Patent ID: 7545894

Claim:
A method for use in the acquisition of a location system signal, the location system signal including a first data signal and a second data signal superimposed on the first data signal, the method comprising: a) generating an initial Doppler frequency offset value, the Doppler frequency offset representing a variance from a nominal frequency for the location system signal and a frequency of a received location system signal; b) using the initial Doppler frequency offset value and at least one other Doppler frequency offset value to generate a plurality of error signals, each error signal representing a difference between a sum of consecutive correlation values and a corresponding estimated ideal value, each error signal corresponding to a different time offset and an associated time period in which the consecutive correlation values pertain, the second data signal having a bit edge during the time period of each of at least some of the sums of consecutive correlation values, and wherein a bit transition at the bit edge causes an increase in the error signal when the bit edge occurs during the associated time period; c) identifying a time offset value wherein a measure of the error signal is minimal, the identified time offset value identifying the bit edge; d) employing the identified time offset value to obtain a first determined Doppler frequency value; and e) using a Kalman filter to generate a refined Doppler frequency offset value based at least in part on the first determined Doppler frequency value.