GNSS弱信号两级快速傅里叶变换捕获方法

Weak GNSS Signals Acquisition Algorithm Using Two-stage FFT

高动态弱信号条件下,为了提高捕获过程实现的灵活性,提出了两级快速傅里叶变换(FFT)多普勒频率捕获方法,第一级FFT使用较短的相干积分时间将多普勒频率搜索范围划分为多个粗分格,第二级FFT在每一个分格内对多普勒频率进行更精细的搜索。采用文章提出的捕获方法,可以降低FFT点数,简化实现复杂度;另一方面,计算第一级FFT时可通过流水线操作提高资源利用率。为了验证所提方法的正确性,仿真实现了两级FFT捕获方法。结果表明,两级FFT方法能在高动态弱信号条件下正确捕获多普勒频率。

To improve the implementation flexibility of GNSS weak signal acquisition in the high dynamic environments, an acquisition algorithm including two-stage fast Fourier transform （FFT） was developed. In the first stage, the short coherent integration time was employed to divide the Doppler frequency range into several sub-ranges called coarse Doppler frequency bins. In the second stage, the fine Doppler frequency searching was completed based on the output of the first stage FFT. The presented method can reduce the number of FFT points and the implementation complexity. Besides, the pipeline processing was used in the first stage FFT, which could increase the efficiency of hardware source. The simulation results show that the presented method can acquire weak GNSS signals correctly in high dynamic scenarios.