一种改善GNSS弱信号动态跟踪性能的FFT鉴频方法

A FFT frequency discriminator for improving the dynamic tracking performance of GNSS weak signal

基于快速傅里叶变换(FFT)鉴频器的GNSS弱信号跟踪技术可以有效改善城市峡谷环境的行人导航,然而现有的复数平方FFT(SFFT)鉴频器在车载等较高动态应用中弱信号跟踪性能大幅度下降。本文提出了一种在保证弱信号跟踪灵敏度的前提下,能显著提高动态性能的FFT鉴频方法——非相干FFT鉴频器(NonCoh-FFT)。首先,介绍了SFFT鉴频器和NonCoh-FFT鉴频器的结构原理;然后,从理论上分析了两者的灵敏度和动态性能;最后,基于GNSS信号模拟器产生的静态和动态场景,对比测试验证了SFFT和NonCoh-FFT性能。结果表明,NonCoh-FFT可以明显提高GNSS弱信号动态性能,与理论分析吻合。

The GNSS weak signal tracking technology based on the FFT frequency discriminator can effectively improve pedestrian navigation in urban canyon environment;however,the weak signal tracking ability of existing Complex Squared FFT（SFFT）discriminators would be greatly reduced in vehicles and other high dynamic applications.On the premise of ensuring the sensitivity of weak signal tracking,a Non-Coherent FFT（NonCoh-FFT）frequency discrimination is proposed,which can significantly improve dynamic performance.First,the structure principle of the existing SFFT frequency discriminator and the proposed NonCoh-FFT frequency discriminator are analyzed.Then,the sensitivity and dynamic performance of the two discriminators are analyzed theoretically.Finally,based on the static and dynamic scenes of the GNSS signal simulator,the SFFT and NonCoh-FFT are compared and tested.The results show that the NonCoh-FFT can obviously improve the dynamic performance of the GNSS weak signal,which is consistent with the conclusion of theoretical analysis.