一种基于快速傅里叶变换和圆周移位的捕获算法

An Acquisition Algorithm Based on FFT and Circular Shifting

信号搜索捕获是影响GPS软件接收机的重要工作性能指标。为了提高GPS软件接收机的捕获速度,提出了一种基于快速傅里叶变换(FFT)和圆周移位的捕获算法。该算法利用圆周移位的性质,即时域序列的调制等效于频域的圆周移位,将中频信号频谱序列通过圆周移位得到基带频谱序列,不用再通过载波分离,从而降低FFT运算次数。理论分析表明该算法可以有效减少运算量,提高捕获性能。最后,通过FPGA与DSP搭建仿真实验平台,将该捕获算法与已有算法进行比较,结果表明该算法具有较快的捕获速度,减少了捕获时间。

Signal acquisition makes an important influence on the working performance of GPS software receiver.In order to improve the acquisition speeding of GPS software receiver,an acquisition algorithm based on FFT and circular shifting is proposed.The algorithm is proposed based on the principle of circular shifting that the modulation of the time-domain sequence is equal to the circular shifting operation in frequency-domain.The sequence of IF signal spectrum is converted into the baseband spectrum by the circular shifting,no longer by the carrier wipeoff,thereby reducing the number of FFT operation.The theoretical analysis shows that the algorithm can effectively reduce the amount of computation to improve the acquisition performance.Finally,the proposed acquisition algorithm is compared with the existing algorithm through the simulation platform built by FPGA and DSP.The results show that the algorithm has faster acquisition speed and reduces acquisition time.