Radio frequency identification tag location estimation and tracking system and method

• US 10,585,159 B2
• Filed: 02/09/2018
• Issued: 03/10/2020
• Est. Priority Date: 04/14/2008
• Status: Active Grant

• Current Assignee: Mojix Inc
• Original Assignee: Mojix Inc
• Inventors: Sadr, Ramin, Stephens, Scott, Jones, Christopher Richard
• Primary Examiner(s): Girma, Fekadeselassie
• Application Number:
  US15/893,474
• Publication Number:
  US 20190018101A1
• Time in Patent Office: 760 Days
• Field of Search: None
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 3/74 Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14
• CPC Class Codes: G01S 5/0278 involving statistical or probabilistic considerations G01S5/0252, G01S5/0294 take precedence
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• 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 7/10366 the interrogation device being adapted for miscellaneous applications

Abstract

Systems and methods for locating one or more radio frequency identification (RFID) tags are provided. A phase difference of received information signals of illuminated RFID tags is utilized to locate the RFID tags. One or more exciters transmit interrogation signals to illuminate the RFID tags in which the exciters may have a plurality of antenna selectively configured to transmit through two or more antennas and to receive on one antenna. Multiple reads of the same RFID tag can also be performed to generate a probability model of the location of the RFID tag. An enhanced particle filter is applied to probability model to determine the exact location of the RFID.

Claims

1. A method of locating one or more radio frequency identification (RFID) tags comprising:

transmitting, to at least one RFID tag, a first interrogation signal from a first transmit antenna at a first location and a different second interrogation signal from a second transmit antenna at a second location;

receiving first and second information signals at a set of one or more receive antennas in a third location in response to the first and second interrogation signals from the at least one RFID tag;

determining a set of phase differences for the received first and second information signals from the at least one RFID tag received by the at least one receive antenna;

determining, based on the set of phase differences;

a first path length between the first location of the first transmit antenna, the at least one RFID tag, and the third location of the set of receive antennas, and

a second path length between the second location of the second transmit antenna, the at least one RFID tag, and the third location of the set of receive antennas; and

identifying a location of the at least one RFID tag based on the determined phase differences of the first and second received information signals and the first and second path lengths.

14. The method of claim 1, wherein transmitting the first and second interrogation signals to the at least one RFID tag comprises activating the first and second transmit antennas to send the first and second interrogation signals simultaneously.

15. The method of claim 14, wherein identifying the location of the at least one RFID tag comprises using differences between the first and second frequencies to identify the location of the at least one RFID tag.

16. The method of claim 1, wherein identifying the location of the at least one RFID tag from the received information signals comprises using a probability model to estimate the location of the at least one RFID tag.

2. A radio frequency identification (RFID) system for locating one or more RFID tags, the system comprising:

a plurality of antennas comprising;

first and second transmit antennas configured to transmit interrogation signals to at least one RFID tag, wherein the first and second transmit antennas are at first and second locations respectively; and

at least one receive antenna to receive information signals from the at least one RFID tag; and

a reader configured to;

selectively activate the first transmit antenna to transmit a first interrogation signal at a first frequency and the second transmit antenna to transmit a second interrogation signal at a different second frequency;

receive first and second information signals in response to the first and second interrogation signals at a set of one or more receive antennas in a third location; and

identify a location of the at least one RFID tag based on the first, second, and third locations, and a first path length between the set of receive antennas, the at least one RFID tag, and the first transmit antenna, and a second path length between the set of receive antennas, the at least one RFID tag, and the second transmit antenna, wherein the path lengths are determined from the first and second information signals.

3. The system of claim 2, wherein the reader activates the first and second transmit antennas to send the first and second interrogation signals simultaneously.

4. The system of claim 3, wherein the reader identifies the location of the at least one RFID tag further based on phase differences between the first and second information signals.

5. The system of claim 2, wherein the reader identifies the location of the at least one RFID tag further based on frequency differences of the first and second information signals.

6. The system of claim 5, wherein the reader identifies the location of the at least one RFID tag based on a ratio of phase differences between the first and second information signals versus the frequency differences of the first and second information signals.

7. The system of claim 2, wherein the first and second antennas are associated with an exciter, wherein the exciter comprises at least one transmit antenna and at least one receive antenna.

8. The system of claim 7, wherein each antenna of the exciter can operate as either a transmit antenna or a receive antenna.

9. The system of claim 2, wherein the first and second transmit antennas are each associated with different exciters.

10. The system of claim 2, wherein the reader selectively activates the first and second transmit antennas in a plurality of iterations to collect a plurality of information signals from the at least one RFID tag for each iteration.

11. The system of claim 2, wherein the reader activates the first transmit antenna to use a first frequency for a first iteration and a different, third frequency for a subsequent second iteration.

12. The system of claim 2, wherein the reader estimates the location of the at least one RFID tag from the received information signals using a probability model.

13. The system of claim 12, wherein the probability model is determined using a particle filter.

17. The system of claim 3, wherein the reader is further configured to transmit a third interrogation signal using the first transmit antenna and a fourth interrogation signal using the second antenna, wherein the third interrogation signal has a same set of properties as the first interrogation signal and the fourth interrogation signal has a different set of properties from the second interrogation signal.

18. The system of claim 17, wherein the first and third interrogation signals use a same frequency and the second and fourth interrogation signals use different frequencies.

19. The system of claim 3, wherein the reader is configured to locate the RFID tag further based on differences in frequency between the received first and second information signals.