exa4_13.m

来自「噪声及波形信号的产生,包括square函数,sawtooth函数,chirp函数」· M 代码 · 共 19 行

% exa4-12_butterstopDF.m , for example 4-12
% using butterworth to design bandstop DF

clear all;
Wp=[0.4*pi,0.7*pi];
Ws=[0.2*pi,0.8*pi];
Ap=1;
As=30;
[N,wn]=buttord(Wp/pi,Ws/pi,Ap,As); %计算巴特沃斯滤波器阶次和截止频率
[b,a]=butter(N,wn,'stop'); %频率变换法设计巴特沃斯带通滤波器
[C,B,A]=dir2cas(b,a)  %数字高通滤波器级联型
[db,mag,pha,grd,w]=freqz_m(b,a); %数字滤波器响应
subplot(211);
plot(w/pi,mag);
title('数字滤波器幅频响|H(ejOmega)|')
subplot(212);
plot(w/pi,db);
title('数字滤波器幅频响(dB)')