Application of Fast FFT Acquisition Algorithm in GPS C/A and P(Y) Codes

FFT can be used to operate on a block of inputting intermediate frequency(IF) sequences and local replica pseudo code sequences through providing parallel search pseudo code phases.It is a fast and efficient acquisition approach for GPS signals.This paper analyzes the implementation of circular correlation using FFT and FFT application in fast acquisition of GPS C/A codes,realizes the fast direct P(Y) codes acquisition by using full interval correlation,extended replica code folding,overlap and adds,overlap and discard approaches.The problem of FFT operation points can be solved through zero padding,linear interpolation,Sinc interpolation,averaging correlation and double-length zero-padding.Moreover,such problems as the phase reversal caused by navigation data,linear correlation operation between extra long sequences and short sequences,linear correlation implementation using circular correlation in application can be solved by extending FFT operation points.