Method and apparatus for selectively activating radio frequency identification tags that are in close proximity

• US 6,392,544 B1
• Filed: 09/25/2000
• Issued: 05/21/2002
• Est. Priority Date: 09/25/2000
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Quaderer, James G., Rakers, Patrick L., Rachwalski, Richard Stanley, Collins, Timothy James
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): Nguyen, Tai T.
• Application Number:
  US09/669,289
• Time in Patent Office: 603 Days
• Field of Search: 340/572.7, 340/568.1, 340/825.54, 340/571, 340/539, 340/572.1, 340/10.2, 340/10.1, 340/10.32, 340/10.31, 340/2.2, 340/5.91
• US Class Current: 340/572.7
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08
• CPC Class Codes: G06K 7/10316 using at least one antenna particularly designed for interrogating the wireless record carriers antennas in general H01Q1/22
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles

Abstract

A radio frequency identification exciter (200) includes a plurality of antenna elements (122a-i) that are spaced to define active areas (130a-e). A matrix switch (202) flexibly connects the plurality of antenna elements to an exciter circuit (203). Independent switches (204a-i) are selectively switched such that an electric field is generated between at least two antenna elements whereby radio frequency identification tags (132) in the vicinity of the two antenna elements are capacitively powered to exchange data with the exciter. Antenna elements other than the at least two antenna elements may be selectively coupled to a signal from the exciter circuit that inhibits activation of radio frequency identification tags in the vicinity of those antenna elements. The matrix switch preferably comprises polymer-based circuits.

Claims

1. An apparatus for capacitively powering radio frequency identification devices, the apparatus comprising:

a plurality of antenna elements;

an exciter, coupled to at least a first portion of the plurality of antenna elements, to provide an excitation signal used to selectively energize the first portion of the plurality of antenna elements; and

a switch selectively coupled to at least one of the plurality of antenna elements and the exciter,

wherein the exciter has a first potential terminal and a second potential terminal, and wherein at least one of the first potential terminal and the second potential terminal emits a radio frequency signal, and wherein a first antenna element of the plurality of antenna elements is coupled to the first potential terminal by the switch and a second antenna element is coupled to the second potential terminal by the switch such that a radio frequency identification tag between the first and second antenna elements is energized.

2. The apparatus of claim 1 further comprising a receiver coupled to at least a second portion of the plurality of antenna elements, and wherein the switch is selectively coupled to the receiver.

3. The apparatus of claim 1 wherein the apparatus is coupled to ground.

4. The apparatus of claim 1 wherein the plurality of antenna elements are electrostatic antenna elements.

5. The apparatus of claim 1 wherein at least one of the following elements is disposed on a substrate:

the plurality of antenna elements, and the switch.

6. The apparatus of claim 5 wherein the substrate is selected from a group consisting of:

contact paper, shelf lining, paper, plastic, rubber, and wood.

7. The apparatus of claim 1 wherein the switch comprises a plurality of independent switches, and wherein one independent switch of the plurality of independent switches controls at least one antenna element of the plurality of antenna elements, and wherein each of the plurality of independent switches is controllable separately by a switch control circuit.

8. The apparatus of claim 1 wherein the plurality of antenna elements are dispersed among a plurality of supports for holding articles.

9. The apparatus of claim 8 wherein the plurality of supports are shelves.

10. The apparatus of claim 1 wherein the plurality of antenna elements comprise polymers.

11. The apparatus of claim 1 wherein the switch comprises a transistor having conductive regions and insulating regions, and the conducting and insulating regions comprise polymers.

12. The apparatus of claim 11 wherein the polymers comprise at least one of:

carbon nanotubes, carbon fullerenes, conjugated semiconducting polymer, a high-density pi-bond organic oligomer, self assembled nanoparticles, and ceramic filled polymer dielectric.

13. The apparatus of claim 1 wherein each additional antenna element of the plurality of antenna elements other than the first and second antenna elements is coupled by the switch to the first potential terminal if the additional antenna element is closer to the first antenna element than the second antenna element, and wherein each additional antenna element of the plurality of antenna elements other than the first and second antenna elements is coupled to the second potential terminal if the additional antenna element is closer to the second antenna element than the first antenna element.

14. The apparatus of claim 1 wherein the first and second antenna elements are adjacent to each other.

15. The apparatus of claim 1 wherein the radio frequency identification tags between the first and second antenna elements are energized by an excitation signal to return a data signal to the exciter.

16. The apparatus of claim 1 wherein each of the plurality of antenna elements has a first surface and a second surface, and further comprising:

a protective cover formed over the first surface of each of the plurality of antenna elements; and

an adhesive layer formed on the second surface of each the plurality of antenna elements.

17. The apparatus of claim 16 wherein the conductive plate comprises carbon-based ink on a non-conductive substrate.

18. The apparatus of claim 17 wherein a portion of the protective cover is removed to expose the conductive plate and reveal a connection point and the connection point is used to couple the conductive plate to the switch.

19. The apparatus of claim 18 wherein a conductive tape couples the conductive plate to the switch.

20. The apparatus of claim 1 wherein the switch comprises variable capacitors that change their capacitance to control a flow of alternating current (AC) signals.

21. The apparatus of claim 1 wherein each additional antenna element of the plurality of antenna elements other than the first and second antenna elements is coupled by the switch to at least one of the first and second potential terminals such that a radio frequency identification tag not between the first and second antenna elements is not energized.

22. A method for capacitively activating radio frequency identification devices comprising the steps of:

selectively switching a first set of antenna elements to a first potential terminal of a circuit;

selectively switching a second set of antenna elements to a second potential terminal of a circuit, wherein at least one of the first and second potential terminals emits a radio frequency signal; and

establishing a potential of each antenna element such that at least two antenna elements have a potential difference.

23. The method of claim 22 further comprising the step of selectively switching a second set of antenna elements to a second switch to selectively receive data.

24. The method of claim 22 wherein the switch comprises a plurality of independent switches, and further comprising the steps of:

independently controlling at least one of the antenna elements of the plurality of antenna elements; and

separately controlling each of the plurality of independent switches.

25. The method of claim 22 further comprising the step of dispersing the plurality of antenna elements among a plurality of supports for holding articles.

26. The method of claim 22 further comprising the step of remotely powering the radio frequency identification tags in the vicinity of the at least two antenna elements by an excitation signal.

27. The method of claim 26 further comprising the step of receiving a data signal from the radio frequency identification tag.