selectively switch between the main antenna and the sub antenna;

the method comprising the steps of;

receiving an answer signal via the sub antenna from a wireless communications unit moving together with one or more management objects;

switching an antenna used for communications from the sub antenna to the main antenna; and

performing communications, via the main antenna, with an RF tag accompanying one of the management objects.

14. The method according to claim 13, further comprising the step of switching the antenna used for communications back to the sub antenna from the main antenna after completing performing communications with one or more of the RF tags accompanying the management objects.