零相移滤波器的改进及实现方法

Improvement & Realization of the Zero-Phase Filter

基于数字信号处理的基本原理 ,本文提出了一种改进型的零相移滤波器的设计方法 .该方法把求解滤波器的初始状态和利用反射变换平滑信号的方法相结合 ,较好地消除了普通零相移滤波后信号的首尾波形畸变 .并介绍了一种采用 VC和 Matlab混合编程快速实现该滤波器的方法 .

In some practical applications, a zero phase filter is desirable to preserve the phase information of the original signal. The zero phase filter uses the information in the signal at points before and after the current point, in essence “looking into the future”, to eliminate the phase distortion. The filter performs zero phase digital filtering by processing input in both the forward and reverse directions. After filtering in the forward direction, it reverses the filtered sequence and runs it back through the filter. The resulting sequence has precisely zero phase distortion and double the filter order. In order to minimize start up and ending transients, we adjust initial conditions to match the DC component of signal and by prepending several filter lengths of a flipped, reflected copy of input signal, through analyzing its underlying principles. Moreover we introduce a method to realize the arithmetic fast with Matlab and Visual C++ 6.0. This filter has been used to process earthquake signals and yields satisfactory results.