Antenna arrangement

• US 7,642,917 B2
• Filed: 12/21/2005
• Issued: 01/05/2010
• Est. Priority Date: 12/21/2004
• Status: Active Grant

• Current Assignee: HID Textile Services SARL
• Original Assignee: Tagsys RFID Group Incorporated (Mojix Inc)
• Inventors: Tran, Tu
• Primary Examiner(s): Trieu; Van T.
• Application Number:
  US11/793,868
• Publication Number:
  US 20080088449A1
• Time in Patent Office: 1,476 Days
• Field of Search: 340/572.1, 340/572.5, 340/572.7, 340/572.9, 343/741, 343/742, 343/842, 235/385
• US Class Current: 340/572.7
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G06K 7/10435 the interrogation device being positioned close to a conveyor belt or the like on which moving record carriers are passing conveying in accordance with bodily destination marks, see B65G47/46, sorting of objects carrying identity markings, see B07C5/34
• CPC Class Codes: H01Q 21/24 Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00

Abstract

A network of antennas for contactless reading or writing of RFID tags in a detection volume, including three or four flat, independent antennas sequentially connected to a single reader by a switch, wherein planes of the antennas pass through a reading/writing/detection volume centered in the detection volume, for every pair of antennas, an intersection of their planes is included in the optimal reading/writing volume, and the antennas are arranged so that any direction in the optimal reading/writing volume forms an angle of about 45° or less with at least one of the planes of the antennas.

Claims

1. A network of antennas for contactless reading or writing of RFID tags in a detection volume, comprising three or four flat, independent antennas sequentially connected to a single reader by a switch, wherein:

planes of the antennas pass through a reading/writing/detection volume centered in the detection volume,

for every pair of antennas, an intersection of their planes is comprised in the optimal reading/writing volume, and

the antennas are arranged so that any direction in the optimal reading/writing volume forms an angle of about 45°

or less with at least one of the planes of the antennas.

2. The network according to claim 1, wherein the optimal detection volume has a similar cross-section and a surface comprised between about 10% and about 75% of that of the detection area.

3. The network according to claim 1, comprising three orthogonal antennas offset by 120°

around a longitudinal axis of a detection area.

4. The network according to claim 1, comprising three quadrilateral antennas.

5. The network according to claim 1, comprising four antennas.

6. The network according to claim 5, wherein the antennas are rectangular and a detection area is a right-angled parallelepiped and each antenna passes through the detection area from one side of an entrance end of the detection area to an opposite side of an opposite end.

7. The network according to claim 1, wherein the switch provides an interface between the reader and the antennas are controlled by the reader and make it possible to supply the antennas independently with energy.

8. The network according to claim 1, wherein it comprises, in addition, shielding against external interference and disturbances.

9. A system for detecting RFID tags placed on a detection volume comprising at least two networks of antennas according to claim 1, wherein the networks of antennas overlap and are offset in relation to one another.

10. The system according to claim 9, wherein offsets between the networks are substantially equal to the width of the volume of the optimal reading volume in a direction of the offsets.

11. The system according to claim 9, wherein the reader is capable of controlling the switch sequentially to supply the antennas one by one, network after network.

12. A method of reading/writing an RFID tag in the network according to claim 1, comprising, when a tag passes through the network, successively and for each of the antennas:

tuning the antenna,

supplying power to the antenna with a multiplexer controlled by the reader,

reading reading/writing the RFID tag,

cutting the power supply to the antenna with the multiplexer, and

deactivating tuning the antenna.

13. The method according to claim 12, wherein tuning or deactivating the tuning comprises switching with the switch the antenna of the arrangement with an associated passive circuit for activating or deactivating the tuning.

14. The method according to claim 12, further comprising a prior step of detection, by a sensor connected to the switch and to the reader, of a tag in the network.