Electromagnetic radiation decoupler

• US 20070096852A1
• Filed: 06/23/2006
• Published: 05/03/2007
• Est. Priority Date: 06/25/2005
• Status: Active Grant

• Current Assignee: HID Global Corporation (Assa Abloy AB)
• Original Assignee: Qinetiq Limited (QinetiQ Group PLC)
• Inventors: Brown, James, Clarke, Paul, Lawrence, Christopher, Damerell, William
• Granted Patent: US 7,768,400 B2
• Time in Patent Office: Days
• US Class Current: 333/195
• CPC Class Codes: G06K 19/07 with integrated circuit chips
• CPC Class Codes: G06K 19/07722 the record carrier being multilayered, e.g. laminated sheets flat articles in general, see B32B37/00
• CPC Class Codes: G06K 19/07749 the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
• CPC Class Codes: G06K 19/0776 the adhering arrangement being a layer of adhesive, so that the record carrier can function as a sticker
• CPC Class Codes: G06K 19/07771 the record carrier comprising means for minimising adverse effects on the data communication capability of the record carrier, e.g. minimising Eddy currents induced in a proximate metal or otherwise electromagnetically interfering object

Abstract

An electromagnetic radiation decoupler for decoupling radiation in the wavelength range λ_min to λ_max. The decoupler has a first conductor layer in contact with a dielectric layer which comprises at least one area of absence and the thickness of the decoupler is less than λ_min/4n, where n is the refractive index of the dielectric. The dielectric layer may be sandwiched between two conductor layers, one of which has the structure described above. The invention is also directed to methods of using and various articles comprising such a decoupler.

Claims

1. A radiation decoupler for an electronic device said decoupler comprising at least one dielectric layer sandwiched between at least one first conductor layer and at least one second conductor layer, wherein the at least one first conductor layer has at least one area of absence where the first conductor layer does not overlie the dielectric layer and the decoupler is adapted such that, in use, an electromagnetic field is enhanced in the vicinity of the area of absence of the first conductor layer.

3. A decoupler according to claim 1 wherein the second conductor layer is at least the same length as the first conductor layer.

4. A decoupler according to claim 1 wherein the electronic device is an RF tag.

5. A decoupler according to claim 1 wherein the thickness of the decoupler is less than λ

/4n, where n is the refractive index of the dielectric.

6. A decoupler according to claim 5 wherein the thickness of the decoupler is less than λ

/10.

7. A decoupler according to claim 6 wherein the thickness of the decoupler is less than λ

/300.

8. A decoupler according to claim 7 wherein the thickness of the decoupler is less than λ

/1000.

9. A decoupler according to claim 1 wherein the spacing G between at least one edge of the first conductor layer and the area of absence is determined by G≈

λ

/2n

where n is the refractive index of the dielectric, and λ

is the intended wavelength of operation of the decoupler

10. A decoupler according to claim 1 further comprising a third conductor layer adjacent a second dielectric layer wherein third conductor layer has at least one area of absence where the third conductor layer does not overlie the second dielectric layer and wherein the second dielectric layer is located between the third conductor layer and the second conductor layer.

11. A decoupler according to claim 10 wherein the length of the first conductor layer is different to the length of the third conductor layer.

12. A decoupler according to claim 1 wherein there are a plurality of areas of absence in the first conductor layer.

13. A decoupler according to claim 12 wherein the plurality of areas of absence are periodic in nature.

14. A decoupler according to claim 1 wherein the areas of absence are slit structures.

15. A decoupler according to claim 1 wherein the at least one area of absence of the first conductor layer divides the first conductor layer into at least two islands.

16. A decoupler according to claim 15 wherein at least one of the islands is of length G≈

λ

2n.

17. A decoupler according to claim 15 wherein the first conductor layer comprises at least 4 islands separated by two intersecting orthogonal slits

18. A decoupler according to claim 14 wherein there are at least two substantially parallel slits

19. A decoupler according to claim 18 wherein the of spacing of the at least two slits is determined by G≈

λ

/2n, where n is the refractive index of the dielectric and λ

is the intended wavelength of operation of the decoupler.

20. A decoupler according to claim 1 wherein the area of absence comprises three or more slits, said slits intersecting to form a polygon with n sides, where n is an integer of 3 or more.

21. A decoupler according to claim 14 wherein the slit width is less than 500 microns.

22. A decoupler according to claim 21 wherein the slit width is less than 150 microns.

23. A decoupler according to claim 22 wherein the slit width is less than 50 microns.

24. A decoupler as claimed in claim 1 wherein the dielectric layer is formed from a plastic, polymer, ceramic, glass, cardboard, corrugated cardboard, paper, or substantial void.

25. A decoupler according to claim 1 wherein the refractive index of the dielectric layer can be controllably varied.

26. A decoupler according to claim 25 further comprising for a refractive index controller.

27. A decoupler according to claim 1 wherein an RF tag is located in the vicinity of the area of absence of the first conductor layer and which is electrically isolated from said first conductor layer.

