Method and System to Determine Physical Parameters as Between an RFID Tag and a Reader

• US 20090091428A1
• Filed: 03/07/2008
• Published: 04/09/2009
• Est. Priority Date: 10/04/2007
• Status: Active Grant

• Current Assignee: Round Rock Research LLC
• Original Assignee: Keystone Technology Solutions, LLC
• Inventors: Tuttle, John R.
• Granted Patent: US 7,944,356 B2
• Time in Patent Office: Days
• US Class Current: 340/10.2
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal

Abstract

A method and system to determine physical parameters as between an RFID tag and a reader. At least some of the illustrative embodiments are methods comprising generating an antenna feed signal, and transmitting a first electromagnetic wave to a radio frequency device (by coupling the antenna feed signal to a reading antenna), receiving a backscattered electromagnetic wave from the radio frequency device to create a received signal, calculating a combined signal based on the antenna feed signal and received signal, and determining relative velocity between the radio frequency device and the reading antenna based on the combined signal.

Claims

1. A method implemented in a radio frequency identification (RFID) system, the method comprising:

an RFID reader generating an antenna feed signal and transmitting a first electromagnetic wave to an RFID tag according to the antenna feed signal;

the RFID reader receiving a backscattered electromagnetic wave from the RFID device to create a received signal;

generating a combined signal based on the antenna feed signal and the received signal; and

determining a relative velocity between the RFID tag and the RFID reader based, at least in part, on the combined signal.

2. The method of claim 1, wherein the backscattered electromagnetic wave is received during the RFID reader interrogating the RFID tag using the antenna feed signal.

3. The method of claim 1, wherein the generating of the combined signal comprises summing the antenna feed signal and the received signal, mixing the antenna feed signal with the received signal, or performing an exclusive-OR using at least portions of the antenna feed signal and the received signal.

4. The method of claim 3, wherein the determining of the relative velocity comprises detecting inflection points of the combined signal.

5. The method of claim 4, wherein the inflection points include one or more of null, minima, and maxima.

6. The method of claim 3, wherein determining of the relative velocity further comprises determining a time period of the inflection points.

7. The method of claim 1, wherein the backscattered electromagnetic wave is generated by the RFID tag in response to a command from the RFID reader.

8. The method of claim 7, wherein the RFID tag is instructed by the command to be in a reflective state to generate the backscattered electromagnetic wave without associated data.

9. A system comprising:

a radio frequency identification (RFID) tag;

a reading antenna; and

a reader circuit coupled to the reading antenna to transmit a first electromagnetic wave to the RFID tag, based on an antenna feed signal, and to receive a received signal based on a backscattered electromagnetic wave from the RFID tag;

wherein the system is to determine a relative velocity between the RFID tag and the reading antenna based on a combined signal of the antenna feed signal and the received signal.

10. The system of claim 9, wherein the system is to count inflection points in the combined signal to determine the relative velocity.

11. The system of claim 10, wherein the inflection points includes at least null points, maximum points, or minimum points in an envelop signal of the combined signal.

12. The system of claim 9, wherein the combined signal is a sum of the antenna feed signal and the received signal, a multiplication of the antenna feed signal with the received signal, or a result of an exclusive-OR applied on at least portions of the antenna feed signal and the received signal.

13. The system of claim 9, wherein the reader circuit is to determine an identification data stored on the RFID tag and to instruct the tag to be in a reflective state to generate the backscattered electromagnetic wave without data.

14. The system of claim 9, wherein the RFID tag comprises a passive tag or a semi-active tag.

15. A radio frequency identification (RFID) reader, comprising:

a reading antenna;

a reader circuit coupled to the reading antenna to receive a backscattered electromagnetic wave from an RFID tag to create a received signal, the reader circuit to generate an antenna feed signal corresponding to the backscattered electromagnetic wave, the reader circuit to determine a relative velocity between the RFID tag and the RFID reader based on a combined signal of the antenna feed signal and the received signal.

16. The radio frequency identification reader of claim 15, wherein the reader circuit is to detect characteristic points of the combined signal to determine the relative velocity.

17. The radio frequency identification reader of claim 16, wherein the characteristic points are null points, minimum points or maximum points.

18. The radio frequency identification reader of claim 16, wherein the reader circuit is to determine an elapse time between two characteristic points of the combined signal to determine the relative velocity.

19. The radio frequency identification reader of claim 18, wherein the combined signal comprises an envelop signal of a sum of the antenna feed signal and the received signal, a multiplication of the antenna feed signal with the received signal, or a result of an exclusive-OR applied on at least portions of the antenna feed signal and the received signal.

20. A computer-readable medium storing a program that, when executed by a radio frequency identification (RFID) system, causes the system to:

generate an antenna feed signal and transmit a first electromagnetic wave from an RFID reader to an RFID tag according to the antenna feed signal;

receive a backscattered electromagnetic wave from the RFID device to create a received signal;

generate a combined signal based on the antenna feed signal and the received signal; and

determine a relative velocity between the RFID tag and the RFID reader based, at least in part, on the combined signal.