优化的PFA算法在GPS软件接收机中的应用

Optimized PFA algorithm in GPS software receiver

根据GPS数据的特殊存储结构,提出了一种2bit量化的方式来表示导航数据以及本地载波,将基带混合过程演化为位运算过程,结果作为PFA算法的输入;将PFA算法中用到的部分旋转因子转换为16bit补码预存到数据表,使用时通过映射的方式得到全部旋转因子,因此PFA算法中所有的浮点运算都被转化为了整数运算方式,实验表明此方法大幅提升了PFA算法的效率,进而有效缩短了捕获时间。

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 comple-ment 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.