小波降噪在微弱GPS信号捕获中的应用

为了解决微弱卫星环境下接收机对信号的正确捕获问题，首先介绍微弱GPS信号捕获特点及捕获方法，并从检测概率和灵敏度的角度分析了相关积分、差分累加方法的捕获性能。在此基础上引入了小波降噪与相关积分、差分累加相结合的捕获方法，并给出详细的理论推导和捕获性能分析，从小波基的选取、小波变换层数和阈值选择三方面进行深入分析，从而得出合适的小波阈值降噪方法。考虑到小波降噪的阈值应跟据变换尺度不同而分别选取，给出一种自适应阈值降噪方法。实验证明，相比传统的相关积分、非相干累加和相关积分、差分累加信号捕获方法，小波降噪方法的引入在保证较高检测概率的同时，可以有效提高微弱卫星信号捕获的输出信噪比，从而降低了误码率。

Application of wavelet de-noising in weak satellite signal acquisition

The characteristic of weak global positioning system (GPS) signal acquisition is first analyzed and the coherent correlation and differential coherent accumulation methods are evaluated from the views of detection possibility and acquisition sensitivity. Based on those foundations, a method of wavelet de noising combined with coherent correlation and differential coherent accumulation is introduced with a detailed theoretical inference and characteristic analysis from three aspects. Experiment results show that compared with traditional coherent correlation and non coherent accumulation or differential coherent accumulation, the method with wavelet de noising can keep higher detection possibility and obtain larger acquisition output signal to noise ratio, thus the error bit rate is decreased efficiently.