Low cost DTOA location processing system based on multiple readers-to-single processor architecture

• US 6,593,885 B2
• Filed: 04/20/2001
• Issued: 07/15/2003
• Est. Priority Date: 04/27/2000
• Status: Expired due to Term

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation (Zebra Technologies Corporation)
• Inventors: Wisherd, David S., Belcher, Donald K.
• Primary Examiner(s): Hellner, Mark
• Application Number:
  US09/839,573
• Publication Number:
  US 20020039080A1
• Time in Patent Office: 816 Days
• Field of Search: 342/450, 342/465, 342/463
• US Class Current: 342/463
• CPC Class Codes: G01S 13/767 Responders; Transponders teaching or practice apparatus for gun-aiming or gun-laying using reflecting targets or active targets F41G3/26
• 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 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0295 Proximity-based methods, e.g. position inferred from reception of particular signals
• CPC Class Codes: G01S 7/003 Transmission of data between radar, sonar or lidar systems and remote stations
• 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
• 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 time division multiplexed reader to shared RF channel processor signal transport network for a geolocation system in which the number of readers is relatively small, allowing the use of only a single shared RF channel processor. The differential signal transport delays among respective segments of the network creates an inherent set of time division multiplexed time slots for the various readers, that allows the shared RF channel processor to receive and process the output of each reader in a known, independent time frame.

Claims

1. For use with a system for locating objects within a monitored environment, wherein wireless transmissions from tags associated with objects are detected at a plurality of spaced apart tag transmission readers, and outputs of said tag transmission readers are processed to locate said tags and thereby their associated objects within a monitored environment, a method comprising the steps of:

(a) time-division-multiplexing said outputs of said tag transmission readers to a shared processor which is operative to process outputs of and identify first-to-arrive tag transmissions at said tag transmission readers; and

(b) processing signals representative of said first-to-arrive tag transmissions as identified by said shared processor so as to geolocate said tags and thereby their associated objects within said monitored environment.

2. The method according to claim 1, wherein step (a) comprises time-division-multiplexing outputs of said tag transmission readers to said shared processor by way of signal transport paths that impart delays providing isolation with respect to delayed multi-path signals within a tag transmission detection interval.

3. The method according to claim 1, wherein said tag transmission readers are daisy chain-coupled to said shared processor.

4. The method according to claim 1, wherein said tag transmission readers are star-coupled to said shared processor.

5. The method according to claim 1, wherein a selected tag transmission reader is located at a spatial location that will ensure first detection thereby of a tag transmission from any of said tags.

6. The method according to claim 1, wherein that tag transmission reader having a first time slot within a sequence of time-division-multiplexed outputs of said tag transmission readers to said shared processor is located at a spatial location that will ensure first detection thereby of a tag transmission from any of said tags.

7. The method according to claim 1, wherein step (a) includes incorporating information representative of the identification of a respective reader as part the output thereof that is time-division-multiplexed to said shared processor.

8. The method according to claim 7, wherein step (a) includes modulating the output of a respective reader with information representative of the identification of said respective reader.

9. The method according to claim 8, wherein step (a) includes amplitude modulating the output of a respective reader with information representative of the identification of said respective reader.

10. The method according to claim 8, wherein step (a) includes phase modulating the output of a respective reader with information representative of the identification of said respective reader.

11. For use with a system for locating objects, wherein wireless transmissions from tags associated with objects are detected at a plurality of spaced apart tag transmission readers, a subsystem for processing outputs of said tag transmission readers to locate said tags and thereby their associated objects within a monitored environment, said system comprising:

a shared reader processor that is operative to process outputs of and identify first-to-arrive tag transmissions at said tag transmission readers; and

a transport path arrangement coupled between said tag transmission readers and said shared reader processor that is adapted to time-division-multiplex outputs of said tag transmission readers to said shared processor, and wherein signals representative of first-to-arrive tag transmissions identified by said shared reader processor are processed to geolocate said tags and thereby their associated objects within said monitored environment.

12. The subsystem according to claim 11, wherein said transport path arrangement includes signal transport paths that impart delays providing isolation with respect to delayed multi-path signals within a tag transmission detection interval.

13. The subsystem according to claim 11, wherein said transport path arrangement has a daisy-chain configuration.

14. The subsystem according to claim 11, wherein said transport path arrangement has a star configuration.

15. The subsystem according to claim 11, wherein a selected tag transmission reader is located at a spatial location that will ensure first detection thereby of a tag transmission from any of said tags.

16. The subsystem according to claim 11, wherein that tag transmission reader having a first time slot within a sequence of time-division-multiplexed outputs of said tag transmission readers to said shared processor is located at a spatial location that will ensure first detection thereby of a tag transmission from any of said tags.

17. The subsystem according to claim 11, wherein a respective reader output incorporates information representative of the identification of said respective reader that is time-division-multiplexed by said transport path arrangement to said shared processor.

18. The subsystem according to claim 17, wherein a respective reader is coupled to a modulator which is adapted to modulate the output of said respective reader with information representative of the identification thereof, and wherein said transport path arrangement is operative to transmit said information to said shared processor.

19. The subsystem according to claim 18, wherein said modulator comprises one of an amplitude modulator, and a phase modulator.

20. A communication subsystem for use with a system for locating objects, wherein wireless transmissions from tags associated with objects are detected at a plurality of spaced apart tag transmission readers, comprising:

a shared reader processor that is operative to process outputs of and identify first-to-arrive tag transmissions at said tag transmission readers supplied thereto;

a transport path arrangement coupled between said tag transmission readers and said shared reader processor and being operative to time-division-multiplex outputs of said tag transmission readers to said shared processor; and

a location processor which is operative to process signals representative of said first-to-arrive tag transmissions identified by said shared reader processor to geolocate said tags and thereby their associated objects within said monitored environment.