28. A decoupler according to claim 27 wherein the RF tag is a low Q RF tag.

29. A decoupler as claimed in claim 27, wherein the RF tag is electrically isolated from the first conductor layer and second conductor layer, and is located on, at least partly within or at the edge of the dielectric layer.

31. A decoupler as claimed in claim 17 wherein an RF tag is located substantially at the point of intersection of the intersecting orthogonal slits and which is electrically isolated from the first conductor layer.

32. A decoupler according to claim 1 wherein the main axis of the antenna of said RF tag is aligned substantially orthogonal to at least one edge of the first conductor layer.

33. A decoupler according to claim 27 wherein said RF tag is spaced above the surface of the decoupler at a distance of less than 2000 microns.

34. A decoupler according to claim 33 wherein a non-electrically conducting spacer is located between said decoupler and said RF tag.

35. A decoupler according to claim 34 wherein the thickness of the spacer and the substrate of the RF tag is together in the range of from 10 to 1000 microns.

36. A decoupler according to claim 35 wherein the thickness is in the range of from 175 to 800 microns.

37. A decoupler according to claim 1 comprising a protective housing over part, all or substantially all of the decoupler and/or RF tag.

38. A decoupler according to claim 1 wherein the decoupler is adapted so as to substantially decouple an electronic device mounted thereon from a surface which is a conductive material, a material which comprises a high liquid content or a surface which forms part of a containment means for a fluid.

39. A decoupler according to claim 38 wherein the conductive material is carbon, metal or metal alloys.

40. A decoupler according to claim 38 wherein the material which comprises a high liquid content is cellulose material, wood or naturally occurring material.

41. A decoupler according to claim 38, wherein the containment means is a food, drink, or chemical container.

45. An adhesive tape comprising at least one decoupler according to claim 1.

46. A body or container which comprises at least one decoupler according to claim 1.

47. A body or container according to claim 46 wherein at least one RF tag is located on said decoupler.

48. A body or container according to claim 47 wherein at least one surface of said body or container is curved.

51. A body or container according to claim 47 comprising a recessed portion within a surface of said body or container, said recess comprising a decoupler according to claim 1 and at least one RF tag located on said decoupler and optionally a protective layer to envelope said decoupler and RF tag, such that said decoupler and RF tag are at least flush with the surface of said body or container.

55. A method of tracking a body or a container comprising the steps of applying to a proportion of the surface of said body or container a decoupler according to claim 1 and at least one RF tag interrogating the at least one RF tag with RF radiation, detecting the response from the at least one RF tag.

56. A decoupler according to claim 3 wherein the dielectric layer, first conductor layer and second conductor layers, are substantially the same length, wherein said length G of all three layers is determined by λ

≈

2nG, wherein an RF tag is located at edge of the board substantially orthogonal to the plane of main axis of said decoupler and wherein the RF tag is electrically isolated from the first and second conductor layers, where n is the refractive index of the dielectric, and λ

is the intended wavelength of operation of the decoupler.

57. A decoupler according to claim 56 wherein the decoupler is double sided metal clad printed circuit board.

58. A decoupler according to claim 1 wherein the area of absence is substantially non parallel to at least one of the edges of the decoupler.

59. A decoupier according to claim 1 where at least one edge of the area of absence of the first conductor layer is a non-liner pattern.

60. A decoupler according to claim 59 wherein the area of absence of the first conductor layer comprises at least one circular pattern.

61. A decoupler according to claim 60 wherein the circular pattern is a circular slit in the first conductor layer.

62. A decoupler according to claim 1 wherein the dielectric layer is at least partly formed from packaging or labelling material of an article.

63. A decoupler according to claim 62, wherein the packaging or labelling material is a natural or man made fibre, plastic, cellulose, glass, cardboard, corrugated cardboard or ceramic.

64. A low Q RF tag suitable for use on a decoupler according to claim 1 wherein the antenna has a major dimension substantially less than 2 cm.

65. A low Q RF tag according to claim 64, wherein the antenna has a major dimension substantially less than 1 cm.

66. A low Q RF tag according to claim 65 mounted on a decoupler according to claim 1, wherein there is a spacer located between said low Q RF tag and decoupler.

67. A low Q RF tag according to claim 66 wherein the thickness of the spacer and the low Q RF tag together is in the range of from 175 to 800 microns.

68. A kit of parts comprising an RF tag or a low Q RF tag, with an optional spacer and a decoupler according to claim 1.

69. A method of detection or identification of a surface comprising the steps of

i) bringing together a non conducting surface comprising a low Q RF tag with an optional spacer located on the upper surface of said low Q RF tag

ii) bring said surface into a proximate relationship with a decoupler according to claim 1,

iii) interrogating said low Q RF tag, wherein said low Q RF tag can only be read when in close proximity to said decoupler.

