Method and system to determine physical parameters as between a RFID tag and a reader

• US 7,932,814 B2
• Filed: 10/04/2007
• Issued: 04/26/2011
• Est. Priority Date: 10/04/2007
• Status: Expired due to Fees

• Current Assignee: Round Rock Research LLC
• Original Assignee: Round Rock Research LLC
• Inventors: Tuttle, John R
• Primary Examiner(s): Bugg; George A
• Assistant Examiner(s): MCNALLY, KERRI L
• Application Number:
  US11/867,273
• Publication Number:
  US 20090091454A1
• Time in Patent Office: 1,300 Days
• Field of Search: 340/10.3, 340/572.1, 340/568.1, 340/568.5, 340/568.6, 340/568.7, 340/568.8, 340/571, 340/10.1, 340/10.4
• US Class Current: 340/10.4
• 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;

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, wherein the combined signal includes a plurality of inflection points, each inflection point corresponding to a different position of the radio frequency device relative to the reading antenna, wherein the plurality of inflection points comprises a first inflection point, a last inflection point, and at least one intermediate inflection point between the first inflection point and the last inflection point; and

determining a relative velocity between the radio frequency device and the reading antenna by detecting the inflection points of the combined signal over a predetermined time period, wherein the predetermined time period begins at a time associated with the first inflection point and ends at a time associated with the last inflection point.

2. The method as defined in claim 1 wherein the radio frequency device is 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 the inflection points comprise at least one selected from the group consisting of:

a null;

minima; and

maxima.

5. 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 radio frequency device relative to a moving reading antenna; and

determining the velocity of the reading antenna relative to a moving radio frequency device.

6. The method of claim 1, wherein the first inflection point and the last inflection point each correspond to a null value.

7. 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 being based on a backscattered electromagnetic wave received from the RFID tag;

wherein the reader circuit generates a combined signal of the antenna feed signal and the received signal;

wherein the combined signal includes a plurality of inflection points, each inflection point corresponding to a different position of the RFID tag relative to the reading antenna;

wherein the plurality of inflection points comprises a first inflection point, a last inflection point, and at least one intermediate inflection point between the first inflection point and the last inflection point; and

wherein the reader circuit determines a relative velocity between the RFID tag and the reading antenna by detecting the inflection points of the combined signal over a predetermined time period, wherein the predetermined time period begins at a time associated with the first inflection point and ends at a time associated with the last inflection point.

8. The system as defined in claim 7 wherein the reader circuit determines the relative velocity by counting the inflection points of the combined signal.

9. The system as defined in claim 8 wherein the inflection points comprise at least one selected from the group consisting of:

nulls;

maxima; and

minima.

10. The system as defined in claim 7 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.

11. The system as defined in claim 7 wherein the system is further configured to determine at least one selected from the group consisting of:

relative position;

acceleration; and

jerk.

12. The system as defined in claim 7 wherein the RFID tag further comprises at least one selected from the group consisting of:

a passive tag; and

a semi-active tag.

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

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

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

wherein the reader circuit is configured 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,

wherein the combined signal includes a plurality of inflection points, each inflection point corresponding to a different position of the RFID tag relative to the reading antenna,

wherein the plurality of inflection points comprises a first inflection point, a last inflection point, and at least one intermediate inflection point between the first inflection point and the last inflection point,

wherein the reader circuit determines the relative velocity by detecting the inflection points of the combined signal over a predetermined time period, wherein the predetermined time period begins at a time associated with the first inflection point and ends at a time associated with the last inflection point.

14. The radio frequency identification reader as defined in claim 13 wherein the inflection points comprise at least one selected from the group consisting of:

nulls;

maxima; and

minima.

15. The radio frequency identification reader as defined in claim 13 wherein the reader circuit is configured to determine at least one selected from the group consisting of:

relative position;

acceleration; and

jerk.

16. A non-transitory 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 a RFID tag;

calculate a combination signal being the combination of the antenna feed signal and the received signal, wherein the combination signal includes a plurality of inflection points, each inflection point corresponding to a different position of the RFID tag relative to the RFID reader, wherein the plurality of inflection points comprises a first inflection point, a last inflection point, and at least one intermediate inflection point between the first inflection point and the last inflection point;

determine a relative velocity between the RFID tag and the reading antenna by detecting the inflection points of the combined signal over a predetermined time period, wherein the predetermined time period begins at a time associated with the first inflection point and ends at a time associated with the last inflection point.

17. The non-transitory computer-readable medium as defined in claim 16 wherein the inflection points comprise at least one selected from the group consisting of:

nulls;

minima; and

maxima.

18. The non-transitory computer-readable medium as defined in claim 16 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.

19. The non-transitory computer-readable medium as defined in claim 16 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.