Two dimension direct GPS signal acquisition based on unsymmetrical FFT

As the typical CDMA application, the spread spectrum pseudorandom noise (PRN) codes in GPS are C/A code applied to standard positioning service and P code applied to precise positioning service presently. P code has a higher tolerance to jamming and spoofing compared with the C/A code, but P code is usually acquired depending on C/A code.In the precondition of good cross correlation and partial autocorrelation of P code, an improved direct P code acquisition algorithm based on unsymmetrical FFT and coherent accumulation is proposed and realized. Compared to conventional slipping correlation method, the time of novel direct P code acquisition algorithm is reduced more than ten times and the computational complexity is reduced rapidly. It´s also useful for other direct long PRN codes acquisition.