Photoconductive multi-resonator chipless RFID

• US 9,691,048 B1
• Filed: 12/22/2015
• Issued: 06/27/2017
• Est. Priority Date: 12/22/2015
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Gibson, George A., Larson, James R.
• Primary Examiner(s): Mikels, Matthew
• Application Number:
  US14/979,326
• Publication Number:
  US 20170178059A1
• Time in Patent Office: 553 Days
• Field of Search: 235487, 235492
• CPC Class Codes: G06K 19/0672 with resonating marks
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06Q 10/087 Inventory or stock management, e.g. order filling, procurement or balancing against orders

Abstract

A chipless RFID transponder is disclosed. The transponder comprises an antenna and a plurality of resonant structures that together define a spectral signature of the RFID transponder. Each of the resonant structures comprises conductive portions separated by interstitial regions. A reversible photoconductive material is disposed in the interstitial regions of the resonant structures between the conductive portions. The photoconductive material is positioned so as to shift the spectral signature of the RFID when exposed to radiation.

Claims

1. A chipless RFID transponder, comprising:

an antenna and a plurality of resonant structures that together define a spectral signature of the RFID transponder, each of the resonant structures comprising conductive portions separated by interstitial regions; and

a reversible photoconductive material disposed in the interstitial regions of the resonant structures between the conductive portions, the photoconductive material positioned so as to shift the spectral signature of the RFID when exposed to radiation, wherein the photoconductive material has a property of having a first conductivity prior to being exposed to radiation at a specified wavelength and a second conductivity that is different from the first conductivity after being exposed to radiation at the specified wavelength.

2. The chipless RFID transponder of claim 1, wherein the conductive portions of each resonant structure are formed from a continuous segment of electrically conductive material that is coplanar with the interstitial regions.

3. The chipless RFID transponder of claim 1, wherein the photoconductive material is an electrical insulator prior to being exposed to radiation at the specified wavelength.

4. The chipless RFID transponder of claim 1, wherein the second conductivity is higher than the first conductivity.

5. The chipless RFID transponder of claim 1, wherein the change in value of the second conductivity relative to the first conductivity is substantially linearly dependent on the intensity of the light to which the photoconductive material is exposed.

6. The chipless RFID transponder of claim 1, wherein the value of the second conductivity is substantially the same as the first conductivity unless the photoconductor is exposed to radiation having a threshold intensity.

7. The chipless RFID transponder of claim 1, further comprising at least one of an optical filter or a converter disposed over the plurality of resonant structures.

8. The chipless RFID transponder of claim 1, wherein the photoconductive material is disposed on a plurality of the resonant structures.

9. The chipless RFID transponder of claim 1, further comprising an adhesive backing on which the RFID transponder is disposed.

10. The chipless RFID transponder of claim 1, further comprising a security overlayer.

11. The chipless RFID transponder of claim 1, wherein the photoconductor is inorganic.

12. The chipless RFID transponder of claim 1, wherein the photoconductor comprises an organic polymer.

19. The chipless RFID transponder of claim 1, wherein the resonant structures are spiral resonators.

20. The chipless RFID transponder of claim 1, wherein the reversible photoconductor material is selected from the group consisting of selenium, tellurium, selenium tellurium, titanium dioxide, arsenic triselenide and doped amorphous silicon.

13. A method of tracking inventory, comprising:

placing a chipless RFID transponder on an article, the RFID transponder comprising,

an antenna and a plurality of resonant structures that together define a spectral signature of the RFID transponder, each of the resonant structures comprising conductive portions separated by interstitial regions; and

a reversible photoconductive material disposed in the interstitial regions of the resonant structures between the conductive portions, the photoconductive material positioned so as to shift the spectral signature of the RFID when exposed to radiation, wherein the photoconductive material has a property of having a first conductivity prior to being exposed to radiation at a specified wavelength and a second conductivity that is different from the first conductivity after being exposed to radiation at the specified wavelength.

14. The method of claim 13, further comprising detecting a spectral response of the at least one RFID transponder.

15. The method of claim 14, further comprising determining if the RFID transponder has been exposed to radiation based on the detected spectral response.

16. The method of claim 14, wherein the detecting comprises administering at least one interrogating pulse emitted by an interrogator, the at least one interrogating pulse comprising a spectral range.

17. The method of claim 14, wherein the conductive portions of each resonant structure are formed from a continuous segment of electrically conductive material that is coplanar with the interstitial regions.

18. A chipless RFID transponder, comprising:

an antenna and a plurality of resonant structures that together define a spectral signature of the RFID transponder, each of the resonant structures comprising conductive portions separated by interstitial regions; and

a reversible photoconductive material disposed in the interstitial regions of two or more of the resonant structures, the photoconductive material positioned so as to shift the spectral signature of the RFID when exposed to radiation, wherein the photoconductive material has a property of having a first conductivity prior to being exposed to radiation at a specified wavelength and a second conductivity that is different from the first conductivity after being exposed to radiation at the specified wavelength.