Multipath processing for GPS receivers
First Claim
1. In a GPS receiver, a method for tracking signals comprising:
- tracking a first signal as an initial prompt signal using a local code replica at a first code delay;
detecting a second signal at a second code delay substantially earlier than the local code replica of the first code delay; and
adjusting the first code delay to track the second signal as a new prompt signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A GPS receiver system determines the presence of trackable signals at code delays less than the prompt delay being tracked for a particular signal and changes the prompt delay to correspond to the smallest code delay having a trackable signal. Trackable signals at large code delays are multipath signals and may be separately tracked to aid in dead reckoning. The trackable signals at code delays not adjacent to the currently tracked prompt delay may be tracked in the same channel as the prompt delay so that all satellite channels are continuously evaluated for multipath signals being tracked or a non-satellite specific channel may be used to sequentially step through the satellite signals to evaluate multipath on a satellite by satellite basis.
185 Citations
20 Claims
-
1. In a GPS receiver, a method for tracking signals comprising:
-
tracking a first signal as an initial prompt signal using a local code replica at a first code delay;
detecting a second signal at a second code delay substantially earlier than the local code replica of the first code delay; and
adjusting the first code delay to track the second signal as a new prompt signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
for each of the second signals, comparing the magnitude of the second signal to the magnitude of the first signal; and
adjusting the first code delay to track the second signal havinig the greatest magnitude.
-
-
4. The method of claim 1 further comprising:
-
identifying the initial prompt signal as a multipath signal; and
tracking the multipath signal to derive information.
-
-
5. The method of claim 4 wherein tracking the multipath signal comprises measuring the rate of change of the code delay of the at least one multipath signal.
-
6. The method of claim 5 wherein tracking the multipath signal further comprises estimating changes in the code delay of the direct path signal by monitoring the code delay of the multipath signal.
-
7. The method of claim 4 wherein tracking the multipath signal comprises:
-
monitoring the delay between the new prompt signal and the multipath signal;
when the delay is within 1.5 chips, modeling the correlation products for the multipath signal; and
compensating for the modeled correlation product.
-
-
8. The method of claim 7 wherein compensating for the modeled correlation product comprises subtracting the modeled correlation from the new prompt signal correlation.
-
9. A GPS receiver comprising:
-
means for tracking a first signal as an initial prompt signal using a local code replica at a first code delay;
means for detecting a second signal at a second code delay substantially earlier than the local code replica of the first code delay; and
means for adjusting the first code delay to track the second signal as a new prompt signal. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
means for comparing the magnitude of the each of the second signals to the magnitude of the first signal; and
means for adjusting the first code delay to track the second signal having the greatest magnitude.
-
-
12. The receiver of claim 9 further comprising means for tracking the initial prompt signal as a multipath signal to derive information.
-
13. The receiver of claim 12 wherein means for tracking comprises means for measuring the rate of change of the code delay of the at least one multipath signal.
-
14. The receiver of claim 13 wherein means for tracking further comprises means for estimating changes in the code delay of the direct path signal by monitoring the code delay of the multipath signal.
-
15. The receiver of claim 12 wherein means for tracking the multipath signal comprises:
-
means for monitoring the delay between the new prompt signal and the multipath signal;
means for modeling the correlation products for the multipath signal when the delay is within 1.5 chips; and
means for compensating for the modeled correlation products.
-
-
16. The receiver of claim 15 wherein means for compensating for the modeled correlation products comprises means for subtracting the modeled correlation from the new prompt signal correlation.
-
17. A GPS receiver comprising:
-
means for tracking a first signal using a local code replica at a prompt delay;
means for detecting the presence of signals at code delays less than the local code replica of the prompt delay; and
means for changing the prompt delay to track a selected one of the detected signals. - View Dependent Claims (18, 19, 20)
-
Specification