Dual mode tracking system

• US 6,353,406 B1
• Filed: 06/24/1999
• Issued: 03/05/2002
• Est. Priority Date: 10/17/1996
• Status: Expired due to Term

• Current Assignee: RF Technologies, Inc. (Microwave Techniques LLC)
• Original Assignee: RF Technologies, Inc. (Microwave Techniques LLC)
• Inventors: Lanzl, Colin, Werb, Jay
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US09/339,740
• Time in Patent Office: 985 Days
• Field of Search: 342/42, 342/44, 342/118, 342/125, 342/126, 342/127, 342/133, 342/139, 342/140, 342/146, 340/10.1, 340/5.8, 340/573.1, 340/825.49, 340/573.4
• US Class Current: 342/118
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement
• 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: G06K 17/00 Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
• CPC Class Codes: G06K 19/0724 the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types
• 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 7/10059 transponder driven
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: G07C 9/28 the pass enabling tracking or indicating presence

Abstract

System for tracking mobile tags. Cell controllers with multiple antenna modules generate a carrier signal which is received by the tags. Tags shift the frequency of the carrier signal, modulate an identification code onto it, and transmit the resulting tag signal at randomized intervals. The antennas receive and process the response, and determine the presence of the tags by proximity and triangulation. The recursive-least squares (RLS) technique is used in filtering received signals. Distance of a tag from an antenna is calculated by measuring the round trip signal time. The cell controllers send data from the antenna to a host computer. The host computer collects the data and resolves them into positional estimates. Data are archived in a data warehouse, such as an SQL Server. Also disclosed is an article tracking system that supports both active and passive tags with a cell controller able to read both passive and active tag signals.

Claims

1. A system for locating an object associated with a tag, comprising:

a cell controller that includes a receiver for receiving a signal, the receiver having a receiving portion that receives the signal in a wireless form;

a first tag associated with said object that outputs the signal, said first tag having no active internal power source; and

an external power source that provides a wireless power source to the first tag, the external power source being physically separated from the receiving portion of the receiver so that the first tag would not be powered by the external power source if the external power source was located at the receiving portion.

2. The system of claim 1, wherein said receiving portion is an antenna.

3. The system of claim 1, wherein the first tag includes a dead battery that formerly provided an internal power source to the first tag.

4. The system of claim 1, wherein the first tag is an active tag having the internal power source removed.

5. The system of claim 1, further comprising at least one active tag associated with another object, the active tag adapted to communicate with the cell controller.

6. The system of claim 1, wherein a unique identifier is associated with said first tag, and said unique identifier is phase modulated onto said signal and used to determine the distance of said first object from a reference point.

7. The system of claim 1, wherein said cell controller includes:

a quadrature modulator that extracts inphase and quadrature components of said signal; and

a digitizer that digitizes the inphase and quadrature components for subsequent processing.

8. A method for locating an object, comprising:

receiving a wireless source of power at a first tag associated with said object, the wireless source of power being emitted from an external power source location;

sending a wireless signal from the first tag; and

receiving said wireless signal at a reception location to determine a location of the object, the reception location being separated from the external power source location so that the first tag would not be powered by the wireless source of power if the external power source location was located at the reception location.

9. The method of claim 8, further comprising:

providing a hybrid active/passive tag as the first tag.

10. The method of claim 8, further comprising:

providing a passive tag as the first tag.

11. The method of claim 10, further comprising:

providing an active tag as a second tag associated with a second object, the active tag capable of communication to identify the location of the second object.

12. The method of claim 8, wherein the step of sending the wireless signal comprises transponding a received signal.

13. The method of claim 8, further comprising:

transmitting a first signal at a transmission location;

receiving said first signal at an active tag associated with a second object; and

transponding said first signal by the active tag.

14. The method of claim 8, further comprising:

associating a unique identifier with said first tag;

phase modulating said unique identifier onto said wireless signal; and

determining the distance of said first object by measuring the round trip time associated with a first signal being sent to the first tag and said wireless signal being received.

15. The method claim 8, further comprising:

extracting inphase and quadrature components of said wireless signal; and

digitizing the inphase and quadrature components for subsequent processing.

16. A system for monitoring the location of objects, comprising:

at least one cell controller unit connected to at least one transmission antenna for transmitting a cell controller signal modulated onto a carrier signal at a first frequency and at a selected transmission time, and connected to at least one reception antenna for receiving a responding tag signal containing a tag datagram at a second frequency and at a reception time;

at least one tag unit having a translation circuitry for translating each received cell controller signal into the tag signal, said at least one tag unit being a passive tag unit having no active internal power source for signal transmission;

at least one external power source that provides a wireless power source to the at least one tag unit, at least one external power source being physically separated from at least one reception antenna so that a tag unit that is powered by the external power source would not be so powered by the external power source if the external power source was located at the reception antenna that receives a responding tag signal from the tag unit; and

at least one calculation unit connected to each cell controller for calculating the location of each tag unit based on the reception time at least one reception antenna.

17. The system of claim 16, further comprising:

at least one active tag unit having an internal power source that is a low power battery, said at least one active tag unit being in a low power state between consecutive transmissions of a received cell controller signal.

18. The system of claim 16, wherein said external power source is a wireless power source that includes one or more capacitors and one or more inductors.

19. The system of claim 16, wherein said tag datagram includes error correction bits.

20. The system of claim 16, wherein said tag datagram includes a validity check.

21. The system of claim 16, wherein said tag datagram includes data derived from an object associated with said at least one tag unit.

22. A system for locating an object, comprising:

a first tag, to be associated with said object, that transmits a first signal at a first frequency, said first tag being adapted to operate as both a passive tag or an active tag, said first tag operating as a passive tag when receiving power from an external power source to transmit said first signal, and said first tag operating as an active tag when using power from an internal power source to transmit said first signal.

23. The system of claim 22, wherein the first tag operates as a passive tag when the internal power source is depleted.

24. The system of claim 22, further comprising a cell controller that transmits an interrogation signal at an input frequency, and said tag responds to said interrogation signal by transmitting said first signal.

25. The system of claim 22, wherein said first tag is a radio frequency identification tag.

26. The system of claim 22, wherein the first tag operates as a passive tag when in sufficient proximity to an external source of wireless power regardless of a depletion state of the internal power source.

27. The system of claim 22, further comprising:

a cell controller that transmits an interrogation signal and includes a receiver for receiving the first signal, the receiver having a receiving portion that receives the first signal in a wireless form; and

an external power source that provides a wireless power source to the first tag, the external power source being physically separated from the receiving portion of the receiver so that the first tag would not be powered by the external power source if the external power source was located at the receiving portion.