Fast Acquisition of GPS Signal Using Radix-2 and Radix-4 FFT Algorithms

摘要

Acquisition is the important frontend operation of a GPS receiver signal processing. It estimates Doppler change in carrier frequency and delay in PRN code of the GPS signal and gives for tracking of signal. Tracking refines the Doppler shift and delay in code phase and removes the carrier, PRN code from the received GPS signal and acquires the navigational data. The performance of tracking directly depends on performance of acquisition algorithm. Performance of acquisition is compromise between computational time and Doppler frequency resolution. So this paper presents fast acquisition of Doppler shift and code phase from GPS Intermediate Frequency (IF) signal using radix4 and radix2 FFT algorithms. Performance of these acquisition algorithms is compared with time domain correlation and also with signal acquisition using radix2 FFT on decimated with zero padded data. Computational time and correlation magnitude are taken as metrics to evaluate the performance of the algorithms.