基于一种改进EMD算法的GPS多径效应抑制方法

摘要

An improved filter method based on EMD is proposed to mitigate the multipath effects in short baseline double-difference GPS observation. Noise-assist data analysis is adopted to compress the noise for low-order intrinsic mode function (IMF) after analyzing thepropagation ofnoise in EMD. Signal-to-noise ratio (SNR) of the higher order IMF is increased which improves the accuracy of the EMD decomposition. A new threshold de-noising method is developed based on the proposed EMD algorithm. By altering in a random way the position of the samples of the first IMF, different noise versions of the original signal are obtained, and the position sensitive error of EMD is mitigated by averaging the multiple de-noising results. A comparative evaluation is made on simulation signals among wavelet de-noising method, conventional EMD threshold de-noising and our proposed method, and the results show that our proposed method outperforms the other two. At last, the method is applied in short baseline double difference GPS observation to separate the multipath errors and the results show that the new method is effective.%为了抑制短基线双差分GPS测量中的多径误差，提出了一种改进的经验模态分解(EMD)滤波方法。首先分析了含噪信号EMD分解的噪声传播特性，提出应用噪声辅助数据分析方法对低阶模态分量进行处理，实现将信号的噪声压缩至低阶本征模态函数(IMF)中，进而提高含噪信号高阶模态分量的信噪比。然后基于上述改进的EMD算法实现了模态单元阈值降噪，随机采样第1阶IMF构造多个具有相同信噪比的序列，最后平均处理多个序列的降噪结果以消除EMD分解的位置敏感性误差，与小波降噪以及传统EMD阈值降噪的仿真对比表明，提出的降噪算法有显著优势。最后，将提出的算法用于GPS测量信号的多径误差提取，结果表明该方法可以用于抑制短基线GPS测量的多径误差。