Frequency-based wireless monitoring and identification using spatially inhomogeneous structures

• US 6,724,310 B1
• Filed: 10/10/2000
• Issued: 04/20/2004
• Est. Priority Date: 10/10/2000
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Gershenfeld, Neil, Fletcher, Richard
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): NGUYEN, HUNG T
• Application Number:
  US09/685,819
• Time in Patent Office: 1,288 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.4, 340/572.5
• US Class Current: 340/572.4
• CPC Class Codes: G08B 13/2414 using inductive tags
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2448 Tag with at least dual detection means, e.g. combined inductive and ferromagnetic tags, dual frequencies within a single technology, tampering detection or signalling means on the tag

Abstract

Wireless tags have a plurality of non-equivalent current pathways, each of which responds differently to an interrogation signal and collectively represent encoded information. The element is subjected to the signal, stimulating the current pathways, each of which contributes to an overall element response. The individual contributions and, hence, the information may be recovered from this overall response. The response of each of the pathways to the signal may vary in terms of one or more of resonant frequency, amplitude, damping, and Q factor.

Claims

1. A method of sensing information, the method comprising:

a. providing a device responsive to a wireless electromagnetic signal and having plurality of non-equivalent current pathways, each of the pathways responding differently to the signal and collectively representing the information, wherein the device comprises a pair of parallel, electrically conductive loops and at least one conductive crossbar sandwiched therebetween, with a dielectric material intervening between the at least one crossbar and the loops;

b. subjecting the device to the wireless electromagnetic signal; and

c. recovering the information based on interaction between the device to the signal.

2. The method of claim 1 wherein each of the pathways exhibits a different electrical response to the signal, the responses characterizing the information and differing in at least one of resonant frequency, amplitude, damping, and Q factor.

3. The method of claim 2 wherein each of the pathways corresponds to a different capacitance.

4. The method of claim 2 wherein each of the pathways corresponds to a different inductance.

5. The method of claim 1 wherein the device has at least two conductive crossbars.

6. The method of claim 5 wherein each crossbar has a position relative to the loops, each crossbar position contributing to a resonant frequency of the device.

7. The method of claim 5 wherein each crossbar has a width, each crossbar width contributing to a resonant frequency and a Q factor at that frequency.

8. The method of claim 5 wherein:

a. the crossbars have an average spacing therebetween; and

b. subjection comprises generating the electromagnetic signal and sending the signal through an antenna, the antenna comprising a series of loops having an average size approximating the average spacing between crossbars.

9. The method of claim 1 further comprising:

a. providing a second device responsive to a wireless electromagnetic signal and having plurality of non-equivalent circuit pathways, each of the pathways responding differently to the signal and collectively representing additional information, wherein the second device comprises a pair of electrically conductive loops and a conductive crossbar sandwiched therebetween, with a dielectric material intervening between the crossbar and the loops; and

b. electrically coupling the devices so as to facilitate joint detection of the information and the additional information.

10. The method of claim 9 wherein the devices are coupled at least capacitively.

11. The method of claim 9 wherein the devices are coupled at least inductively.

12. A device responsive to a wireless electromagnetic signal and having a plurality of non-equivalent current pathways representing information, each of the pathways responding differently to the signal to convey the information, wherein the non-equivalent current pathways comprise a pair of parallel, electrically conductive loops and at least one conductive crossbar sandwiched therebetween, with a dielectric material intervening between the at least one crossbar and the loops.

13. The device of claim 12 wherein each of the pathways exhibits a different electrical response to the signal, the responses characterizing the information and differing in at least one of resonant frequency, amplitude, damping, and Q factor.

14. The device of claim 13 wherein each of the pathways corresponds to a different capacitance.

15. The device of claim 13 wherein each of the pathways corresponds to a different inductance.

16. The device of claim 12 wherein the device has at least two conductive crossbars.

17. The device of claim 16 wherein each crossbar has a position relative to the loops, each crossbar position contributing to a resonant frequency of the device.

18. The device of claim 16 wherein each crossbar has a width, each crossbar width contributing to a resonant frequency and a Q factor at that frequency.

19. The device of claim 12 further comprising a second device responsive to a wireless electromagnetic signal and having a plurality of non-equivalent current pathways representing additional information, each of the pathways responding differently to the signal to convey the additional information, wherein the second device comprises a pair of electrically conductive loops and a conductive crossbar sandwiched therebetween, with a dielectric material intervening between the crossbar and the loops, the devices being electrically coupled so as to facilitate joint detection of the information and the additional information.

20. The device of claim 19 wherein the devices are coupled at least capacitively.

21. The device of claim 19 wherein the devices are coupled at least inductively.

22. A method of sensing information, the method comprising:

a. providing a device responsive to a wireless electromagnetic signal and having a plurality of non-equivalent current pathways, each of the pathways responding differently to the signal and collectively representing the information, wherein the device comprises a pair of parallel, electrically conductive elements each patterned to form a single structure having at least two open loops, the elements being electrically connected so as to share a backbone current path and opposed so as to substantially overlap spatially, with a dielectric material sandwiched between the opposed elements;

b. subjecting the device to the wireless electromagnetic signal; and

c. recovering the information based on interaction between the device to the signal.

