说明：   1.分析并了解巴特沃斯滤波器的频率特性 2.设计一个巴特沃斯滤波器使它符合对应的要求 3.学习绘制巴特沃斯滤波器的零极点分布图 4.通过设计对MATLAB的应用有了相应的了解 5.进一步了解截止频率和过渡带频率的范围等概念
(1、Analysis and understanding of the frequency characteristics of Butterworth filter 2、Design a Butterworth filter to make it comply with the requirements of the corresponding 3、Studying the zero-pole Butterworth filter drawn maps)