Optimized PFA algorithm in GPS software receiver

According to the specific storage mode of GPS data,a novel algorithm using 2-bit to quantitate the GPS data and the local carrier signal was proposed,and the baseband-mixing operation was transformed into bit-wise calculation,then the result was set as the input data of PFA algorithm.Part of the twiddle factors were pre-stored as 16-bit complement integer,and the whole factors were generated by mapping strategy when used.So all the floating-point calculations were transformed into integer operations.Experimental results show that this method has improved the efficiency of the PFA algorithm significantly,and the acquisition time were reduced effectively.