RFID device detection system and method

• US 20040195319A1
• Filed: 04/03/2003
• Published: 10/07/2004
• Est. Priority Date: 04/03/2003
• Status: Active Grant

• Current Assignee: Avery Dennison Retail Information Services LLC (Avery Dennison Corporation)
• Original Assignee: Avery Dennison Corporation
• Inventors: Forster, Ian J.
• Granted Patent: US 7,059,518 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 radio frequency identification (RFID) device detection system, comprising:

a reader; and

a proximity locator operatively coupled to the reader;

wherein the proximity locator includes a transmission line structure that includes at least two conductors; and

wherein the conductors are configured to produce a radio frequency (RF) field between the transmission lines.

2. The RFID device detection system of claim 1, wherein the conductors are substantially parallel to one another, with a gap therebetween.

3. The RFID device detection system of claim 2, wherein the gap is an air gap.

4. The RFID device detection system of claim 2, wherein the gap has a width of from 0.1 to 50 mm.

5. The RFID device detection system of claim 1, wherein the conductors are parts of a protrusion that may be used, for hanging therefrom, objects with respective RFID devices coupled thereto.

6. The RFID device detection system of claim 5, wherein the conductors have an air gap therebetween able to receive at least part of the RFID devices therein.

7. The RFID device detection system of claim 1, wherein the conductors are mounted on a substrate of dielectric material.

8. The RFID device detection system of claim 1, wherein the conductors are at least parts of respective rods that are in turn parts of the protrusion.

9. The RFID device detection system of claim 1, wherein the proximity locator has additional transmission line structures that produce RF electric fields at additional locations.

10. The RFID device detection system of claim 9, wherein the transmission line structures are at least parts of respective protrusions.

11. The RFID device detection system of claim 1, wherein the proximity locator is part of a rack for displaying items.

12. The RFID device detection system of claim 1, in combination with an RFID device that is operatively coupled to the transmission line structure.

13. The combination of claim 12, wherein the RFID device is an antennaless RFID device.

14. The combination of claim 13, wherein the antennaless RFID device includes an RFID chip and conductive leads connected to the chip.

15. The combination of claim 14, wherein the antennaless RFID device further includes an inductor connecting one of the conductive leads to another of the conductive leads.

16. The combination of claim 12, wherein the RFID device is an antennaed RFID device.

17. The combination of claim 12, wherein the RFID device is at least partially in a gap between the transmission lines.

18. The RFID device detection system of claim 1, wherein the proximity locator includes a load coupled to the conductors.

19. The RFID device detection system of claim 18, wherein the load is a terminating resistor.

20. The RFID device detection system of claim 1, wherein the conductors include a driven conductor between a pair of ground conductors.

21. The RFID device detection system of claim 20, wherein the driven conductor and the ground conductors are substantially co-planar.

22. The RFID device detection system of claim 21, wherein the driven conductor and the ground conductors are conductive strips.

23. The RFID device detection system of claim 20, wherein at least one of the ground portions is electrically coupled to a central portion that is substantially surrounded by a substantially annular portion of the central portion.

24. The RFID device detection system of claim 20, further comprising a coaxial cable that includes a central conductor and an outside conductor;

wherein one of the conductors of the cable is electrically connected to the ground conductors; and

wherein the other of the conductors of the cable is electrically connected to the driven conductor.

25. The RFID device detection system of claim 1, wherein at least one of the conductors includes a plurality of ridges thereupon.

26. The RFID device of detection system of claim 25, wherein adjacent pairs of the ridges define troughs therebetween;

and

wherein the troughs are configured to receive at least part of an RFID device.

27. The RFID device of detection system of claim 25, wherein the ridges each have a tapered shaped that is broader at a proximal base than at a distal end.

28. The RFID device detection system of claim 25, wherein the ridges include a resilient material.

29. The RFID device detection system of claim 28, wherein the ridges include a conductive material coating the resilient material.

30. The RFID device detection system of claim 1, wherein the system includes a first part that includes the reader;

wherein the system includes a second part that includes the at least two conductors; and

wherein the first and second parts are mechanically separable from one another.

31. The RFID device detection system of claim 30, wherein the reader and the conductors are electrically coupled when the first and second parts are mechanically couplable together.

32. The RFID device detection system of claim 31, wherein at least part of the first part separably fits into at least part of the second part, thereby mechanically coupling the parts together.

33. The RFID device detection system of claim 30, wherein at least part of the second part fits into a depression of the first part.

34. The RFID device detection system of claim 30,

wherein the first part includes a rack;

and

wherein the second part includes a hanger that is couplable to the rack.

35. The RFID device detection system of claim 34, wherein the hanger includes a hook couplable to the rack.

36. The RFID device detection system of claim 35, wherein the hook of the hanger fits into a depression in the rack.

37. The RFID device detection system of claim 36, wherein the depression is one of a plurality of depressions in the rack.

38. The RFID device detection system of claim 36, wherein the rack includes and the hook are electrically coupled when the hook is in the depression, so as to enable transmission of electrical signals between the reader and the conductors of the transmission line structure.

39. The RFID device detection system of claim 38, wherein the hook includes a pair of wires for electrically coupling with the rack.

40. The RFID device detection system of claim 39, wherein the wires include electrically-conductive material coated by a plastic material.

41. The RFID device detection system of claim 34, wherein the hanger includes a hanger bar for receiving a garment.

42. The RFID device detection system of claim 41, wherein the hanger bar includes and the conductors are relatively located such that a label of the garment is in close proximity to the conductors when the garment is on the hanger bar.

43. 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 coupled to the transmission line structure.

44. The method of claim 43, wherein the RFID devices include antennaless RFID devices.

45. The method of claim 44, 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.

46. The method of claim 43, wherein the powering includes capacitively coupling the transmission line structure and the RFID devices.

47. The method of claim 43, wherein the powering includes magnetically coupling the transmission line structure and the RFID devices.

48. The method of claim 43, wherein the RFID devices include antennaed RFID devices.

49. A method of tracking objects, comprising:

placing an RFID device 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.

50. The method of claim 49, wherein the RFID device is an antennaless RFID device.

51. The method of claim 49, wherein the RFID device is an antennaed RFID device.

52. The method of claim 49, wherein the detecting includes detecting changes in a short-range RF electric field produced by the proximity locator.

53. The method of claim 49, further comprising sending an alert when a predetermined situation is uncovered by the detecting.

54. The method of claim 53, wherein the predetermined situation is removal of an unusual number of objects over a predetermined time interval.

55. The method of claim 53, wherein the predetermined situation is removal of the objects out of order.

56. The method of claim 49, wherein the proximity detector includes a pair of transmission lines configured to produce a short-range RF electric field between the transmission lines.