Radio frequency identification device having displacement current control and method thereof

• US 6,229,442 B1
• Filed: 03/14/2000
• Issued: 05/08/2001
• Est. Priority Date: 03/14/2000
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Kakkanad, Sebastian T., Quaderer, James G., Rolin, John Howard
• Primary Examiner(s): Hofsass, Jeffery
• Assistant Examiner(s): LA, ANH V
• Application Number:
  US09/525,718
• Time in Patent Office: 420 Days
• Field of Search: 340/572.1, 340/572.2, 340/572.3, 340/572.4, 340/572.5, 340/572.6, 340/572.7, 340/572.8, 340/572.9, 455/78, 455/193.1, 455/271, 455/284, 343/893, 343/872, 343/845, 343/700 MS, 235/439, 235/487, 342/51
• US Class Current: 340/572.1
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22

Abstract

A radio frequency identification (RFID) device (12) having displacement current control. The RFID device (12) comprises a voltage source (30), and exciter electrode, electronic circuitry, a displacement current control surface (74) and a dielectric. The voltage source has a current return node. The exciter electrode is coupled to the voltage source. The displacement current control surface (74) is placed between the exciter electrode and the electronic circuitry. The dielectric is positioned between the displacement current control surface and the electronic circuitry, wherein the displacement current control surface is electrically terminated to the current return node of the voltage source.

Claims

1. A radio frequency identification (RFID) device having displacement current control, the RFID device comprising:

a voltage source having a current return node;

an exciter electrode coupled to the voltage source;

the RFID device having electronic circuitry;

a displacement current control surface (DCCS) placed between the exciter electrode and the electronic circuitry; and

a dielectric between the DCCS and the electronic circuitry, wherein the DCCS is electrically terminated to the current return node of the voltage source.

2. The RFID device of claim 1 further comprising a conducting surface placed between the DCCS and the electronic circuitry, wherein the conducting surface is used as a voltage reference for the electronic circuitry.

3. The RFID device of claim 1 wherein the DCCS uses conductive materials selected from a group consisting of:

metal sheet, foil, film, ink, paint, and loaded plastic.

4. The RFID device of claim 1 wherein the DCCS is substantially flat.

5. The RFID device of claim 1 wherein the DCCS is three-dimensional.

6. The RFID device of claim 1 wherein the electronic circuitry is assembled onto a substrate selected from a group consisting of:

printed circuit board, polymers, dielectric, paper, glass, epoxy, and semiconductor material.

7. The RFID device of claim 6 wherein the DCCS is integrated into the substrate.

8. The RFID device of claim 6 wherein the DCCS and a conductive surface is integrated into the substrate.

9. A radio frequency identification (RFID) device having displacement current control, the RFID device comprising:

a conductive material having a first impedance;

the RFID device having electronic circuitry; and

an exciter element having a second impedance, wherein the second impedance is greater than the first impedance, and wherein the exciter element generates a current that is partially diverted by the conductive material,

wherein the conductive material, electronic circuitry, and the exciter element are connected via a common impedance path.

10. The RFID device of claim 9 wherein the conductive material is positioned in close proximity to the electronic circuitry.

11. The RFID device of claim 9 wherein the electronic circuitry is assembled onto a substrate selected from a group consisting of:

printed circuit board, polymers, dielectric, paper, glass, epoxy, and semiconductor material.

12. The RFID device of claim 11 wherein the conductive material is positioned on the substrate.

13. The RFID device of claim 11 wherein the conductive material is manufactured within the substrate.

14. The RFID device of claim 9 wherein the exciter element is external to the electric field RFID device.

15. A method of controlling displacement current in a radio frequency identification (RFID) device, the method comprising the steps of:

providing an exciter electrode;

providing electronic circuitry;

positioning a displacement current control surface (DCCS) placed between the exciter electrode and the electronic circuitry; and

providing a dielectric between the DCCS and the electronic circuitry, wherein the DCCS is electrically terminated to a current return node of a voltage source used to generate an electric field.

16. The method of claim 15 further comprising utilizing a capacitance formed between the exciter electrode and the DCCS as a circuit element.

17. The method of claim 15 further comprising positioning the electronic circuitry away from an edge of the RFID device.

18. The method of claim 15 further comprising positioning the electronic circuitry in close proximity to the DCCS.

19. The method of claim 15 further comprising extending at least one dimension of the DCCS beyond a boundary formed by the exciter electrode and the electronic circuitry.

20. The method of claim 15 further comprising extending at least one dimension of the DCCS and the electronic circuitry beyond a boundary formed by the exciter electrode.

21. The method of claim 15 further comprising reducing at least one dimension of the exciter electrode to be within a boundary formed by the DCCS and the electronic circuitry.