RFID device detection system and method

• US 20060192002A1
• Filed: 05/01/2006
• Published: 08/31/2006
• Est. Priority Date: 04/03/2003
• Status: Active Grant

• Current Assignee: Avery Dennison Retail Information Services LLC (Avery Dennison Corporation)
• Original Assignee: Ian J. Forster
• Inventors: Forster, Ian J.
• Granted Patent: US 7,273,173 B2
• Time in Patent Office: Days
• US Class Current: 235/385
• 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 7/10346 the antenna being of the far field type, e.g. HF types or dipoles

Abstract

An RFID device detection system includes a proximity locator, which generates an electric field for reading an antennaless RFID device, or for reading other, antennaed RFID devices. An antennaless RFID device includes non-antenna conductive leads coupled to a chip. The proximity locator includes one or more conductors forming a transmission line structure arranged to set up a strong RF electric field in proximity to the locator. The strong RF electric field may be a short- range field that provides significant RF energy only over a relatively short distance, when compared with traditional RF fields that are set up over a relatively large distance. The short-range RF field allows coupling to antennaed and antennaless RFID devices that are near to the proximity locator. The RFID device detection system may be employed in a variety of tasks, including inventory control and theft detection.

Claims

1. A method of detecting RFID devices, comprising:

producing an RF electric field about a transmission line structure by sending an AC signal along at least two transmission lines of the transmission line structure;

powering the RFID devices using the RF electric field; and

detecting the RFID devices using a reader mechanically coupled to the transmission line structure.

2. The method of claim 1, wherein the transmission lines are substantially parallel to one another, with a gap therebetween.

3. The method of claim 1, wherein the RFID devices include antennaless RFID devices.

4. The method of claim 3, wherein the powering the RFID devices and the detecting the RFID devices include powering and detecting while the RFID devices are at least partially within a gap between the transmission lines.

5. The method of claim 4, wherein the transmission lines are substantially parallel to one another.

6. The method of claim 1, wherein the powering includes capacitively coupling the transmission line structure and the RFID devices.

7. The method of claim 1, wherein the powering includes magnetically coupling the transmission line structure and the RFID devices.

8. The method of claim 1, wherein the RFID devices include antennaed RFID devices.

9. A method of tracking objects, comprising:

placing respective RFID devices on each of the objects; and

electrically detecting when the objects are moved away from a proximity locator that is part of an RFID device detection system;

wherein the electrically detecting includes detecting the RFID devices using short-range coupling.

10. The method of claim 9, wherein the RFID devices include antennaless RFID devices.

11. The method of claim 9, wherein the RFID device include antennaed RFID devices.

12. The method of claim 9, wherein the detecting includes detecting changes in a short-range RF electric field produced by the proximity locator.

13. The method of claim 9, further comprising sending an alert when a predetermined situation is uncovered by the detecting.

14. The method of claim 13, wherein the predetermined situation is removal of more than a predetermined number of objects over a predetermined time interval.

15. The method of claim 13, wherein the predetermined situation is removal of the objects out of a predetermined order.

16. The method of claim 15, wherein the predetermined situation is the removal of an object that is other than a topmost or forwardmost object.

17. The method of claim 15, wherein the RFID devices have substantially unique individual signatures such that the objects are separately identifiable by the proximity locator.

18. The method of claim 17, further comprising, in the RFID device detection system, storing information regarding order of the objects.

19. The method of claim 9, wherein the RFID devices have substantially unique individual signatures such that the objects are separately identifiable by the proximity locator.

20. The method of claim 9, wherein the proximity detector includes a pair of transmission lines configured to produce a short-range RF electric field between the transmission lines.