Method and apparatus for improved L2 performance in dual frequency semi-codeless GPS receivers

• US 6,954,488 B1
• Filed: 11/12/1999
• Issued: 10/11/2005
• Est. Priority Date: 10/01/1999
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Lennen, Gary
• Primary Examiner(s): Bocure, Tesfaldet
• Assistant Examiner(s): Kumar, Pankaj
• Application Number:
  US09/439,608
• Time in Patent Office: 2,160 Days
• Field of Search: 375/375, 375/137, 375/354, 375/359, 375/368, 375/316, 375/136, 375/147, 375/149, 375/150, 375/340, 375/130, 342/48, 342/90, 342/95, 342/96, 342/99, 701/213, 701/214, 701/215, 701/207, 701/200, 34042618- 19, 340/426.1
• US Class Current: 375/149
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

This invention relates to improving the signal-to-noise ratio of semi-codeless tracking by presenting a method and apparatus which employs an optimal W-code timing pattern, and/or provides signal-to-noise gain by adding L1 and L2 W-code bit timing estimate signals before combining the L1 W-code estimate signal with the L2 W-code estimate signal.

Claims

1. An apparatus for tracking remotely generated signals comprising:

a first tracker for tracking a first component of a first remotely generated signal and including a W-code signal generator responsive to a second component of the first signal for locally generating a first W-code signal from said second component of the first signal; and

a second tracker for tracking a first component of a second remotely generated signal according to the first W-code signal;

wherein

the second component of the first signal has the same pattern as the first component of the second signal;

the pattern comprises a known pattern combined with an unknown pattern; and

the first tracker generates a first local component signal in accordance with the known pattern and combines the local component signal with a version of the first signal to generate the first W-code signal.

2. An apparatus for tracking remotely generated signals comprising:

a first tracker for tracking a first component of a first remotely generated signal and including a W-code signal generator responsive to a second component of the first signal for locally generating a first W-code signal from said second component of the first signal; and

a second tracker for tracking a first component of a second remotely generated signal according to the first W-code signal;

wherein

the second component of the first signal has the same pattern as the first component of the second signal;

the pattern consists a known pattern combined with an unknown pattern; and

the second tracker generates a second local component signal in accordance with the known pattern and combines the second local component signal with at least one version of the second signal to generate at least one second W-code signal.

3. An apparatus for tracking signals comprising:

a first tracker for tracking a first component of a first signal and for generating a first estimate signal from a second component of the first signal; and

a second tracker for tracking a first component of a second signal according to the first estimate signal;

wherein;

the second component of the first signal has the same pattern as the first component of the second signal;

the pattern comprises a known pattern combined with an unknown pattern;

the second tracker generates a second local component signal in accordance with the known pattern and combines the second local component signal with at least one version of the second signal to generate at least one second estimate signal; and

the second tracker generates a timing signal in accordance with the timing information for improving the accuracy of the at least one second estimate signal.

4. An apparatus for tracking signals comprising:

a first tracker for tracking a first component of a first signal and for generating a first estimate signal from a second component of the first signal; and

a second tracker for tracking a first component of a second signal according to the first estimate signal;

wherein

the second component of the first signal has the same pattern as the first component of the second signal;

the pattern comprises a known pattern combined with an unknown pattern;

the first tracker generates a first local component signal in accordance with the known pattern and combines the local component signal with a version of the first signal to generate the first estimate signal; and

the second tracker combines the first estimate signal with the at least one second estimate signal to provide a tracking signal for tracking the first component of the second signal.

5. An apparatus according to claim 4, wherein:

the second tracker combines the first estimate signal with the at least one second estimate signal to generate a combined estimate signal.

6. An apparatus according to claim 5, wherein:

the second tracker combines the first estimate signal with the at least one second estimate signal when the second tracker has not locked to the first component of the second signal; and

the second tracker combines the combined estimate signal with the at least one second estimate signal when the second tracker has locked to the first component of the second signal.

7. A method for tracking signals comprising the steps of:

locking to a first component of a first signal;

aligning a local version of a second component of the first signal with the first component of the first signal;

aligning a local version of a first component of a second signal with the first component of the first signal;

generating a first estimate signal from a version of the first signal and the local version of the second component;

applying the first estimate signal for locking to a first component of the second signal; and

wherein the second component of the first signal and the first component of the second signal comprise the same pattern.

8. A method for tracking signals comprising the steps of:

locking to a first component of a first signal;

aligning a local version of a second component of the first signal with the first component of the first signal;

aligning a local version of a first component of a second signal with the first component of the first signal;

generating a first estimate signal from a version of the first signal and the local version of the second component;

generating a second estimate signal from a version of the second signal and a local version of the first component of the second signal;

combining the second estimate signal and the first estimate signal to generate a combined estimate signal; and

selectively applying either the first estimate signal or the combined estimate signal for locking to a first component of the second signal; and

wherein the second component of the first signal and the first component of the second signal comprise the same pattern.

9. The method of claim 8, wherein the step of selectively applying further comprises the steps of:

Selecting the first estimate signal for application if the local version of the first component of the second component has not been locked; and

selecting the combined estimate signal for application if the local version of the first component of the second component has been locked.

10. A method of semi-codeless tracking for a GPS receiver comprising the steps of:

receiving a GPS L1 signal and generating at least a quadrature baseband version of the GPS L1 signal;

receiving a GPS L2 signal and generating baseband versions of the GPS L2 signal;

effecting a multiplication of the quadrature baseband version of the GPS L1 signal with a locally generated version of a P-code used to generate the Y-code component of both the GPS L1 and L2 signals, said multiplication generating a first estimate signal related to the W-code used with the P-code to generate the Y-code component;

multiplying the in-phase baseband version of the GPS L2 signal with a locally generated version of the P-code to generate a second estimate signal related to the W-code used with the P-code to generate the Y-code component;

adding the first W-code estimate signal to the second W-code estimate signal to generate a combined W-code estimate signal;

applying the first W-code estimate signal to generate tracking signals for tracking when the GPS receiver has not locked to the GPS L2 signal; and

applying the second W-code estimate signal to generate tracking signals for tracking when the GPS receiver has locked to the GPS L2 signal.

11. A method of semi-codeless tracking for a GPS receiver comprising the steps of:

receiving a GPS L1 signal and generating at least a quadrature baseband version of the GPS L1 signal;

receiving a GPS L2 signal and generating baseband versions of the GPS L1 signal;

effecting a multiplication of the quadrature baseband version of the GPS L1 signal with a locally generated version of a P-code used to generate the Y-code component of both the GPS L1 and L2 signals, said multiplication generating a first wide-band estimate signal related to the W-code used with the P-code to generate the Y-code component;

integrating the first wide-band estimate signal based on known timing information of the Y-code to generate a first narrow-band W-code estimate signal;

multiplying the in-phase baseband version of the GPS L2 signal with a locally generated version of the P-code to generate a second wide-band estimate signal related to the W-code used with the P-code to generate the Y-code component;

integrating the second wide-band estimate signal based on known timing information of the Y-code to generate a second narrow-band W-code estimate signal;

adding the first narrow-band W-code estimate signal to the second narrow-band W-code estimate signal to generate a combined W-code estimate signal;

applying the first narrow-band W-code estimate signal to generate tracking signals for tracking when the GPS receiver has not locked to the GPS L2 signal; and

applying the second narrow band W-code estimate signal to generate tracking when the GPS receiver has locked to the GPS L2 signal.