butterworth.asv

来自「滤波器的MATLAB实现程序 内附多个源代码」· ASV 代码 · 共 51 行

clear all
close all
clc
n=0:0.01:2;

As=50;
Ap=0.5;
typeo=4;
switch typeo
case 1
    type='bandpass';
case 2
    type='stop';
case 3
    type='high';
case 4
    type='low';
end
if typeo==1
Wp=[0.4*pi,0.8*pi];
Ws=[0.3*pi,0.9*pi];
elseif typeo==2
Ws=[0.4*pi,0.8*pi];
Wp=[0.3*pi,0.9*pi];   
elseif typeo==3 
    Wp=0.6*pi;
    Ws=0.5*pi;
elseif typeo==4
     Wp=0.6*pi;
    Ws=0.7*pi;
end
[N,wn]=buttord(Wp/pi,Ws/pi,Ap,As);
[b,a,k]=butter(N,wn,type,'s');
[b,a]=zp2tf(b,a,k);
[H,w]=freqs(b,a,n);
H1=abs(H);
H2=db(H1);
b=find(w>=0.7&w<0.71);
m=H2(b)
subplot(211)
plot(w,H1)
xlabel('f');
ylabel('|H(jw)|')
title('Butterworth滤波器')
grid
subplot(212)
plot(w,angle(H))
grid
xlabel('f');
ylabel('phase')