RFID radiation nullifier

• US 20060208895A1
• Filed: 03/04/2005
• Published: 09/21/2006
• Est. Priority Date: 03/04/2005
• Status: Active Grant

• Current Assignee: Printronix
• Original Assignee: Printronix
• Inventors: Chiu, Lihu M.
• Granted Patent: US 7,268,686 B2
• Time in Patent Office: Days
• US Class Current: 340/572.700
• 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 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
• CPC Class Codes: G06K 7/10336 the antenna being of the near field type, inductive coil

Abstract

In one embodiment, a system for communicating with an RFID tag is provided that includes: a capacitive encoder adapted for placement in proximity of the RFID tag and operable to transmit a first operating signal to the RFID tag for communicating with the RFID tag; wherein the capacitive encoder is further operable to transmit to the RFID tag a second operating signal adapted to excite the RFID tag such that RF radiations from the RFID tag to adjacent RFID tags are nullified.

Claims

1. A system for communicating with an RFID tag, the system comprising:

a capacitive encoder adapted for placement in proximity of the RFID tag and operable to transmit a first operating signal to the RFID tag for communicating with the RFID tag;

wherein the capacitive encoder is further operable to transmit to the RFID tag a second operating signal adapted to excite the RFID tag such that RF radiations from the RFID tag to adjacent RFID tags are nullified.

2. The system as defined in claim 1, wherein the RFID tag comprises a tag antenna and wherein the first radiation emission is emitted by the tag antenna.

3. The system as defined in claim 2, wherein the RFID tag further comprises a transponder and wherein the first operating signal excites the transponder.

4. The system as defined in claim 1, further comprising:

a first conductive element; and

a second conductive element;

wherein the first operating signal comprises a first RF signal driven on the first conductive element and a second RF signal driven on the second conductive element, wherein the second RF signal is out of phase with the first RF signal by a predetermined phase.

5. The system as defined in claim 4, further comprising:

a third conductive element; and

a fourth conductive element, wherein the second operating signal comprises a third RF signal driven on the third conductive element and a fourth RF signal driven on the fourth conductive element.

6. The system as defined in claim 5, further comprising:

a first programmable attenuator;

a second programmable attenuator;

a first programmable phase shifter;

a second programmable phase shifter, wherein the capacitive encoder controls the first programmable attenuator and phase shifter to attenuate and phase shift an RF source to provide the third RF signal, and wherein the capacitive encoder controls the second programmable attenuator and phase shifter to attenuate and phase shift the RF source to provide the fourth RF signal.

7. The system as defined in claim 6, further comprising:

a third programmable phase shifter, wherein the capacitive encoder controls the third programmable phase shifter to phase shift the RF source by the predetermined phase to provide the second RF signal.

8. The system as defined in claim 6, further comprising:

a dielectric substrate, wherein the first, second, third, and fourth conductive elements each comprise a metallic patch on a surface of the dielectric substrate; and

a bus structure formed within the dielectric substrate and adapted to carry the first, second, third, and fourth RF signals to each of the metallic patches.

9. The system as defined in claim 8, further comprising:

a plurality of metallic patches formed on the surface of the dielectric substrate, wherein the capacitive encoder is operable to select the first, second, third, and fourth metallic patches from the plurality of metallic patches.

10. A method for communicating with an RFID tag, the method comprising:

placing a capacitive encoder in proximity of the RFID tag;

transmitting a first operating signal from the capacitive encoder to the RFID tag for communicating with the RFID tag; and

during the transmission of the first operating signal, transmitting to the RFID tag a second operating signal from the capacitive encoder such that RF transmission from the RFID tag to adjacent RFID tags is nullified.

11. The method as defined in claim 10, wherein the RFID tag comprises a tag antenna and wherein the first radiation emission is emitted by the tag antenna.

12. The method as defined in claim 10, wherein the RFID tag further comprises a transponder and wherein the first operating signal excites the transponder.

13. The method as defined in claim 10, wherein transmitting a first operating signal from the capacitive encoder comprises transmitting a first RF signal from a first conductive element and transmitting a second RF signal from a second conductive element, wherein the second RF signal is out of phase from the first RF signal by a predetermined phase.

14. The method as defined in claim 13, further comprising:

modeling an antenna of the RFID tag to determine at least one nullifying phase shift and at least one nullifying attenuation;

phase shifting and attenuating an RF source according to the at least one nullifying phase shift and attenuation to provide a third and a fourth RF signal, wherein transmitting to the RFID tag a second operating signal comprises transmitting the third RF signal from a third conductive element and transmitting the fourth RF signal from the fourth conductive element.