Switchable Radiation Enhancement and Decoupling

• US 20110037541A1
• Filed: 12/13/2007
• Published: 02/17/2011
• Est. Priority Date: 12/14/2006
• Status: Active Grant

• Current Assignee: HID Global Corporation (Assa Abloy AB)
• Original Assignee: Omni-Id Limited (Assa Abloy AB)
• Inventors: Brown, James Robert, Lawrence, Christopher Robert, Duncombe, Richard James, Johnson, Daniel Robert, Clarke, Paul Richard, Damerell, William Norman
• Granted Patent: US 8,453,936 B2
• Time in Patent Office: Days
• US Class Current: 333/219.1
• CPC Class Codes: G06K 19/0726 the arrangement including a circuit for tuning the resonance frequency of an antenna on the record carrier
• 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 19/07771 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
• CPC Class Codes: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal

Abstract

A device capable of enhancing an electric field to drive an electromagnetic tag into operation is switchable between states to control operation of the tag. Enhancement is provided by a dielectric cavity structure defined between first and second conducting layers. Different states of the device may have different resonant frequencies and read ranges according to the characteristics of the enhancement. As such a container can be provided which includes a tag which switches states on opening, allowing improved tracking characteristics.

Claims

1. Apparatus comprising a resonant dielectric cavity defined between first and second conducting layers, said apparatus having a first state in which an electromagnetic field of a first frequency is enhanced adjacent to said first layer, and a second state in which an electromagnetic field of said first frequency is substantially unaffected, said component being switchable between said first state and said second state by an external stimulus.

2. Apparatus according to claim 1, wherein said stimulus is the removal of at least part of said first or second conducting layer.

3. Apparatus according to claim 2, wherein removal results in a change of length of said first layer.

4. Apparatus according to claim 1, wherein either said first or said second conducting layer comprises a weakened or perforated portion to facilitate said removal of material.

5. Apparatus according to claim 1, wherein a release layer is included between said dielectric and either of said first or second conducting portions to facilitate said removal.

6. Apparatus according to claim 1, wherein said first layer is adapted to be removable by scratching.

7. Apparatus according to claim 1, wherein at least a portion of said dielectric is adapted to change between a substantially non conducting state and a conducting state on application of said stimulus.

8. Apparatus according to claim 1, wherein at least a portion of said dielectric is adapted to change dielectric constant on application of said stimulus.

9. Apparatus according to claim 7, wherein said stimulus comprises applying an RF field of a predetermined frequency.

10. Apparatus according to claim 7, wherein said stimulus comprises exposure to UV radiation.

11. Apparatus according to claim 7, wherein the stimulus comprises an applied electric potential.

12. Apparatus according to claim 7, wherein said dielectric is porous.

13. Apparatus according to claim 1, wherein said electromagnetic field is enhanced by a factor greater than or equal to 50, 100, or 200.

14. Apparatus according to claim 1, wherein an electromagnetic field of a second frequency is enhanced at said mounting site in said second state.

15. Apparatus according to claim 1 including an EM tag located at an edge of said cavity in a field enhancement region wherein in the first state the field enhancement is sufficient for the EM tag to be readable, and in the second state the field enhancement is insufficient for the EM tag to be readable at a given frequency and read range.

16. A device according to claim 15, wherein said tag is powered by differential capacitive coupling.

17. A device according to claim 15, wherein the EM tag is a low Q RFID tag.

18. Apparatus according to claim 1, wherein said apparatus can be returned to said first state by a further external stimulus.

35. The apparatus of claim 15 wherein the electromagnetic properties of said dielectric vary in response to a change in environmental conditions, thereby changing the degree of enhancement between a first state in which the EM tag is readable, and a second state in which the tag is unreadable, at a given frequency and read range.

36. Apparatus according to claim 1, wherein the first conducting layer does not overlie the second conducting layer in at least one area of absence.

37. Apparatus according to claim 36, wherein a tag is mounted or adapted to be mounted at said area of absence.

38. Apparatus according to claim 37 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 A is the intended wavelength of operation of the decoupler.

39. Apparatus according to claim 38 wherein the areas of absence are slit structures.

40. Apparatus according to claim 39 wherein the slit width is less than 500 microns.

41. Apparatus according to claim 1, wherein said first layer and said second layer are electrically connected at one edge.

43. Apparatus according to claim 41, wherein the second conducting side wall has a continuous length measured from the conducting base portion which is at least as long as the length of the first conducting side wall.

44. Apparatus according to claim 15, wherein said EM tag is electrically isolated from said first conductor layer.

45. Apparatus according to claim 1, wherein the total thickness of the component is less than λ

/4, or λ

/10, or λ

/300 or λ

/1000, where λ

is the intended wavelength of operation at said first frequency.

46. Apparatus according to claim 1, wherein the total thickness of the component or is 1 mm or less, or 500 μ

m or less, or 100 μ

m or less.

47. Apparatus according to claim 1, wherein one of the conductor layers forms part, or substantially all of a metallic body.

19-34. -34. (canceled)

42. Apparatus according to claim 42, wherein the length of the first conducting layer is approximately λ

/4 measured from the conducting edge portion, where λ

is the wavelength, in the dielectric material, of EM radiation at the frequency of operation v.

48. (canceled)