子波域自适应滤波方法

 推导和给出了噪声能量阈值的理论计算公式，并提出了一种实时估计信号噪声方差的有效方法，从而构成形式完整和实用的自适应相关计算子波阈滤波算法。仿真计算和分析表明：给出的方法具有良好的自适应性能和显著的滤波效果，在有效去除噪声的同时，很好保留了信号的主要细节。

ADAPTIVE FILTERING IN WAVELET TRANSFORM DOMAIN

A complete adaptive algorithm of denoising by wavelet transforms was developed, which has been presented by Xu,et al.The primary idea is that the wavelet transforms of signals are deeply correlated at several adjacent scales, while the noise is not. The form of noise standard deviation at each scale was given here,and then a method is presented to select the power threshold of noise. An effective standard deviation estimation of noise involved in a true signal was also described here, which was based on the fact that in fine scales wavelet transforms are dominated by noise. The two finest scales are correlated to estimate noise covariance better. The simulation shows that while getting rid of noise mostly, this algorithm keeps the main edges of signal well.