METHOD AND APPARATUS FOR REDUCING THE TIME REQUIRED TO ACQUIRE A GPS SIGNAL

• US 20090304051A1
• Filed: 08/20/2009
• Published: 12/10/2009
• Est. Priority Date: 05/19/2003
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Charles Abraham, Frank Van Diggelen
• Inventors: Abraham, Charles, van Diggelen, Frank
• Granted Patent: US 8,571,147 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• 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. A method of correlating a digital communications signal, comprising:

(a) defining a window equal to a portion of an epoch of said digital communication signal;

(b) correlating said digital communication signal across said window;

(c) identifying whether a correlation peak results from said correlating; and

(d) establishing timing parameters for receiving additional digital communication signals in response to presence of said correlation peak.

2. The method of claim 1, further comprising:

(e) selecting another window within said epoch of said digital communication signal in response to absence of said correlation peak; and

(f) repeating steps (b), (c), (d), and (e) until said correlation peak is found.

3. The method of claim 1, wherein said window is half of said epoch.

4. The method of claim 1, wherein said window is a quarter of said epoch.

5. The method of claim 1, wherein said window is a third of said epoch.

6. The method of claim 1, wherein the digital communication signal is a GPS satellite signal.

7. The method of claim 1, wherein the digital communication signal is a GPS satellite signal transmitted from a first satellite, and the timing parameters are set in a second receiver channel used to receive a GPS satellite signal from a second satellite.

8. The method of claim 1, wherein said portion is defined in said defining step by:

dividing said epoch into multiple portions; and

selecting said portion from said multiple portions.

9. A method of establishing timing synchronization in a GPS receiver, comprising:

(a) receiving a GPS signal from a first GPS satellite, where the GPS signal repeats over a predefined time period;

(b) defining a window equal to a portion of the predefined time period;

(c) correlating said GPS signal across said window;

(d) identifying whether a correlation peak results from said correlating; and

(e) establishing timing parameters for receiving additional GPS signals transmitted by other GPS satellites in response to presence of said correlation peak.

10. The method of claim 9, wherein said predefined time period is one epoch of the GPS signal.

11. The method of claim 9, further comprising:

(f) selecting another window within said predefined period of said GPS signal in response to absence of said correlation peak; and

(g) repeating steps (c), (d), (e), and (f) until said correlation peak is found.

12. The method of claim 9, wherein said window is half of the predefined time period.

13. The method of claim 9, wherein said window is a quarter of the predefined time period.

14. The method of claim 9 wherein said window is a third of the predefined time period.

15. A method of establishing timing synchronization in a multi-channel GPS receiver, comprising:

(a) receiving a GPS signal from a first GPS satellite using a first channel, where the GPS signal repeats over a predefined time period;

(b) defining a window equal to half of the predefined time period;

(c) correlating said GPS signal across said window;

(d) identifying whether a correlation peak results from said correlating; and

(e) establishing timing parameters in a second channel of the GPS receiver for receiving a second GPS signal transmitted by a second GPS satellite in response to presence of said correlation peak.

16. The method of claim 15, further comprising:

(f) selecting another window equal to a second half of the predefined period in response to absence of said correlation peak; and

(g) repeating steps (c), (d), (e), and (f) until said correlation peak is found.

17. An apparatus for correlating a digital communications signal, comprising:

a correlator for correlating said digital communication signal across a window equal to a portion of a predefined period of said digital communication signal;

a microcontroller for identifying whether a correlation peak results from said correlating and for establishing timing parameters for receiving additional digital communication signals in response to presence of said correlation peak.

18. The apparatus of claim 17, wherein said correlator correlates said digital communication signal across another window within said predefined period of said digital communication signal in response to absence of said correlation peak.

19. The apparatus of claim 17, wherein said digital communication signal is a GPS satellite signal transmitted from a first satellite, and said timing parameters are set in a second receiver channel used to receive a GPS satellite signal from a second satellite.