Real-time locating system and method using timing signal

• US 20020181565A1
• Filed: 05/03/2002
• Published: 12/05/2002
• Est. Priority Date: 05/04/2001
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Wherenet Corporation (Zebra Technologies Corporation)
• Inventors: Belcher, Donald K., Boyd, Robert W., Wohl, Michael A., Wisherd, David S.
• Granted Patent: US 7,212,563 B2
• Time in Patent Office: Days
• US Class Current: 375/152
• CPC Class Codes: G01S 5/02216 Timing or synchronisation of the receivers
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A location system includes a plurality of signal readers for receiving signals from a wireless transmitter to be located. The signals include a wideband, spread spectrum signal and a timing marker appended a predetermined time in front of the wideband, spread spectrum signal for indicating the presence of the wideband, spread spectrum signal. A location processor is operatively coupled to the signal readers for detecting the timing markers of signals and responsive to a detection of a timing marker, correlating a signal as a first-to-arrive signal and conducting differentiation of first-to-arrive signals to locate a wireless transmitter.

Claims

1. A location system comprising:

a plurality of signal readers for receiving signals from a wireless transmitter to be located, said signals comprising a wideband, spread spectrum signal and a timing marker appended a predetermined time in front of the wideband, spread spectrum signal for indicating the presence of the wideband, spread spectrum signal; and

a location processor operatively coupled to said signal readers for detecting the timing markers of signals and responsive to a detection of a timing marker, correlating a signal as a first-to-arrive signal and conducting differentiation of first-to-arrive signals to locate a wireless transmitter.

2. A location system according to claim 1, wherein said timing marker is timed about 80 to about 120 nanoseconds in front of the wideband, spread spectrum signal.

3. A location system according to claim 1, wherein said timing marker comprises a wireless local area network transmission.

4. A location system according to claim 3, and further comprising an access point base station operative with a location processor and at least one signal reader.

5. A location system according to claim 1, wherein said location processor comprises a matched filter correlator.

6. A location system according to claim 5, wherein said matched filter correlator further comprises matched filter banks having parallel correlators that correlate a received communications signal with time offset versions of a reference spreading code.

7. A location system according to claim 1, wherein said location processor further comprises a plurality of processors for distributing processing capability.

8. A location system according to claim 1, wherein three signal readers are used for determining the location of a wireless transmitter.

9. A location system according to claim 1, wherein each signal reader comprises a plurality of mutually diverse antennas for detecting signals at each signal reader.

10. A location system according to claim 1, wherein each wireless transmitter comprises a tag transmitter that is coupled with an object to be located.

11. A location system according to claim 10, wherein said wideband, spread spectrum signal includes identification data regarding the object to which the tag transmitter is coupled.