High sensitivity GPS-assisted time source

• US 8,184,505 B1
• Filed: 03/23/2011
• Issued: 05/22/2012
• Est. Priority Date: 01/02/2008
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm Atheros Incorporated (Qualcomm, Inc.)
• Inventors: Wang, Yi-Hsiu, Hilgenberg, Dennis
• Primary Examiner(s): MISKA, VIT W
• Application Number:
  US13/070,423
• Time in Patent Office: 426 Days
• Field of Search: 368/47, 342/357.01, 342/357.03, 342/357.06, 342/357.08, 342/357.12, 342/357.62, 342/357.63, 342/357.69, 375/142, 375/145, 375/150, 375/343, 375/368
• US Class Current: 368/47
• CPC Class Codes: G01S 19/243 Demodulation of navigation message
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition
• CPC Class Codes: G01S 19/39 the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
• CPC Class Codes: G04R 20/04 Tuning or receiving; Circuits therefor

Abstract

A method for determining portions of a GPS satellite signal may use non-coherent integration to determine a repeated pattern such as a preamble. Once the repeated pattern is determined, portions of the GPS satellite signal that may be determined with partial correlation sums. Sensitivity to satellite signals may be increased by computing more partial correlation sums on portions of the GPS satellite signal. In one embodiment, time of day information may be determined from the GPS satellite signal with partial correlation sums.

Claims

1. A method for determining time of day, the method comprising:

receiving a signal from at least one of a plurality of satellites;

determining a CA code, code phase and Doppler frequency associated with the signal; and

determining the time of day from the signal by calculating at least one partial correlation sum without the necessity of generating a fix.

2. The method of claim 1, wherein the satellites are selected from at least one of the group of Navstar, GLONASS and Galileo.

3. The method of claim 1, further comprising:

synchronizing a clock to the determined time of day.

4. The method of claim 1, wherein calculating at least one partial correlation sum includes:

determining a position of a preamble in the signal; and

determining a subset of a hand-over-word based on the position of the preamble and hypothetical sequences of the subset.

5. The method of claim 4, further comprising performing non-coherent integration on the signal to determine the position of the preamble.

6. The method of claim 4, further comprising determining a first partial correlation sum using a first portion of the signal to determine a first subset of the hand-over-word.

7. The method of claim 6, further comprising determining a second partial correlation sum using the first portion of the signal to determine the first subset of the hand-over-word.

8. The method of claim 7, wherein the first and the second partial correlation sums are determined in parallel.

9. The method of claim 7, wherein the first and the second partial correlation sums are determined in serial.

10. The method of claim 6, wherein the first partial correlation sum is determined with a first hypothetical sequence.

11. The method of claim 7, wherein the second partial correlation sum is determined with a second hypothetical sequence.

12. The method of claim 7, further comprising determining a third partial correlation sum using the first portion of the signal, a second portion of the signal, and a third hypothetical sequence to determine a second subset of the hand-over-word.

13. An apparatus for determining time of day, the apparatus comprising:

an antenna configured to receive a signal from at least one of a plurality of satellites;

an RF section coupled to the antenna and configured to provide a IF signal from the received signal; and

an acquisition channel for determining a CA code, a code phase, and a Doppler frequency from the IF signal,

the acquisition channel including a non-coherent correlator configured to calculate at least one partial correlation sum from a subset of a hand-over-word of the IF signal to determine the time of day.

14. The apparatus of claim 13, wherein the non-coherent correlator is configured to perform non-coherent integration to determine a position of a preamble within the IF signal.

15. The apparatus of claim 13, wherein the non-coherent correlator is configured to determine a first partial correlation sum on a first portion of the IF signal to determine a first subset of the hand-over-word.

16. The apparatus of claim 15, wherein the first partial correlation sum is determined with a first hypothetical sequence.

17. The apparatus of claim 15, wherein the non-coherent correlator is configured to determine a second partial correlation sum on the first portion of the IF signal and a second portion of the IF signal to determine a second subset of the hand-over-word.

18. The apparatus of claim 17, wherein the second partial correlation sum is determined with a second hypothetical sequence.

19. The apparatus of claim 17, further including a controller for determining whether there are more bits within the subset of the hand-over-word to be determined.