Time transfer utilizing ultra wideband signals

• US 20060291537A1
• Filed: 05/28/2005
• Published: 12/28/2006
• Est. Priority Date: 06/14/1999
• Status: Active Grant

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Richards, James L., Fullerton, Larry W., Roberts, Mark D.
• Granted Patent: US 7,649,925 B2
• Time in Patent Office: Days
• US Class Current: 375/145
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 7/4052 by simulation of echoes
• CPC Class Codes: G01S 7/4065 involving a delay line
• CPC Class Codes: G01S 7/4069 involving a RF signal injection
• CPC Class Codes: G01S 7/4082 using externally generated reference signals, e.g. via remote reflector or transponder
• CPC Class Codes: G06K 7/10306 ultra wide band
• CPC Class Codes: H04B 1/7183 Synchronisation

Abstract

Time is transferred from an ultra wideband (UWB) transmitter to UWB receiver by transmitting a signal structure having an associated timing reference point together with a time value for the timing reference point. The UWB receiver receives the timing signal structure by synchronizing a receiver time base to the signal structure, demodulating the time value information, and using the demodulated time value information to set a receiver clock value. Propagation delay information is used to adjust the receiver clock value by advancing the receiver clock value to account for the propagation delay. In one embodiment, propagation delay is determined from a known distance between the transmitter and receiver. In another embodiment, the transmitter and receiver are part of a two-way link wherein propagation delay is measured by round trip timing measurements.

Claims

1. A method for transferring timing between a transmitter and a receiver comprising:

transmitting an ultra wideband signal having a structure corresponding to a source time clock;

receiving the ultra wideband signal;

synchronizing a receiver time base with the received ultra wideband signal;

determining the signal structure; and

setting a receiver clock in accordance with the receiver time base and the signal structure.

2. The method of claim 1 wherein the signal structure includes a time reference point and includes a time value related to the time of the time reference point.

3. The method of claim 1 further including the step of determining propagation delay and adjusting the receiver clock in accordance with propagation delay.

4. The method of claim 3 wherein the step of determining propagation delay comprises a leading edge algorithm.

5. The method of claim 3, wherein the step of determining propagation delay comprises a pattern matching algorithm.

6. The method of claim 1 wherein the signal structure includes a code and the synchronizing step uses the code to synchronize the time base with the signal structure.

7. The method of claim 6 wherein the code is periodically changed to effectively extend the code repeat length.

8. The method of claim 6 wherein the code is applied to groups of pulses and the spacing between groups of pulses is changed to effectively extend the code repeat length.

9. A method for transferring a time reference, comprising:

transmitting from a first UWB radio a UWB signal having a structure corresponding to said time reference;

receiving at a second UWB radio said UWB signal; and

setting a second time reference at said second UWB radio in accordance with said structure.

10. The method as in claim 9, wherein said second time reference is set based upon a propagation delay corresponding to said received UWB signal.

11. A method for transferring a time reference, comprising:

determining a propagation delay of a received UWB signal having a structure corresponding to said time reference; and

setting a second time reference based upon said determination of said propagation delay and said structure.

12. The method as in claim 11, wherein said received UWB signal results from a direct path between a transmitting UWB radio and a receiving UWB radio.

13. The method as in claim 11, wherein said received UWB signal results from an indirect path between a transmitting UWB radio and a receiving UWB radio.

14. The method as in claim 11, wherein said determination of said propagation delay corresponds to a distance determined using UWB distance determination techniques.

15. The method as in claim 11, wherein said determination of said propagation delay corresponds to the delay for a known distance.

16. The method of claim 11 wherein the signal structure includes a time reference point and a time value related to the time of the time reference point.

17. A method for transferring timing between a first transceiver and a second transceiver comprising:

transmitting an ultra wideband signal from said first transceiver, said signal having a first signal structure corresponding to a source time clock;

receiving the ultra wideband signal at the second transceiver;

synchronizing a second transceiver receiver time base with the received ultra wideband signal;

transmitting a return signal from said second transceiver, said return signal having a known timing relationship to said second transceiver receiver time base;

receiving said return signal at said first transceiver;

determining propagation delay between said first transceiver and said second transceiver; and

setting a second transceiver clock in accordance with the second transceiver receiver time base and the first signal structure and propagation delay.

18. The method of claim 17, further including setting the timing of the return signal based on propagation delay.

19. The method of claim 17, wherein the step of determining propagation delay includes the steps of:

generating a first multipath pattern resulting from transmission from the first transceiver to the second transceiver;

generating a second multipath pattern resulting from transmission from the second transceiver to the first transceiver; and

comparing the first multipath pattern with the second multipath pattern.

20. The method of claim 19 wherein the comparing step includes correlation matching the first multipath pattern with the second multipath pattern.

21. The method of claim 17 wherein the calculation of propagation delay includes a process for correcting internal errors, said process comprising the steps of:

transmitting a signal from said second transceiver;

receiving a portion said transmitted signal, said portion having a known time difference relationship to said second transceiver receiver timing;

using the timing of said return signal to adjust the second transceiver transmitter timing.

22. The method of claim 21 wherein the return signal comprises a reflection related to an antenna.

23. The method of claim 21 wherein the return signal comprises a portion of a transmitted signal delayed by a delay line.