Locating system and method employing radio frequency tags

• US 6,040,774 A
• Filed: 05/27/1998
• Issued: 03/21/2000
• Est. Priority Date: 05/27/1998
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: Sarnoff Corporation (SRI International, Inc.)
• Inventors: Schepps, Jonathan Lloyd
• Primary Examiner(s): TONG, NINA C
• Application Number:
  US09/085,410
• Time in Patent Office: 664 Days
• Field of Search: 340/572.1, 340/568.1, 340/571, 340/904, 340/825.54, 340/825.08, 340/825.06, 340/825.36, 340/825.49, 340/825.69, 342/463, 342/465, 342/457, 342/387, 342/450
• US Class Current: 340/572.1
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• 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 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas

Abstract

A locating system and method employs a plurality of radio frequency readers arrayed with respect to a region having a plurality of zones within which a plurality of radio frequency tags are to be located. Each reader identifies those tags present within its coverage area. The coverage areas of all the readers taken together substantially cover the region and at least part of the coverage area of each reader overlaps at least part of the coverage area of at least one other reader. A data processor receives the identification of the tags within the coverage area of each reader and applies a set of locating rules to determine therefrom in which zone within the region each identified tag is located.

Claims

1. Apparatus for locating a tag comprising:

at least first and second readers each having a respective coverage area in which a tag can be identified, wherein at least a part of the coverage area of said first reader overlaps at least a part of the coverage area of said second reader; and

a processor responsive to said first and second readers to identify a tag located in one of (a) the overlap of the coverage areas of said first and second readers and (b) in the coverage area of said first reader but not in the coverage area of said second reader.

2. The apparatus of claim 1 wherein said processor includes a set of locating rules defining locations within a region in terms of presence and absence of identification of a tag within the coverage areas of said first and second readers and the overlap of said coverage areas.

3. The apparatus of claim 2 wherein said set of locating rules defines locations within a region in terms of a time of the presence or absence of identification of a tag within the coverage areas of said first and second readers and the overlap of said coverage areas.

4. The apparatus of claim 1 wherein said first and second readers receive an identification data signal from each tag that is within its respective coverage area.

5. The apparatus of claim 4 wherein each of said first and second readers includes a respective antenna having a beam pattern defining its respective coverage area, and said identification data signal is a radio frequency signal received by said antenna.

6. The apparatus of claim 4 wherein said first and second readers transmit an interrogation signal for initiating said identification data signal.

7. The apparatus of claim 1 in combination with a plurality of tags each communicating an identification signal adapted to be received by said first and second readers.

8. Apparatus for locating coded articles within a predetermined region comprising:

a number N of reader units each for identifying coded articles present within its respective coverage pattern, wherein said N reader units are arranged to have overlapping coverage patterns defining with said coverage patterns at least 2N-1 coverage zones within said predetermined region, wherein at least one of said 2N-1 coverage zones is within the coverage pattern of only one of said N reader units; and

a processor including a set of locating rules and coupled to said N reader units for receiving indications of coded articles identified by each said reader unit, said processor locating the identified coded articles to ones of said 2N-1 coverage zones in accordance with said set of locating rules.

9. The apparatus of claim 8 further including a data bus for coupling said indications of coded articles identified by each of said N reader units to said processor.

10. The apparatus of claim 8 wherein each of said N reader units generates said indications of coded articles in response to receiving identification signals transmitted by said coded articles.

11. The apparatus of claim 8 wherein said coverage zones comprise areas of overlapping coverage patterns of said N reader units and areas of said coverage patterns not overlapping another coverage pattern.

12. The apparatus of claim 8 in combination with a plurality of coded articles each transmitting identification signals adapted to be identified by said N reader units.

13. Apparatus for locating coded articles within a predetermined region comprising:

an array of reader units each having a respective coverage area in which a coded article is identified if present, said reader units being arrayed so that their coverage areas taken together substantially cover said predetermined region and so that at least a part of the respective coverage area of each said reader unit is also covered by the respective coverage area of at least one other reader unit, thereby to define a plurality of zones comprising said predetermined region;

a data processor having a memory for storing coded article identification data therein and having a set of locating rules stored therein; and

a data communicator coupled between each of said reader units and said data processor for storing in said memory of said data processor coded article identification data produced by said array of reader units in response to each identified coded article present in the respective coverage area of each reader unit, whereby an indicia of the presence and identity of each coded article present is stored in the memory of said data processor;

wherein said data processor processes said coded article identification data in accordance with said set of locating rules to locate each coded article present in said predetermined region within one of said plurality of zones.

14. The apparatus of claim 13 wherein each said reader unit receives an identification data signal from each tag that is present within its respective coverage area.

15. The apparatus of claim 13 wherein each of said reader units includes a respective antenna having a beam pattern defining its respective coverage area.

16. The apparatus of claim 13 wherein said set of locating rules defines said zones in terms of presence and absence of identification of tags within the respective coverage areas of each of said reader units and within areas covered by the respective coverage areas of more than one of said reader units.

17. The apparatus of claim 13 wherein said array of reader units is a linear array.

18. The apparatus of claim 13 wherein said array of reader units is an array about a periphery of said predetermined region.

19. The apparatus of claim 13 wherein said array of reader units includes a plurality of reader units substantially centrally located within said predetermined region.

20. The apparatus of claim 13 in combination with a plurality of coded articles each transmitting an identification signal to ones of said array of reader units.

21. The apparatus of claim 20 wherein said predetermined region includes a facility for vehicles and wherein said coded articles are associated with vehicles.

22. The apparatus of claim 20 wherein said predetermined region includes an entertainment facility and wherein said coded articles are associated with moveable entertainment exhibits.

23. The apparatus of claim 22 wherein said moveable entertainment exhibits include animals.

24. A method of locating coded articles within a predetermined region including respective overlapping coverage areas of ones of a plurality of readers, comprising:

identifying the coded articles present within the respective coverage area of each one of said plurality of readers;

combining the coded article identifications from each one of said plurality of readers;

applying a set of locating rules to the combined coded article identifications; and

identifying each of the coded articles to a location within said predetermined region in accordance with said set of locating rules.

25. The method of claim 24 wherein applying a set of locating rules includes:

determining the combination of respective coverage areas in which each coded article is located; and

comparing the determined combinations of respective coverage areas to a predetermined correspondence of combinations of coverage areas to locations.

26. The method of claim 24 wherein identifying the coded articles present includes:

transmitting from said coded articles an identification signal; and

receiving said identification signal at ones of said plurality of readers.

27. The method of claim 24 wherein combining the coded article identifications includes polling each one of said plurality of readers to obtain indicia of identified coded articles therefrom.

28. A system for locating rental vehicles within zones in a rental vehicle facility comprising:

a plurality of coded tags, each tag being affixed to a rental vehicle;

an array of reader units arrayed about said rental vehicle facility for identifying coded tags within respective coverage areas of ones of said reader units; and

a data processor coupled to said reader units for receiving indicia of the coded tags identified by said reader units and for applying a set of locating rules to locate said rental vehicles within a number of zones in said rental vehicle facility, wherein the number of said zones exceeds the number of said reader units.

29. A system for locating moveable objects within zones in an entertainment facility comprising:

a plurality of coded tags, each tag being affixed to a moveable object;

an array of reader units arrayed about said entertainment facility for identifying coded tags within respective coverage areas of ones of said reader units; and

a data processor coupled to said reader units for receiving indicia of the coded tags identified by said reader units and for applying a set of locating rules to locate said moveable objects within a number of zones in said entertainment facility, wherein the number of said zones exceeds the number of said reader units.