Object localization with RFID infrastructure

• US 9,977,112 B2
• Filed: 09/23/2011
• Issued: 05/22/2018
• Est. Priority Date: 09/27/2010
• Status: Active Grant

• Current Assignee: University of Virginia
• Original Assignee: University of Virginia Patent Foundation (University of Virginia)
• Inventors: Chawla, Kirti, Robins, Gabriel
• Primary Examiner(s): Adams, Tashiana R
• Assistant Examiner(s): Seraydaryan, Helena H
• Application Number:
  US13/876,078
• Publication Number:
  US 20130181869A1
• Time in Patent Office: 2,433 Days
• Field of Search: 342458
• CPC Class Codes: G01S 13/758 using a signal generator powered by the interrogation signal
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 5/0295 Proximity-based methods, e.g. position inferred from reception of particular signals
• CPC Class Codes: G01S 7/4013 involving adjustment of the transmitted power
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions

Abstract

Object localization with an radio-frequency identification (RFID) infrastructure is described. A plurality of transmission power levels established by an RFID reader can be searched to determine a measurement power level corresponding to a target. A region that includes the target can then be determined using information about a physical relationship between the RFID reader and a reference location via correlating the measurement power level to a reference power level corresponding to the reference location.

Claims

1. A system comprising:

a search circuit configured to search a plurality of transmission power levels established by a radio-frequency identification (RFID) reader, the search circuit configured to determine a measurement power level corresponding to a target, wherein to search the plurality of transmission power levels the search circuit uses at least one of a linear search or a binary search, wherein the linear search uses variable power step sizes to establish a fixed number of intervals within a variable power range, and wherein the binary search halves step sizes during each iteration of the search; and

a target localization circuit configured to;

select a reference location from a plurality of reference locations via determining a greater affinity between the measurement power level and a reference power level corresponding to a reference location than between the measurement power level and other reference power levels corresponding to other respective reference locations; and

determine a region that includes the target using information about a physical relationship between the RFID reader and the reference location via correlating the measurement power level to the reference power level, wherein the physical relationship between the RFID reader and the reference location is fixed with respect to the reference power level that was previously established via interrogation of the reference location by the RFID reader at a fixed position, and wherein the affinity between the measurement power level and the reference power level is determined by a heuristic selected from a group of heuristics that includes;

2. The system of claim 1, wherein the measurement power level is a transmission power level established by the RFID reader to interrogate the target at or near a limit of the target'"'"'s sensitivity.

3. The system of claim 1, wherein the search circuit is configured to first use the binary search to converge on a transmission power range and then use the linear search with a step size adjusted to the transmission power range from the binary search to determine the measurement power level.

4. The system of claim 1, wherein the localization circuit is configured to determine a refined region that includes the target using information about two or more regions established using respective measurement power levels determined corresponding to respective RFID readers.

5. The system of claim 1, further comprising a reference power calibration circuit configured to search the plurality of transmission power levels for the reference power level, the reference power level being a transmission power level established by the RFID reader to interrogate the reference location at or near the limit of the references location'"'"'s sensitivity.

6. The system of claim 1, further comprising a sorting circuit configured to classify a plurality of RFID tags into one or more categories, wherein the localization circuit is configured to determine the region that includes the target using information about the physical relationship between the RFID reader and the reference location, and information about a classification of one or more of an RFID tag located at or near the target, or an RFID tag located at or near the reference location.

7. The system of claim 6, wherein the target and reference location comprise respective RFID tags comprising the same category of sensitivity range.

