一种高动态低信噪比卫星导航信号捕获方法

为提升高动态低信噪比环境下卫星导航信号的捕获性能,提出了一种基于分数阶傅里叶变换(FrFT)及部分匹配滤波(PMF)的捕获方法。在该方法中,接收机首先利用PMF对接收信号做分段相干积分,随后借助快速傅里叶变换(FFT)对分段积分结果做离散快速FrFT,最后通过检测FrFT输出的峰值完成信号的捕获。由于具有多普勒频率变化率的卫星导航信号在FrFT后呈现能量聚焦特性,所提方法能够显著提高信号的长时间相干积分增益。同时对所提算法的捕获概率、平均捕获时间以及算法复杂度等性能指标进行了理论分析及计算机仿真验证。仿真表明,与传统的PMF-FFT方法相比,所提方法能够通过延长相干积分时间的方式有效提升高动态低信噪比卫星导航信号的捕获概率、降低捕获时间。

An Acquisition Algorithm for High Dynamic and Low SNR GNSS Signals

To improve the acquisition performance of the high dynamic and low signal noise ratio (SNR) global navigation satellite system (GNSS) signals, a new acquisition algorithm based on fractional Fourier transform (FrFT) and partially matched filter (PMF) is proposed. With the proposed approach, the received signals are first addressed by the PMF, and then the PMF outputs are processed by the FrFT that can be realized by the fast Fourier transform (FFT). As a result, the signal acquisition can be completed by the peak detection of the FrFT outputs. Since the Doppler rate of the received GNSS signals can be estimated by the FrFT, the long-time coherent integration gain can be greatly improved by this approach. Meanwhile, the acquisition probability, mean acquisition time and computation complexity are analysed theoretically and verified through computer simulation. The simulation results show that, compared with the traditional PMF-FFT method, the presented algorithm can effectively improve the acquisition probability of the high-dynamic low-SNR GNSS signals and shorten the acquisition time by extending the coherent integration time.