# US 8,571,147 B2 · Method and apparatus for reducing the time required to acquire a GPS signal

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- Number: US 8,571,147 B2
- Document ID: US8571147B2
- Status: Granted
- Kind: B2
- Application number: 12/544,600
- Filed: 2009-08-20
- Published: 2009-12-10
- Granted: 2013-10-29
- Earliest claimed: 2003-05-19
- Assignees: Global Locate, Inc.
- Applicants: Frank van Diggelen; Charles Abraham
- Inventors: Frank van Diggelen; Charles Abraham
- Web page: https://patentgrep.com/patent/US8571147B2

## CPC

- H04B 1/16: Circuits
- G01S 19/05: providing aiding data
- G01S 19/258: {relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view}
- G01S 19/26: involving a sensor measurement for aiding acquisition or tracking
- G01S 19/30: code related {(G01S19/246 takes precedence)}
- H04B 1/70754: {Setting of search window, i.e. range of code offsets to be searched (H04B1/70758 takes precedence)}
- H04B: TRANSMISSION
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## 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

### Claim 1

A method of correlating a digital communications signal from a satellite, comprising:
(a) defining a window equal to a portion of an epoch of said digital communication signal, wherein the portion corresponds to one of a plurality of portions that span the entire epoch;
(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 from other satellites in response to presence of said correlation peak, wherein said establishing comprises establishing the timing parameters based on a location of the window within the epoch.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

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

### Claim 6 (depends on 1)

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

### Claim 7 (depends on 1)

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

### Claim 8 (depends on 1)

The method of claim 1, wherein said defining step comprises: dividing said epoch into the plurality of portions; and selecting said portion from the plurality of portions.

### Claim 9 (depends on 1)

The method of claim 1, wherein the timing parameters include a local clock bias.

### Claim 10 (depends on 9)

The method of claim 9, wherein the local clock bias is determined to an accuracy of within a time duration of the window.

### Claim 11

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, wherein the portion corresponds to one of a plurality of portions that span the entire 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, wherein said establishing comprises establishing the timing parameters based on a location of the window within the predefined time period.

### Claim 12 (depends on 11)

The method of claim 11, wherein said predefined time period is one epoch of the GPS signal.

### Claim 13 (depends on 11)

The method of claim 11, 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.

### Claim 14 (depends on 11)

The method of claim 11, wherein said window is a half of the predefined time period.

### Claim 15 (depends on 11)

The method of claim 11, wherein said window is a quarter of the predefined time period.

### Claim 16 (depends on 11)

The method of claim 11, wherein said window is a third of the predefined time period.

### Claim 17

A method of establishing timing synchronization in a multi-channel GPS receiver, comprising:
(a) receiving a first GPS signal from a first GPS satellite using a first channel of the GPS receiver, where the first GPS signal repeats over a predefined time period;
(b) defining a window equal to a half of the predefined time period;
(c) correlating said first 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, wherein said establishing comprises establishing the timing parameters based on a location of the window within the predefined time period.

### Claim 18 (depends on 17)

The method of claim 17, further comprising:
(f) selecting another window equal to a second half of the predefined time period in response to absence of said correlation peak; and
(g) repeating steps (c), (d), (e), and (f) until said correlation peak is found.

### Claim 19

An apparatus for correlating a digital communication signal from a satellite, 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 from other satellites in response to presence of said correlation peak, wherein the microcontroller establishes the timing parameters based on a location of the window within the predefined time period.

### Claim 20 (depends on 19)

The apparatus of claim 19, wherein said correlator correlates said digital communication signal across another window within said predefined time period of said digital communication signal in response to absence of said correlation peak.

### Claim 21 (depends on 19)

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