Radio frequency identification device for increasing tag activation distance and method thereof

• US 6,825,754 B1
• Filed: 09/11/2000
• Issued: 11/30/2004
• Est. Priority Date: 09/11/2000
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rolin, John Howard
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): BANGACHON, WILLIAM L
• Application Number:
  US09/659,807
• Time in Patent Office: 1,541 Days
• Field of Search: 340/10.34, 340/10.31, 340/10.32, 340/10.33, 340/572.1, 340/572.3, 340/572.2, 340/572.4, 340/10.51, 340/10.6, 235/492, 235/491, 235/439
• US Class Current: 340/10.34
• 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 19/07756 the connection being non-galvanic, e.g. capacitive

Abstract

A radio frequency identification (“RFID”) device for increasing tag activation distance comprises a first exciter electrode (2), a second exciter electrode (21), a dielectric substrate (3), and a first exciter voltage source (4). The second exciter electrode is positioned behind the first exciter electrode. The dielectric substrate is disposed between the first and second exciter electrodes. The dielectric substrate isolates the first exciter electrode from the second exciter electrode. The first exciter voltage source is coupled to at least one of the first exciter electrode and the second exciter electrode.

Claims

1. A radio frequency identification (“

RFID”

) reader for increasing tag activation distance, the RFID reader comprising;

at least a first exciter electrode and a second exciter electrode, the second exciter electrode positioned behind the first exciter electrode;

a dielectric substrate disposed between the first and second exciter electrodes, and isolating the first exciter electrode from the second exciter electrode; and

a first exciter voltage source coupled to at least one of the first exciter electrode and the second exciter electrode for generating an electric field that radiates in a front portion of the RFID reader.

2. The RFID reader of claim 1 wherein the first exciter voltage source is coupled to the first exciter electrode, and further comprising a second exciter voltage source coupled to the second exciter electrode.

3. The RFID reader of claim 2 wherein the first exciter voltage source produces alternating currents in phase with the second exciter voltage source.

4. The RFID reader of claim 2 wherein the first exciter voltage source produces alternating currents out of phase with the second exciter voltage source.

5. The RFID reader of claim 2 wherein the first exciter voltage source and the second exciter voltage sources produce alternating currents at the same frequencies.

6. The RFID reader of claim 2 wherein the first exciter voltage source and the second exciter voltage source produce alternating currents at different frequencies.

7. The RFID reader of claim 2 wherein the first exciter voltage source and the second exciter voltage source produce alternating currents at different voltages.

8. The RFID reader of claim 2 wherein the first exciter voltage source and the second exciter voltage source produce alternating currents at the same voltages.

9. The RFID reader of claim 1 further comprising a conductor connecting the first exciter electrode to the second exciter electrode.

10. The RFID reader of claim 1 wherein the dielectric substrate is a printed circuit board.

11. The RFID reader of claim 1 wherein the first exciter electrode and the second exciter electrode have non-identical geometries.

12. The RFID reader of claim 1 wherein the first exciter electrode and the second exciter electrode have identical geometries.

13. The RFID reader of claim 1 wherein the first exciter electrode and the second exciter electrode are not coplanar.

14. The RFID reader of claim 1 wherein the first exciter electrode is electrically coupled to the first exciter voltage source, and the second exciter electrode is not electrically coupled through a conductor to any electrical potential within the RFID device.

15. The RFID reader of claim 1 wherein the first exciter electrode is electrically coupled to the first exciter voltage source, and the second exciter electrode is electrically coupled to a voltage divider.

16. The RFID reader of claim 1 further comprising electronic circuitry coupled to the first exciter electrode and the second exciter electrode.

17. A radio frequency identification (“

RFID”

) reader for increasing tag activation distance, the RFID device comprising;

at least a first exciter electrode and a second exciter electrode, the first and second exciter electrodes electrically coupled continuously along their edges to form a conductive volume; and

a first exciter voltage source coupled to the first and second exciter electrodes for generating an electric field that radiates in a front portion of the RFID reader.

18. The RFID reader of claim 17 wherein the electrical connection and the first and second exciter electrodes are formed in a continuous electrically conductive sheet without any intervening dielectric material.

19. A method for increasing tag activation distance in a radio frequency identification (“

RFID”

) reader, the method comprising;

providing at least a first exciter electrode and a second exciter electrode;

positioning the second exciter electrode behind the first exciter electrode;

disposing a dielectric substrate between the first and second exciter electrodes; and

electrically coupling a first exciter voltage source to at least one of the first exciter electrode and the second exciter electrode for generating an electric field that radiates in a front portion of the RFID reader.

20. The method of claim 19 wherein the step of disposing comprises isolating the first exciter electrode from the second exciter electrode.

21. The method of claim 19 further comprising electrically coupling the first exciter electrode to the second exciter electrode.

22. The method of claim 19 further comprising dynamically varying at least one of a magnitude and phase of the first exciter voltage source.