METHOD AND SYSTEM OF DETERMINING A LOCATION CHARACTERISTIC OF A RFID TAG

• US 20090002165A1
• Filed: 06/28/2007
• Published: 01/01/2009
• Est. Priority Date: 06/28/2007
• Status: Abandoned Application

• Current Assignee: Round Rock Research LLC
• Original Assignee: Micron Technology, Inc.
• Inventors: Tuttle, John R
• Application Number:
  US11/769,953
• Publication Number:
  US 20090002165A1
• Time in Patent Office: Days
• US Class Current: 340/572.100
• CPC Class Codes: G01S 3/48 the waves arriving at the antennas being continuous or intermittent and the phase difference of signals derived therefrom being measured
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G06K 7/10346 the antenna being of the far field type, e.g. HF types or dipoles
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: G08B 13/2471 Antenna signal processing by receiver or emitter
• CPC Class Codes: G08B 13/2474 Antenna or antenna activator geometry, arrangement or layout loop antennae H01Q1/22

Abstract

Method and system of determining a locational characteristic of a RFID tag. At least some of the illustrative embodiments are systems comprising a radio frequency identification (RFID) reader, and a phased-array reading antenna coupled to the RFID reader (the phased-array reading antenna comprising a plurality of antenna elements). The system is configured to determine a value indicative of direction of a RFID tag relative to the phased-array reading antenna based on an analysis of phase of signals induced on each of the antenna elements of the phased-array antenna by a return signal from the RFID tag.

Claims

1. A system comprising:

a radio frequency identification (RFID) reader; and

a phased-array reading antenna coupled to the RFID reader, the phased-array reading antenna comprising a plurality of antenna elements;

wherein the system is configured to determine a value indicative of direction of a RFID tag relative to the phased-array reading antenna based on an analysis of phase of signals induced on each of the antenna elements of the phased-array antenna by a return signal from the RFID tag.

2. The system according to claim 1 further comprising a location circuit, wherein the location system coupled to the phased-array antenna, wherein the location system is configured to determine the value indicative of direction of a RFID tag relative to the phased-array reading antenna.

3. The system according to claim 1 wherein the system is configured to determine a value indicative of distance from the phased-array reading antenna to the RFID tag based on a return signal strength indication (RSSI) of at least one of the signals induced on an antenna element.

4. The system according to claim 3 wherein the system is configured to determine the value indicative of distance based on RSSI of the signals induced on each of the antenna elements.

5. The system according to claim 1 further comprising:

wherein, for a plurality of phase delay values, the system is configured to apply an integer multiple of the phase delay value to the signal induced on each of the antenna elements to produce delayed signals, and to combine the delayed signals to produce a combined signal;

wherein the system is configured to determine the value indicative of direction based on a characteristic of the combined signal.

6. The system according to claim 5 wherein the system is configured to determine the value indicative of direction based on at least one selected from the group consisting of:

a phase delay value where an amplitude of the combined signal is substantially a minimum; and

a phase delay value where an amplitude of the combined signal is substantially a maximum.

7. The system according to claim 5 wherein the system determines the value indicative of direction of the RFID tag by a lookup table that correlates phase delay values to direction of the RFID tag.

8. The system according to claim 1 wherein the phased-array antenna further comprises:

each antenna element having a reception pattern with a main lobe defining an axis;

wherein the axes are substantially parallel.

9. The system according to claim 8 wherein the axes are all co-planar.

10. The system according to claim 1 wherein the phased-array antenna further comprises:

each antenna element having a reception pattern with a main lobe defining an axis;

wherein the axes are non-parallel.

11. A method comprising:

receiving at a phased-array antenna an electromagnetic wave transmitted by a radio frequency identification (RFID) tag; and

analyzing phase of signals induced on each element of the phased-array antenna to determine a direction of the RFID tag relative to the phased-array antenna.

12. The method according to claim 11 wherein receiving further comprises receiving a backscattered electromagnetic wave from the RFID tag.

13. The method according to claim 11 wherein receiving further comprises receiving the electromagnetic wave generated from power provided by a battery of the RFID tag.

14. The method according to claim 11 further comprising determining a value indicative of distance from the phased-array antenna to the RFID tag based on a return signal strength indication (RSSI) from at least one antenna element of the phased-array antenna.

15. The method according to claim 11 wherein analyzing phase further comprises:

for a plurality of phase delay values;

applying an integer multiple of the phase delay value to the signal induced on each of the antenna elements to produce delayed signals; and

combining the delayed signals to produce a combined signal for each phase delay value;

analyzing characteristics of the combined signals to determine the direction of the RFID tag.

16. The method according to claim 15 wherein analyzing further comprising determining a phase delay value indicative of direction based on amplitude of the combined signal.

17. The method according to claim 11 wherein receiving the electromagnetic wave further comprises receiving by way of a one-dimensional phased-array antenna.

18. The method according to claim 11 wherein receiving the electromagnetic wave further comprises receiving by way of a two-dimensional phased-array antenna.

19. A system comprising:

a means for receiving an electromagnetic wave transmitted by a radio frequency identification (RFID) tag and producing a plurality of electrical signals based on the electromagnetic wave;

a means for analyzing the plurality of signals to determine a direction of the RFID tag relative to the means for receiving.

20. The system according to claim 19 further comprising a means for determining a value indicative of distance from the RFID tag to the means for receiving.

21. The system according to claim 19 wherein the means for analyzing further comprises:

a means for selectively phase delaying each of the plurality of electrical signals to create a plurality of delayed signals;

a means for combining the plurality of delayed signals to created a combined signal; and

a means for comparing a plurality of combined signals.