70. A method of forming a decoupler suitable for the detection or identification of a surface comprising the steps of

i) providing a non conducting surface comprising an RF tag or low Q RF tag with an optional spacer located on the upper surface of said RF tag, and at least one first conductor layer in contact with part or substantially all of at least one dielectric layer, wherein the at least one first conductor layer has at least one area of absence where the first conductor layer does not overlie the dielectric layer,

ii) bringing together the surface of step i) with a second conductor layer or conducting surface to form a decoupler as claimed, in claim 1.

2. A radiation decoupler for an electronic device, for decoupling radiation from a conducting surface, said decoupler comprising at least one conductor layer in contact with at least one dielectric layer, wherein the at least one first conductor layer has at least one area of absence where the first conductor layer does not overlie the dielectric layer and the decoupler is adapted such that, in use, an electromagnetic field is enhanced in the vicinity of the area of absence of the first conductor layer.

30. A decoupler according to claim 2 wherein an RF tag is located in the vicinity of the area of absence of the first conductor layer and which is electrically isolated from said first conductor layer.

44. A decoupler as claimed in claim 2, further comprising a means of attaching the decoupler to the surface such that the dielectric layer is adjacent the conducting surface.

49. A metallic body or container wherein a proportion of the surface of the container is covered in a decoupler according to claim 2.

50. A metallic body or container according to claim 49 wherein at least one RF tag is located on said decoupler.

52. A metallic body or container according to claim 50 comprising a recessed portion within a surface of said body or container, said recess comprising a decoupler according to claim 2 which first conductor layer is electrically isolated from said surface and at least one RF tag located on said decoupler and optionally a protective layer to envelope said decoupler and RF tag, such that said decoupler and RF tag are at least flush with the surface of said body or container.

42. A decoupler for decoupling an RF tag from a surface comprising a dielectric layer sandwiched between a first conductor layer and a second conductor layer wherein the resonant frequency of the decoupler is selected to substantially match the resonant frequency of the RF tag and/or a RF interrogating source and wherein at least one edge of the first conductor layer does not extend to the edge of the dielectric layer, the gap between the edge of the first conductor layer and the dielectric layer being smaller than the wavelength of EM radiation at the resonant frequency.

43. A decoupler for decoupling an RF tag from a conducting surface comprising at least one conductor layer in contact with at least one dielectric layer surface wherein the resonant frequency of the decoupler is selected to substantially match the resonant frequency of the RF tag and/or a RF interrogating source and wherein at least one edge of the first conductor layer does not extend to the edge of the dielectric layer, the gap between the edge of the first conductor layer and the dielectric layer being smaller than the wavelength of EM radiation at the resonant frequency.

53. A method of making a decoupler with a corrugated cardboard dielectric core, comprising the steps of placing a first conductor layer on a first cardboard layer, placing a second conductor layer on a second cardboard layer, bringing said first and second cardboard layers together and adjoining them with a corrugated cardboard insert such that there is at least one area of absence on the first conductor layer on the first cardboard layer which overlies the second conductor layer.

54. A method according to claim 53 wherein said first conductor layer is located on the inner surface of said first cardboard layers adjacent said corrugated cardboard insert and/or said second conductor layer is located on the inner surface of said second cardboard layers adjacent said corrugated cardboard insert.

71. A single island decoupler for an RF tag for decoupling said device from a surface comprising at least one dielectric layer sandwiched between at least one first conductor layer and at least one second conductor layer, wherein the first conductor layer is tuned to the resonant frequency of the interrogating radiation, wherein said length G of the first conductor layer is determined by λ

≈

2nG, wherein the at least one first conductor layer has one area of absence at, at least one edge, such that the first conductor layer does not overlie the dielectric layer, wherein an RF tag, which is electrically isolated from the first conductor layer, is located in the vicinity of the area of absence of the first conductor layer.

72. A single island decoupler for an RF tag for decoupling said device from a surface comprising at least one dielectric layer sandwiched between at least one first conductor layer and at least one second conductor layer, wherein the first and second conductor layers are independently tuned to a resonant frequency of interrogating radiation, wherein said length G of the said conductor layer is determined by λ

≈

2nG, wherein an RF tag, which is electrically isolated from said first and second conductor layer, is located in the vicinity of an area of absence on said dielectric layer.

73. A single island decoupler for an RF tag for decoupling said device from a surface comprising at least one dielectric layer sandwiched between at least one first conductor layer and at least one second conductor layer, wherein the first conductor layer is tuned to the resonant frequency of a first interrogating radiation, and the second conductor layer is tuned to the resonant frequency of a second interrogating radiation, wherein said length G of the first conductor layer and second conductor layer is determined by λ

≈

2nG, wherein the first and second conductor layers have one area of absence at, at least one edge, such that the area of absence of the first conductor layer does not overlie the dielectric layer or area of absence on the second conductor layer, wherein an RF tag, which is electrically isolated, is located in the vicinity of the area of absence of the first conductor layer and optionally a further RF tag, is located in the vicinity of the area of absence of the second conductor layer.