Sensing properties of a material loading a UHF RFID tag by analysis of the complex reflection backscatter at different frequencies and power levels

• US 20120182147A1
• Filed: 01/18/2011
• Published: 07/19/2012
• Est. Priority Date: 01/18/2011
• 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 8,947,236 B2
• Time in Patent Office: Days
• US Class Current: 340/572.7
• CPC Class Codes: G06K 19/077 Constructional details, e.g. mounting of circuits in the carrier
• 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
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407

Abstract

An RFID device for sensing the properties of a material in proximity to a UHF tag. The RFID device includes a microchip, an antenna operatively coupled to the microchip, and an impedance transforming section operatively coupled to the microchip and to the antenna. Changing an electrical characteristic of at least one component of the RFID device results in a complex reflected signal at a reader device representing a sensed state of a material in proximity to the RFID device.

Claims

1. An RFID device comprising:

a microchip;

an antenna operatively coupled to the microchip;

an impedance transforming section operatively coupled to the microchip and to the antenna;

wherein changing an electrical characteristic of at least one component of the RFID device results in a complex reflected signal at a reader device representing a sensed state of a material in proximity to the RFID device.

2. The RFID device of claim 1 wherein the device operates at an ultra high frequency.

3. The RFID device of claim 1 wherein the device operates in the 902-928 MHz band.

4. The RID device of claim 1 wherein the electrical characteristic of the RFID device component comprises a complex impedance.

5. The RFID device of claim 1 wherein the material sensed comprises an analyte applied to the antenna and the changed electrical characteristic comprises an impedance of the antenna.

6. The RFID device of claim 1 wherein the material sensed is an analyte applied to the transforming section and the changed electrical characteristic comprises an impedance of the transforming section.

7. The RFID device of claim 1 wherein the material sensed is an analyte applied to both the antenna and the transforming section and the changed electrical characteristics comprises an impedance of the antenna and an impedance of the transforming section.

8. The RFID device of claim 1 wherein the complex reflected signal comprises a combination of an amplitude modulation and a phase modulation.

9. The RFID device of claim 1 wherein the transforming section comprises a loop of conductor material having a pair of connection points for coupling the microchip to the transforming section.

10. The RFID device of claim 1 wherein the transforming section comprises a loop of conductor material having a single connection point for coupling the microchip to the transforming section.

11. The RFID device of claim 1 wherein the transforming section comprises a loop of conductor material that is coupled to the microchip by an electromagnetic field.

12. The RFID device of claim 1 wherein the conductor material comprises any one of copper, aluminum, and silver.

13. The RFID device of claim 1 wherein the transforming section comprises a loop of conductor material having a pair of connection points for coupling the microchip to the transforming section.

14. The RFID device of claim 1 wherein the antenna comprises a dipole antenna.

15. The RFID device of claim 1 wherein the antenna and transforming section are combined as a single structure.

16. The RFID device of claim 1 wherein the sensed material has a complex dielectric constant that changes in response to an environmental factor.

17. The RFID device of claim 1 wherein the RFID device is attached to the material being sensed.

18. The RFID device of claim 1 wherein the material being sensed is applied to a specific region of the antenna.

19. The RFID device of claim 1 wherein the material being sensed is applied to both a specific region of the antenna and to the transforming section.

20. The RFID device of claim 1 wherein a first sensing material is applied to the antenna and a second sensing material is applied to the transforming section.

21. An RFID device comprising:

a microchip;

a combined structure operatively coupled to the microchip and including an antenna section and a conductor loop wherein the conductor loop functions as an impedance transforming section;

wherein an environmentally sensitive material added to the structure causes a change in an electrical characteristic of the combined structure in response to a signal from an RFID reader resulting in a complex reflected signal received at the reader representing a sensed state of the material.

22. The RFID device of claim 21 wherein the conductor loop comprises any one of copper, aluminum, and silver.

23. The RFID device of claim 21 wherein the conductor loop includes at least one connection point for coupling the microchip to the combined structure.

24. The RFID device of claim 21 wherein the antenna section comprises a dipole antenna.

25. The RFID device of claim 21 wherein the RFID device operates at an ultra high frequency between 902-928 MHz.

26. The RFID device of claim 21 wherein the environmentally sensitive material comprises an analyte.

27. The RFID device of claim 21 wherein the environmentally sensitive material comprises a concentration of an interferer.

28. The RFID device of claim 21 wherein the environmentally sensitive material is applied to the antenna section.

29. The RFID device of claim 21 wherein the environmentally sensitive material is applied to the conductor loop.

30. The RFID device of claim 21 wherein the environmentally sensitive material is applied to the conductor loop and to the antenna section.

31. The RFID device of claim 21 wherein the antenna section and the conductor loop are covered by different environmentally sensitive materials.

32. The RFID device of claim 21 wherein the change in electrical characteristic of the combined structure is controlled by varying the incident radio frequency power transmitted by the reader and measuring the amplitude and phase modulation of the reflected signal.