MITIGATING MULTIPATH USING STATE TRANSITION DETECTION AND MEASUREMENT

• US 20130027245A1
• Filed: 07/26/2011
• Published: 01/31/2013
• Est. Priority Date: 07/26/2011
• Status: Active Grant

• Current Assignee: Qualcomm technologies international, ltd. (Qualcomm, Inc.)
• Original Assignee: Cambridge Silicon Radio Limited (Qualcomm, Inc.)
• Inventors: Lennen, Gary
• Granted Patent: US 8,599,067 B2
• Time in Patent Office: Days
• US Class Current: 342/357.25
• CPC Class Codes: G01S 19/22 Multipath-related issues

Abstract

A global positioning satellite (GPS) receiver that includes a radio frequency (RF) receiver receiving a first GPS signal from a GPS satellite and a processor. The processor is configured to correlate the first GPS signal with a plurality of reference signals to produce a plurality of correlations, detect a transition between receiving the first GPS signal and receiving a second GPS signal from the GPS satellite based on a phase shift in the correlations, and if the transition is detected, compensate for the phase shift when computing a range to the GPS satellite.

Claims

1. A global positioning satellite (GPS) receiver, including:

a radio frequency (RF) receiver receiving a first GPS signal from a GPS satellite; and

a processor configured to;

a) correlate the first GPS signal with a plurality of reference signals to produce a plurality of correlations,

b) detect a transition between receiving the first GPS signal and receiving a second GPS signal from the GPS satellite based on a phase shift in the correlations, and

c) if the transition is detected, compensate for the phase shift when computing a range to the GPS satellite.

2. The GPS receiver of claim 1,

wherein the processor determines the phase shift by interpolating the correlations.

3. The GPS receiver of claim 2,

wherein the processor interpolates the correlation to determine a corrective phase shift that results in an equivalent early correlation value and a late correlation value.

4. The GPS receiver of claim 1,

wherein if the transition is detected, the processor converts the phase shift to a distance, and subtracts the distance from the computed range from the GPS satellite to the GPS receiver.

5. The GPS receiver of claim 1,

wherein if the transition is detected, when the processor computes a location of the GPS receiver based on GPS signals received from the GPS satellite and a plurality of other GPS satellites, the processor weights a contribution of the GPS satellite in the location computation based on the phase shift.

6. The GPS receiver of claim 1,

wherein if the transition is detected, the processor immediately compensates for the phase shift.

7. The GPS receiver of claim 1,

wherein if the transition is detected, the processor filters the phase shift, and gradually increases the compensation for the phase shift over a time period.

8. A global positioning satellite (GPS) receiver, including:

a radio frequency (RF) receiver receiving a respective GPS signal from each of a plurality of GPS satellites; and

a processor is configured to;

a) correlate, for each GPS satellite, the respective GPS signal with a plurality of respective reference signals to produce a plurality of correlations,

b) detect, for each GPS satellite, a transition between receiving a first GPS signal and receiving a second GPS signal based on a phase shift in the correlations, and

c) if the transition is detected for a respective GPS satellite, compensate for the phase shift when computing a range to the respective GPS satellite.

9. The GPS receiver of claim 8,

wherein the processor determines the phase shift for each GPS satellite by interpolating the correlations for each GPS satellite.

10. The GPS receiver of claim 8,

wherein the processor interpolates each of the correlations to determine a corrective phase shift that results in an equivalent early correlation value and a late correlation value.

11. The GPS receiver of claim 8,

wherein if a transition is detected for a respective GPS satellite, the processor converts the phase shift to a distance, and subtracts the distance from the computed range from the respective GPS satellite to the GPS receiver.

12. The GPS receiver of claim 8,

wherein if the transition is detected for a respective GPS satellite, when the processor computes a location of the GPS receiver based on the GPS signals received from the plurality of GPS satellites, the processor compensates for the phase shift by weighting a contribution of the respective GPS satellite in the location computation based on the phase shift.

13. The GPS receiver of claim 8,

wherein if the transition is detected, the processor immediately compensates for the phase shift.

14. The GPS receiver of claim 8,

wherein if the transition is detected, the processor filters the phase shift, and gradually increases the compensation for the phase shift over a time period.

15. The GPS receiver of claim 8,

wherein the processor compares the phase shift to a threshold, and detects the transition when the phase shift is greater than the threshold.

16. A global positioning satellite (GPS) receiver, including:

a radio frequency (RF) receiver receiving a first GPS signal from a GPS satellite; and

a processor configured to;

a) correlate the first GPS signal with a plurality of reference signals to produce a plurality of correlations,

b) interpolate the correlations to determine a phase shift for balancing an early correlation and a late correlation value of the plurality of correlations,

c) compare the phase shift to a threshold,

d) detect a transition between receiving the first GPS signal and receiving a second GPS signal from the GPS satellite if the phase shift is greater than the threshold, and

e) if the transition is detected, compensating for the phase shift when computing a range to the GPS satellite.

17. The GPS receiver of claim 16,

wherein before interpolating the correlations, the processor shifts the correlations by an integer value to position a peak correlation at a specific correlation location.

18. The GPS receiver of claim 16,

wherein the processor interpolates the correlations using a cubic interpolation algorithm that produces polynomial coefficients for determining a phase shift to balance the early and late correlation values, and

wherein the processor iteratively computes the polynomial coefficients N times to fractionally shift the early and late correlation values around the peak correlation value, the fractional shift decreasing with each iteration.

19. The GPS receiver of claim 16,

wherein before comparing the phase shift to the threshold, the processor adjusts the threshold inversely proportionally with respect to a measured carrier to noise ratio (CNO) for the GPS signal.

20. The GPS receiver of claim 16,

wherein, when the processor computes a location of the GPS receiver based on GPS signals received from the GPS satellite and a plurality of other GPS satellites, if the transition is detected, the processor converts the phase shift to a distance value and weights a contribution of the GPS satellite in the location computation inversely proportionally to the distance value.