8. A method comprising:

searching a plurality of transmission power levels established by a radio-frequency identification (RFID) reader to determine a measurement power level corresponding to a target, wherein searching the plurality of transmission power levels includes using at least one of a linear search or a binary search, wherein the linear search uses variable power step sizes to establish a fixed number of intervals within a variable power range, and wherein the binary search halves step sizes during each iteration of the search; and

determining a region that includes the target using information about a physical relationship between the RFID reader and a reference location via correlating the measurement power level to a reference power level corresponding to the reference location, wherein the physical relationship between the RFID reader and the reference location is fixed with respect to the reference power level that was previously established via interrogation of the reference location by the RFID reader at a fixed position, wherein the reference location is selected from a plurality of reference locations via determining a greater affinity between the measurement power level and the reference power level than between the measurement power level and other reference power levels corresponding to other respective reference locations, and wherein the affinity between the measurement power level and the reference power level is determined by a heuristic selected from a group of heuristics that includes;

9. The method of claim 8, wherein the measurement power level is a transmission power level established by the RFID reader to interrogate the target at or near a limit of the target'"'"'s sensitivity.

10. The method of claim 8, wherein searching the plurality of transmission points includes first using the binary search to converge on a transmission power range and then linearly searching with a step size adjusted to the transmission power range from the binary search to determine the measurement power level.

11. The method of claim 8, comprising determining a refined region that includes the target using information about two or more regions established using respective measurement power levels determined corresponding to respective RFID readers.

12. The method of claim 8, comprising periodically calibrating the reference power level by searching the plurality of transmission power levels for the reference power level, the reference power level being a transmission power level established by the RFID reader to interrogate the reference location at or near the reference location'"'"'s sensitivity.

13. The method of claim 8, comprising sorting a plurality of RFID tags into one or more categories, wherein determining the region includes using information about a categorization of one or more of an RFID tag located at or near the target or an RFID tag located at or near the reference location.

14. The method of claim 13, wherein the target and reference locations comprise respective RFID tags comprising the same category of sensitivity range.

15. At least one non-transitory machine readable medium including instructions, which when executed by a machine, cause the machine to perform operations comprising:

searching a plurality of transmission power levels established by a radio-frequency identification (RFID) reader to determine a measurement power level corresponding to a target, wherein searching the plurality of transmission power levels includes using at least one of a linear search or a binary search, wherein the linear search uses variable power step sizes to establish a fixed number of intervals within a variable power range, and wherein the binary search halves step sizes during each iteration of the search; and

determining a region that includes the target using information about a physical relationship between the RFID reader and a reference location via correlating the measurement power level to a reference power level corresponding to the reference location, wherein the physical relationship between the RFID reader and the reference location is fixed with respect to the reference power level that was previously established via interrogation of the reference location by the RFID reader at a fixed position, wherein the reference location is selected from a plurality of reference locations via determining a greater affinity between the measurement power level and the reference power level than between the measurement power level and other reference power levels corresponding to other respective reference locations, and wherein the affinity between the measurement power level and the reference power level is determined by a heuristic selected from a group of heuristics that includes;

16. The machine readable medium of claim 15, wherein the measurement power level is a transmission power level established by the RFID reader to interrogate the target at or near a limit of the target'"'"'s sensitivity.

17. The machine readable medium of claim 15, machine readable medium searching the plurality of transmission points includes first using the binary search to converge on a transmission power range and then linearly searching with a step size adjusted to the transmission power range from the binary search to determine the measurement power level.

18. The machine readable medium of claim 15, wherein the operations comprise determining a refined region that includes the target using information about two or more regions established using respective measurement power levels determined corresponding to respective RFID readers.

19. The machine readable medium of claim 15, wherein the operations comprise periodically calibrating the reference power level by searching the plurality of transmission power levels for the reference power level, the reference power level being a transmission power level established by the RFID reader to interrogate the reference location at or near the reference location'"'"'s sensitivity.

20. The machine readable medium of claim 15, wherein the operations comprise sorting a plurality of RFID tags into one or more categories, wherein determining the region includes using information about a categorization of one or more of an RFID tag located at or near the target or an RFID tag located at or near the reference location.

21. The machine readable medium of claim 20, wherein the target and reference locations comprise respective RFID tags comprising the same category of sensitivity range.