Method and apparatus for reducing the time required to acquire a GPS signal

• US 9,252,826 B2
• Filed: 09/19/2013
• Issued: 02/02/2016
• Est. Priority Date: 05/19/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Van Diggelen, Frank, Abraham, Charles
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US14/031,927
• Publication Number:
  US 20140098910A1
• Time in Patent Office: 866 Days
• Field of Search: 375/139, 375/140, 375/142, 375/145, 375/147, 375/149, 375/150, 375/316, 375/343, 375/354, 375/355, 342/352, 342/357.22, 342/357.23, 342/357.24, 342/357.34, 342/357.42, 342/357.43, 342/357.44
• US Class Current: 1/1
• CPC Class Codes: G01S 19/05 providing aiding data
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/26 involving a sensor measurement for aiding acquisition or tracking
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/16 Circuits
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence

Abstract

A method of correlating a digital communications signal is described. In an example, a window is defined equal to a portion of an epoch of the digital communication signal. The digital communication signal is then correlated across the window. A determination is made as to whether a correlation peak results from the correlating. Timing parameters are then established for receiving additional digital communication signals in response to presence of the correlation peak.

Claims

1. An apparatus for correlating a communication signal received from a first satellite, comprising:

a microcontroller configured to select a window equal to a portion of an epoch of the communication signal; and

a processing channel comprising a plurality of correlators each configured to correlate the communication signal with a reference code shifted relative to the communication signal by a different amount of time within the selected window to identify a correlation peak,

wherein the microcontroller is further configured to establish a timing parameter, based on a location of the selected window within the epoch, for reducing a search range for an additional communication signal from a second satellite.

2. The apparatus of claim 1, wherein the communication signal is a Global Positioning System (GPS) signal.

3. The apparatus of claim 1, wherein the communication signal includes an in-phase component and a quadrature component.

4. The apparatus of claim 1, further comprising a tuner configured to remove a Doppler frequency shift from the communication signal.

5. The apparatus of claim 1, wherein the microcontroller is further configured to divide the epoch of the communication signal into equal portions and to select one of the equal portions as the window.

6. The apparatus of claim 1, wherein the portion of the epoch corresponds to the epoch divided by an integer number.

7. The apparatus of claim 1, wherein the reference code includes 1023 chips.

8. The apparatus of claim 1, wherein a first correlator of the plurality of correlators is configured to correlate the communication signal with a first time shifted version of the reference code, wherein a second correlator of the plurality of correlators is configured to correlate the communication signal with a second time shifted version of the reference code, and wherein the second time shifted version of the reference code corresponds to the first time shifted version of the reference code time shifted by a half of a chip of the reference code.

9. The apparatus of claim 1, wherein the timing parameter includes a clock bias.

10. A method for correlating a communication signal received from a first satellite, comprising:

selecting a window equal to a portion of an epoch of the communication signal;

performing, in parallel, a plurality of correlations of the communication signal with reference code shifted relative to the communication signal by different amounts of time within the selected window to identify a correlation peak; and

establishing a timing parameter, based on a location of the selected window within the epoch, for reducing a search range for an additional communication signal from a second satellite.

11. The method of claim 10, wherein selecting the window comprises dividing the epoch into equal portions and selecting one of the equal portions as the window.

12. The method of claim 10, wherein the reference code includes 1023 chips.

13. The method of claim 10, wherein the portion of the epoch corresponds to the epoch divided by an integer number.

14. The method of claim 13, wherein the timing parameter includes a clock bias.

15. An apparatus for correlating a communication signal received from a first satellite, comprising:

a microcontroller configured to select a window equal to a portion of an epoch of the communication signal; and

a processing channel configured to correlate the communication signal with a reference code within the selected window to identify a correlation peak,

wherein the microcontroller is further configured to establish a timing parameter, based on a location of the selected window within the epoch, for reducing a search range for an additional communication signal from a second satellite.

16. The apparatus of claim 15, wherein the communication signal includes a Global Positioning System (GPS) signal.

17. The apparatus of claim 15, wherein the microcontroller is further configured to divide the epoch of the communication signal into equal portions and to select one of the equal portions as the window.

18. The apparatus of claim 15, wherein the processing channel comprises a plurality of correlators, wherein a first correlator of the plurality of correlators is configured to correlate the communication signal with a first time shifted version of the reference code, wherein a second correlator of the plurality of correlators is configured to correlate the communication signal with a second time shifted version of the reference code, and wherein the second time shifted version of the reference code corresponds to the first time shifted version of the reference code time shifted by a half of a chip of the reference code.

19. The apparatus of claim 15, wherein the timing parameter includes a clock bias.