23. The method of claim 22 wherein each of the opposed open loops has an opposite turn direction.

24. The method of claim 22 wherein each of the open loops has a length and an associated resonant frequency dependent on the length, the lengths being different so as to produce different resonant frequencies.

25. The method of claim 22 wherein each of the pathways exhibits a different electrical response to the signal, the responses characterizing the information and differing in at least one of resonant frequency, amplitude, damping, and Q factor.

26. The method of claim 25 wherein each of the pathways corresponds to a different capacitance.

27. The method of claim 25 wherein each of the pathways corresponds to a different inductance.

28. A method of sensing information, the method comprising:

a. providing a device responsive to a wireless electromagnetic signal and having a plurality of non-equivalent current pathways, each of the pathways responding differently to the signal and collectively representing the information;

b. subjecting the device to the wireless electromagnetic signal; and

c. recovering the information based on interaction between the device to the signal, wherein the device comprises a plurality of pairs of stacked, electrically conductive elements and;

each element is patterned to form a single structure having at least one open loop;

each pair of elements is electrically connected so as to share a backbone current path;

the elements of each element pair are opposed so as to substantially overlap spatially;

a dielectric material is sandwiched between the elements of each element pair;

the element pairs are electrically coupled without direct connection therebetween; and

each element pair exhibits a separately detectable electrical response corresponding to information associated therewith.

29. The method of claim 28 wherein for each pair of elements, the open loops of one of the elements have a first turn direction and the open loops of the other element have a second turn direction opposite to the first turn direction.

30. The method of claim 28 wherein each element comprises a plurality of open loops each having a length and an associated resonant frequency dependent on the length, the lengths being different so as to produce different resonant frequencies.

31. The method of claim 28 wherein the element pairs are coupled at least capacitively.

32. The method of claim 28 wherein the element pairs are coupled at least inductively.

33. The method of claim 28 wherein each of the pathways exhibits a different electrical response to the signal, the responses characterizing the information and differing in at least one of resonant frequency, amplitude, damping, and Q factor.

34. The method of claim 33 wherein each of the pathways corresponds to a different capacitance.

35. The method of claim 33 wherein each of the pathways corresponds to a different inductance.

36. A device responsive to a wireless electromagnetic signal and having a plurality of non-equivalent current pathways representing information, each of the pathways responding differently to the signal to convey the information, wherein the non-equivalent current pathways comprise:

a. a pair of parallel, electrically conductive elements each patterned to form a single structure having at least two open loops, the elements being electrically connected so as to share a backbone current path and opposed so as to substantially overlap spatially; and

b. a dielectric material sandwiched between the opposed elements.

37. The device of claim 36 wherein each of the opposed open loops has an opposite turn direction.

38. The device of claim 36 wherein each of the open loops has a length and an associated resonant frequency dependent on the length, the lengths being different so as to produce different resonant frequencies.

39. The device of claim 36 wherein each of the pathways exhibits a different electrical response to the signal, the responses characterizing the information and differing in at least one of resonant frequency, amplitude, damping, and Q factor.

40. The device of claim 39 wherein each of the pathways corresponds to a different capacitance.

41. The device of claim 39 wherein each of the pathways corresponds to a different inductance.

42. A device responsive to a wireless electromagnetic signal and having a plurality of non-equivalent current pathways representing information, each of the pathways responding differently to the signal to convey the information, wherein the non-equivalent current pathways comprise a plurality of pairs of stacked, electrically conductive elements and:

each element is patterned to form a single structure having at least one open loop;

each pair of elements is electrically connected so as to share a backbone current path;

the elements of each element pair are opposed so as to substantially overlap spatially;

a dielectric material is sandwiched between the elements of each element pair;

the element pairs are electrically coupled without direct connection therebetween; and

each element pair exhibits a separately detectable electrical response corresponding to information associated therewith.

43. The device of claim 42 wherein for each pair of elements, the open loops of one of the elements have a first turn direction and the open loops of the other element have a second turn direction opposite to the first turn direction.

44. The device of claim 42 wherein each element comprises a plurality of open loops each having a length and an associated resonant frequency dependent on the length, the lengths being different so as to produce different resonant frequencies.

45. The device of claim 42 wherein the element pairs are coupled at least capacitively.

46. The device of claim 42 wherein the element pairs are coupled at least inductively.

47. The device of claim 42 wherein each of the pathways exhibits a different electrical response to the signal, the responses characterizing the information and differing in at least one of resonant frequency, amplitude, damping, and Q factor.

48. The device of claim 47 wherein each of the pathways corresponds to a different capacitance.

49. The device of claim 47 wherein each of the pathways corresponds to a different inductance.