SYSTEM AND METHOD FOR FAST CODE PHASE AND CARRIER FREQUENCY ACQUISITION IN GPS RECEIVER

摘要

A GPS receiver (301) acquires carrier frequency and Gold code phase using short segments of a received GPS signal. In one embodiment, a 1-ms segment of the GPS signal is transformed to the frequency domain. This is multiplied (404) by a frequency representation of the Gol code (402). The resulting product is converted to the time domain, and a peak (406a-d) is detected. The location of the peak (406a-d) corresponds to the code phase. If no peak(406a-d) is located, the carrier frequency is changed. Full- and half-bin steps in carrier frequency are considered. Processing gain is achieved by using longer segments of the input signal, for example 4 or 16 ms and integrating 1 -ms segments. Considerations are provided for compensating for the effects of a transition, should it occur in the short segment of the GPS signal being processed. Integrations can be performed using non-coherent and coherent techniques. Adjustments are made for non-integral millisecond segment lengths.