Geolocation system with controllable tags enabled by wireless communications to the tags

• US 20020094012A1
• Filed: 03/02/2001
• Published: 07/18/2002
• Est. Priority Date: 03/07/2000
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation (Zebra Technologies Corporation)
• Inventors: Belcher, Donald K.
• Granted Patent: US 6,859,485 B2
• Time in Patent Office: Days
• US Class Current: 375/130
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted
• 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 5/02 using radio waves using satellite radio beacon systems for determining position G01S19/00
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 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: H04B 1/69 Spread spectrum techniques

Abstract

An auxiliary wireless communication mechanism is incorporated into a system that geolocates tagged objects within a monitored environment, using random, repetitive spread spectrum emissions from the tags. The emissions are detected at tag emission readers, and processed by an object location processor to geolocate the tagged objects. The auxiliary wireless communication mechanism transmits a return spread spectrum signal containing information intended for a tag immediately in response to the object location processor geolocating the tag. This immediately returned spread spectrum transmission allows a reduced complexity spread spectrum receiver within the tag to despread the return signal without having to determine the timing of the clock signal used to produce it.

Claims

1. A method of operating a system for geolocating objects within a monitored environment, in which emissions from tags associated with said objects are detected at a plurality of spaced apart tag emission readers, and outputs of said tag emission readers are processed by an object location processor to geolocate said tags and thereby their associated objects within said monitored environment, said method comprising the steps of:

(a) in response to said object location processor geolocating a tag, transmitting, from a location spaced apart from said tag, a spread spectrum signal containing information intended for said tag; and

(b) at said geolocated tag, receiving said spread spectrum signal transmitted in step (a) and recovering said information.

2. The method according to claim 1, wherein step (b) comprises despreading the received spread spectrum signal, without determining information representative of a clock signal used to produce said spread spectrum signal transmitted in step (a).

3. The method according to claim 1, wherein step (b) comprises despreading the received spread spectrum signal using a tag-resident clock generated independent of a clock signal used to produce said spread spectrum signal transmitted in step (a).

4. The method according to claim 1, wherein step (a) comprises initiating transmission of said spread spectrum signal relative to a prescribed attribute of an emission from said tag as received by said tag emission readers.

5. The method according to claim 4, wherein step (a) comprises initiating transmission of said spread spectrum signal relative to the time of termination of said emission from said tag as received by said tag emission readers.

6. The method according to claim 4, wherein step (b) comprises enabling a despreading mechanism within said tag for a prescribed period of time following termination of said emission from said tag, and causing the enabled despreading mechanism to despread the received spread spectrum signal using a tag-resident clock generated independent of a clock signal used to produce said spread spectrum signal transmitted in step (a).

7. The method according to claim 1, wherein step (a) comprises transmitting said spread spectrum signal containing information intended for said tag from a location proximate to a tag emission reader.

8. A transceiver for a wireless communication tag adapted for use with an object in an environment that is monitored by a system for geolocating objects therein, said transceiver comprising:

a spread spectrum generator containing a spreading mechanism that is adapted to generate a spread spectrum signal in accordance with a tag-resident clock;

a tag transmitter which is adapted to emit said spread spectrum signal generated by said spread spectrum generator, so that said spread spectrum signal emitted by said tag transmitter may be detected by a plurality of spaced apart tag emission readers, outputs of which are processed by an object location processor to geolocate said wireless communication tag and thereby said object within said monitored environment;

a spread spectrum receiver adapted to receive a spread spectrum signal transmitted from a remote transmitter; and

a despreader, which is adapted to despread the spread spectrum signal received from said remote transmitter, using said spreading mechanism and said tag-resident clock.

9. The transceiver according to claim 8, wherein said despreader is operative to despread the spread spectrum signal received from said remote transmitter, without determining information representative of a clock signal used to produce the spread spectrum signal transmitted by said remote transmitter.

10. The transceiver according to claim 8, wherein said remote transmitter is operative to initiate transmission of said spread spectrum signal relative to a prescribed attribute of an emission from said tag as received by said tag emission readers.

