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

• US 20090091454A1
• Filed: 10/04/2007
• Published: 04/09/2009
• Est. Priority Date: 10/04/2007
• Status: Active Grant

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Tuttle, John R.
• Granted Patent: US 7,932,814 B2
• Time in Patent Office: Days
• US Class Current: 340/572.7
• CPC Class Codes: G01S 11/10 using Doppler effect

Abstract

A method and system to determine physical parameters as between a 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 comprising:

generating an antenna feed signal;

a first electromagnetic wave to a radio frequency device, the transmitting 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, at least in part, on the combined signal.

2. The method as defined in claim 1 wherein transmitting further comprises transmitting to a radio frequency identification (RFID) tag.

3. The method as defined in claim 1 wherein calculating further comprises calculating the combined signal by at least one selected from the group consisting of:

summing the antenna feed signal and the received signal;

mixing the antenna feed signal with the received signal;

performing an exclusive-OR using at least portions of the antenna feed signal and the received signal.

4. The method as defined in claim 1 wherein determining further comprises determining inflection points of the sum signal.

5. The method as defined in claim 4 wherein determining the inflection points further comprises finding within the combined signal at least one selected from the group consisting of:

a null;

minima; and

maxima.

6. The method as defined in claim 1 wherein determining the relative velocity further comprises determining a number of inflection points in the combined signal over a predetermined period.

7. The method as defined in claim 1 wherein the determining the relative velocity further comprises at least one selected from the group consisting of:

determining the velocity of the RFID tag relative to a moving reading antenna; and

determining the velocity of the reading antenna relative to a moving RFID tag.

8. A system comprising:

a radio frequency identification (RFID) tag;

a reading antenna in operational relationship to the RFID tag; and

a reader circuit coupled to the reading antenna, the reader circuit configured to transmit a first electromagnetic wave to the RFID tag, the first electromagnetic wave based on an antenna feed signal;

wherein the reader circuit is configured to receive a received signal, the received signal based on a backscattered electromagnetic wave received from the RFID tag; and

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

9. The system as defined in claim 8 wherein the system is configured to determine relative velocity based on inflection points of the combined signal.

10. The system as defined in claim 9 wherein the system further is configured to determine inflection points within the sum signal being at least one selected from group consisting of:

nulls;

maxima; and

minima.

11. The system as defined in claim 8 wherein the system is configured to create the combined signal by at least one selected from the group consisting of:

a sum of the antenna feed signal and the received signal;

a multiplication of the antenna feed signal with the received signal;

performance of an exclusive-OR using at least portions of the antenna feed signal and the received signal.

12. The system as defined in claim 8 wherein the system is further configured to determine at least one selected from the group consisting of:

relative position;

acceleration; and

jerk.

13. The system as defined in claim 8 wherein the RFID tag further comprises at least one selected from the group consisting of:

a passive tag; and

semi-active tag.

14. A radio frequency identification (RFID) reader comprising:

a reading antenna configured to receive backscattered electromagnetic waves from a RFID tag to create received signals;

a reader circuit coupled to the reading antenna, the reader circuit configured to transmit an interrogating electromagnetic wave to the RFID tag, the interrogating electromagnetic wave based on an antenna feed signal;

wherein the reader circuit configured to determine relative velocity between the RFID tag and the reading antenna based on a combined signal being the combination of the antenna feed signal and the received signal.

15. The radio frequency identification reader as defined in claim 14 wherein the reader circuit is configured to determine inflection points of the combined signal.

16. The radio frequency identification reader as defined in claim 15 wherein the reader circuit is configured to determine inflection points within the sum signal being at least one selected from the group consisting of:

nulls;

maxima; and

minima.

17. The radio frequency identification reader as defined in claim 14 wherein the reader circuit is configured to determine the relative velocity based on a number of inflection points in the sum signal over a predetermined period.

18. The radio frequency identification reader as defined in claim 14 wherein the reader circuit is configured to determine at least one selected from the group consisting of:

relative position;

acceleration; and

jerk.

19. A computer-readable medium storing a program that, when executed by a processor, causes the processor to:

cause an antenna feed signal to be applied to a reading antenna to create an interrogating electromagnetic wave;

receive a received signal based on a backscattered electromagnetic wave received from the RFID tag;

calculate a combination signal being the combination of the antenna feed signal and the received signal;

determine relative velocity between the RFID tag and the reading antenna based, at least in part, on the combination signal.

20. The computer-readable medium as defined in claim 19 wherein when the processor determines, the program causes the processor to determine inflection points of the combination signal.

21. The computer-readable medium as defined in claim 20 wherein when the processor determines the inflection points, the program causes the processor to find within the sum signal at least one selected from the group consisting of:

nulls;

minima; and

maxima.

22. The computer-readable medium as defined in claim 19 wherein when the processor determines the relative velocity, the program causes the processor to determine a number of inflection points in the sum signal over a predetermined period of time.

23. The computer-readable medium as defined in claim 19 wherein when the processor determines the relative velocity, the program causes the processor to determine at least one selected from the group consisting of:

the velocity of the RFID tag relative to a moving reading antenna; and

the velocity of the reading antenna relative to a moving RFID tag.

24. The computer-readable medium as defined in claim 19 wherein when the processor determines, the program causes the processor to determine at least one selected from the group consisting of:

relative position;

acceleration; and

jerk.