SYSTEM AND METHOD FOR WIRELESS COMMUNICATIONS

• US 20120182129A1
• Filed: 03/28/2012
• Published: 07/19/2012
• Est. Priority Date: 06/06/2008
• Status: Active Grant

• Current Assignee: Lyngsoe Systems
• Original Assignee: Lyngsoe Systems
• Inventors: Eggers, Patrick Claus Friedrich, Yanakiev, Boyan Radkov, Pedersen, Gert Frølund, Oprea, Alex
• Granted Patent: US 9,848,252 B2
• Time in Patent Office: Days
• US Class Current: 340/10.1
• CPC Class Codes: H04Q 2209/47 using RFID associated with sensors
• CPC Class Codes: H04Q 2209/84 Measuring functions
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

A method and system for estimating position of a moving RFID tag is provided. The method includes transmitting at least one interrogator signal; receiving, at an interrogator antenna, a reflected signal from the RFID tag; determining phase changes of the reflected signal with respect to the phase of the at least one interrogator signal; weighting the phase changes based on instant power corresponding to the phase changes; producing a phase trajectory for the reflected signal based on the weighted phase changes; and estimating position of the RFID tag relative to the interrogator antenna based on the peak of the phase trajectory for the reflected signal.

Claims

1. A method of estimating position of a moving RFID tag, comprising:

transmitting at least one interrogator signal;

receiving, at an interrogator antenna, a reflected signal from the RFID tag;

determining phase changes of the reflected signal with respect to the phase of the at least one interrogator signal;

weighting the phase changes based on instant power corresponding to the phase changes;

producing a phase trajectory for the reflected signal based on the weighted phase changes; and

estimating position of the RFID tag relative to the interrogator antenna based on the peak of the phase trajectory for the reflected signal.

2. The method of claim 1, wherein the RFID tag is closest to the interrogator antenna when the phase of a reflected signal corresponds to the peak of the phase trajectory.

3. The method of claim 1, wherein weighting the phase changes based on a comparison of instant power corresponding to the phase changes comprises comparing instant power corresponding to a phase change to instant power corresponding to at least one other phase change.

4. The method of claim 1, further comprising:

receiving, at at least one additional interrogator antenna, a reflected signal from the RFID tag;

wherein producing the phase trajectory is based the phase changes and corresponding instant power from the reflected signal received at the at least one additional interrogator antenna.

5. The method of claim 1, wherein weighting the phase changes based on instant power comprises according a relatively low weighting in the event that instant power corresponding to the phase change is relatively low compared to instant power corresponding to other phase changes.

6. The method of claim 1, wherein the interrogator antenna receives a plurality of reflected signals from the RFID tag.

7. The method of claim 1, wherein the interrogator antenna receives reflected signals from a plurality of RFID tags.

8. The method of claim 4, wherein the at least one additional interrogator antenna receives a plurality of reflected signals from the RFID tag.

9. The method of claim 4, wherein the at least one additional interrogator antenna receives reflected signals from a plurality of RFID tags.

10. A system for estimating position of a moving RFID tag, comprising:

a transmitter for transmitting at least one interrogator signal;

a receiver in communication with at least one interrogator antenna receiving a reflected signal from the RFID tag;

a phase detector determining phase changes of the reflected signal with respect to the phase of the at least one interrogator signal;

a power detector determining instant power of the reflected signal corresponding to the phase changes;

a phase peak estimator weighting the phase changes based on instant power and producing a phase trajectory for the reflected signal based on the weighted phase changes; and

a position estimator estimating position of the RFID tag relative to the at least one interrogator antenna based on the peak of the phase trajectory.

11. The system of claim 10, wherein the position estimator indicates that RFID tag is closest to the interrogator antenna when the phase of a reflected signal corresponds to the peak of the phase trajectory.

12. The system of claim 10, wherein weighting the phase changes based on a comparison of instant power corresponding to the phase changes comprises comparing instant power corresponding to a phase change to instant power corresponding to at least one other phase change.

13. The system of claim 10, wherein:

the phase detector and the power detector determine phase change and instant power, respectively, from reflected signals received from the RFID tag at at least one additional interrogator antenna;

wherein determining the phase trajectory by the phase peak estimator is based on the phase changes and corresponding instant power from the reflected signal received at the at least one additional interrogator antenna.

14. The system of claim 10, wherein weighting by the phase peak estimator based on instant power comprises according a relatively low weighting in the event that instant power corresponding to the phase change is relatively low compared to instant power corresponding to other phase changes.

15. The method of claim 10, wherein the interrogator antenna receives a plurality of reflected signals from the RFID tag.

16. The method of claim 10, wherein the interrogator antenna receives reflected signals from a plurality of RFID tags.

17. The method of claim 13, wherein the at least one additional interrogator antenna receives a plurality of reflected signals from the RFID tag.

18. The method of claim 13, wherein the at least one additional interrogator antenna receives reflected signals from a plurality of RFID tags.