System and method for locating radio frequency identification tags

• US 6,661,335 B1
• Filed: 09/24/1999
• Issued: 12/09/2003
• Est. Priority Date: 09/24/1999
• Status: Expired due to Fees

• Current Assignee: GE Security Incorporated (Carrier Global Corporation)
• Original Assignee: GE Interlogix Incorporated (General Electric Company)
• Inventors: Seal, James
• Primary Examiner(s): Horabik, Michael
• Assistant Examiner(s): BANGACHON, WILLIAM L
• Application Number:
  US09/406,092
• Time in Patent Office: 1,537 Days
• Field of Search: 340/10.1, 340/10.33, 340/5.2, 340/5.6, 340/8, 340/5.92, 340/572.1, 340/3, 340/572.4, 340/572.7, 340/825.49, 455/502, 455/101, 343/742, 342/357.07, 342/51
• US Class Current: 340/10.1
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

A system and method for determining the position of a radio frequency identification (RFID) transponder with respect to a sensor. In one embodiment, the system comprises a plurality of stationary sensors located in an array within certain physical areas. Each sensor comprises a plurality of antenna coils arranged in unique physical orientations and capable of transmitting radio frequency signals of differing phase. The RFID transponder includes an antenna which receives the plurality of signals generated by the antenna coils, and compares the phase of at least two of the signals to determine the relative position of the transponder. In a second aspect of the invention, the aforementioned antenna coils emit two direction finding mode (DFM) signals in succession; the first signal with all antenna coils turned on, the second with one of the coils turned off. The spatial relationship of the transponder antenna and individual antenna coils precludes all of the signals in each sensor from being rejected by the transponder during emission of both the first and second DFM signal. Hence, the transponder is kept in constant communication with the sensor in all orientations. In another embodiment, the location of the transponder with respect to two or more sensor(s) is determined through measurement of the intensity of the signals received by the antenna coil of the transponder. The invention also includes a system and method for transmitting data between a sensor and a dormant (motionless) RFID transponder using a hand-held high intensity RF probe.

Claims

1. An asset management system, comprising:

a plurality of sensor arrays disposed at a plurality of different fixed locations in a building, each of said sensor arrays being capable of transmitting and receiving radio frequency signals;

at least one transponder affixed to a moveable asset requiring management, said at least one transponder being configured to receive and transmit radio frequency signals;

a processor executing a program capable of analyzing said radio frequency signals transmitted by said sensor arrays and deriving an estimate of the position of said at least one transponder in relation to each of said sensor arrays, wherein said processor and program are disposed within said at least one transponder; and

a computer in data communication with said processor such that the location of said at least one transponder may be periodically stored within said computer.

2. The system of claim 1, wherein said at least one transponder transmits said estimate to said computer via at least one of said sensor arrays.

22. The asset management system of claim 1, wherein each of said plurality of sensor arrays transmits said radio frequency signal concurrently.

3. A security system, comprising:

a controller;

at least one card reader in data communication with said controller, said at least one card reader configured for reading data from security cards; and

a plurality of transponder readers disposed at fixed locations in a building, wherein said transponder readers are in data communication with said controller, wherein the transponder readers can estimate the positions of a plurality of moveable transponders relative to said transponder readers, said positions and said data read from said security cards being used to control access to a given location;

wherein at least one of said moveable transponders comprises a processor executing a program configured for analyzing said radio frequency signals transmitted by said transponder readers and deriving an estimate of the position of said at least one moveable transponder in relation to each of said transponder readers.

4. The security system of claim 3, wherein at least one of the moveable transponders is affixed to a physical asset requiring management.

5. The security system of claim 3, wherein at least one of the moveable transponders is configured to receive and transmit radio frequency signals.

6. The security system of claim 3, wherein each of said transponder readers is disposed at a different fixed location and is configured to transmit and receive radio frequency, signals.

7. The security system of claim 6, wherein said at least one of said moveable transponders analyzes said radio frequency signals transmitted by said transponder readers in order to derive an estimate of the position of said at least one moveable transponder in relation to each of said transponder readers.

8. The security system of claim 7, further comprising a computer in data communication with said controller, said computer having at least one data storage device.

9. The security system of claim 8, wherein said at least one moveable transponder transmits said estimate to said computer via at least one of said transponder readers.

10. The security system of claim 3, further comprising a computer in data communication with said controller, said computer having at least one data storage device.

11. The security system of claim 3, wherein at least one of said transponder readers comprises a plurality of individual antenna coils.

12. The security system of claim 11, wherein each of said coils is orthogonal to each other.

13. The security system of claim 11, wherein each of said antenna coils of said at least one transponder reader transmits a signal having an electrical phase different than that of the other antenna coils.

14. The security system of claim 13, wherein said at least one transponder reader comprises three individual antenna coils, and each antenna coil transmits a signal shifted in electrical phase by 120 degrees from each of the other antenna coils.

15. The security system of claim 10, wherein said computer and said controller are at physically separate locations, and are linked by a data network.

16. The security system of claim 15, wherein said data network utilizes a packetized protocol.

17. A security system, comprising:

means for transmitting electromagnetic radiation having data associated therewith, said means for transmitting disposed at a fixed position in a building;

means for receiving said electromagnetic energy and data transmitted by said means for transmitting, said means for receiving being portable;

means for controlling said means for transmitting, said means for controlling being operatively coupled thereto;

means for reading information from a security device, said means for reading being in data communication with said means for controlling; and

means for processing, said means for processing having a computer program associated therewith and being operatively coupled to said means for receiving, said means for processing and said computer program cooperating to process said data so as to determine the position of said means for receiving with respect to said means for transmitting;

wherein said means for controlling utilizes said position and said information in order to control access.

18. A method of controlling access at a security perimeter of a building, comprising:

disposing a reader in proximity to said security perimeter of said building, said reader being capable of reading information from a first portable device;

reading information from said first portable device using said reader;

disposing a plurality of transceivers each having a plurality of antenna coils in proximity to said security perimeter of said building, said transceivers being capable of radiating electromagnetic energy;

providing a controller in data communication with said reader and said plurality of transceivers;

radiating said electromagnetic energy from each of said plurality of transceivers;

transporting a second portable device within range of i at least a portion of said plurality of transceivers, said second portable device being capable of receiving said electromagnetic energy and determining its position relative to said transceivers based thereon;

analyzing said electromagnetic energy using said second portable device and generating data relating to the position thereof;

transmitting said position data from said second portable device to at least one of said transceivers;

analyzing said position data and said information read by said reader; and

controlling access through said security perimeter of said building based on said act of analyzing.

19. The method of claim 18, further comprising the act of radiating electromagnetic energy from each of a plurality of individual antenna coils with each of said transceivers, said energy radiated from each coil of a given transceiver having a different electrical phase than the other coils/of that same transceiver.

20. The method of claim 18, wherein said first and second portable devices are the same physical device.

21. A method of controlling access at a security perimeter of a building, comprising:

obtaining identification information from a first portable device using a reader disposed at a fixed location in proximity to said perimeter;

radiating radio frequency signals of different phase to a second portable device;

deriving an estimate of the position of said second portable device based on said radio frequency signals, wherein said deriving is performed within said second portable device;

transmitting said estimate of position to a controller which controls access;

transmitting said identification information to said controller; and

a controlling access at said perimeter based on said identification information and said estimate of position.