Patent ID: 7864898
Filing Date: 2011-01-04
Classification: G01S

Abstract:
1. A method of processing signals from navigation satellites at a receiver, comprising: performing a learning process prior to signal acquisition to obtain a plurality of estimated values of signal-to-noise ratio, each estimated value of signal-to-noise ratio corresponding to an average signal power within an elevation band of a plurality of elevation bands defined within a range of elevation angles between the navigation satellites and the receiver; generating a different set of power threshold values for signal acquisition for each of the elevation bands, each power threshold value corresponding to a respective estimated value of signal-to-noise ratio such that a probability of desired signal detection is high and a probability of a false alarm detection is low for each signal received at the receiver that has an accumulated power greater than its corresponding power threshold value; receiving a down-converted received signal to be acquired from a transmitting satellite; correlating the down-converted received signal with a local replica signal to generate correlation values; integrating the correlation values of the received signal to generate its accumulated power; determining a current condition associated with the received signal based on an elevation band in which the transmitting satellite is located and noise level at the receiver; selecting a first power threshold value from the generated set of power threshold values using the determined current condition; comparing the accumulated power of the received signal with the first power threshold value; declaring signal acquisition when the accumulated power exceeds the first power threshold value; selecting a second power threshold value from the generated set of power threshold values when the accumulated power does not exceed the first power threshold value, wherein the second power threshold value is lower than the first power threshold value, and repeating the comparing and declaring steps using the second power threshold value.