exa4_11.m

matlab应用实例。如：FIR、IIR数字滤波器设计等。

% exa4-11_butterbandDF.m , for example 4-11
% using butterworth to design bandpass DF

clear all;
Wp=[0.3*pi,0.4*pi];
Ws=[0.2*pi,0.5*pi];
Ap=3;
As=18;
[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,'bandpass'); %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)')