11. The transceiver according to claim 10, wherein said remote transmitter is operative to initiate transmission of said spread spectrum signal relative to the time of termination of said emission from said tag as received by said tag emission readers.

12. The transceiver according to claim 10, wherein said despreader is enabled for a prescribed period of time following termination of said emission by said tag transmitter, and is operative to despread a spread spectrum signal received from said remote transmitter during said prescribed period of time using said tag-resident clock.

14. The method according to claim 13, wherein step (c) comprises despreading the return spread spectrum signal received from said remote transmitter, without determining information representative of a clock signal used to produce the return spread spectrum signal transmitted by said remote transmitter in step (b).

15. The method according to claim 13, wherein step (b) comprises initiating transmission of said return spread spectrum signal relative to a prescribed attribute of an emission from said tag as received by said tag emission readers.

16. The method according to claim 15, wherein step (b) comprises initiating transmission of said return spread spectrum signal relative to the termination of an emission from said tag as received by said tag emission readers.

17. The method according to claim 15, wherein step (c) comprises enabling a despreader that is operative to despread said return spread spectrum signal received from said remote transmitter for a prescribed period of time following termination of emission of said spread spectrum signal in step (a) sing said tag-resident clock.

18. The method according to claim 13, wherein step (b) comprises transmitting said return spread spectrum signal from a location proximate to a tag emission reader.

20. The wireless communication subsystem according to claim 19, wherein said spread spectrum receiver is adapted to despread said return spread spectrum signal transmitted from said spread spectrum transmitter, without determining information representative of a clock signal used to produce said return spread spectrum signal transmitted by spread spectrum transmitter.

21. The wireless communication subsystem according to claim 19, wherein spread spectrum receiver is operative to despread said return spread spectrum signal using a tag-resident clock generated independent of a clock signal used to produce said return spread spectrum signal transmitted by said spread spectrum transmitter.

22. The wireless communication subsystem according to claim 19, wherein said spread spectrum transmitter is operative to initiate transmission of said return spread spectrum signal relative to a prescribed timing attribute of an emission from said tag as received by said tag emission readers.

23. The wireless communication subsystem according to claim 19, wherein said spread spectrum receiver contains a despreading mechanism that is enabled for a prescribed period of time following termination of said emission from said tag, and is operative to despread said return spread spectrum signal using a tag-resident clock generated independent of a clock signal used to produce said return spread spectrum signal transmitted by said spread spectrum transmitter.

24. The wireless communication subsystem according to claim 19, wherein said spread spectrum transmitter is located proximate to a tag emission reader.

13. A method for conducting wireless communications between a wireless communication tag, adapted for use with an object in an environment that is monitored by a system for geolocating objects therein, and a transmitter of said system, said method comprising the steps of:

(a) in said wireless communication tag, generating a spread spectrum signal in accordance with a tag-resident clock, and emitting said spread spectrum signal, so that said spread spectrum signal may be detected by a plurality of spaced apart tag emission readers, outputs of which are processed by an object location processor to geolocate said wireless communication tag and thereby said object within said monitored environment;

(b) in response to said object location processor geolocating said tag, transmitting, from a location spaced apart from said tag, a return spread spectrum signal containing information intended for said tag; and

(c) in said wireless communication tag, receiving said return spread spectrum signal transmitted from said remote transmitter in step (b), and despreading the return spread spectrum signal received from said remote transmitter, using said spreading mechanism and said tag-resident clock employed in step (a).

19. A wireless communication subsystem adapted for use with a system for geolocating objects within a monitored environment, in which emissions from tags associated with said objects are detected at a plurality of spaced apart tag emission readers, and outputs of said tag emission readers are processed by an object location processor to geolocate said tags and thereby their associated objects within said monitored environment, said wireless communication subsystem comprising:

a spread spectrum transmitter associated with said object geolocation system and being adapted to transmit a return spread spectrum signal containing information intended for a tag in response to said object location processor geolocating said tag; and

a spread spectrum receiver within said geolocated tag that is adapted to receive said return spread spectrum signal transmitted by said transmitter and to recover said information.