MATLAB实例：四阶Butterworth滤波器设计与应用

clear;clc; fs=2000; %采样频率 T=1/fs; L=500; t=(0:L-1)*T; y1=sin(2*pi*200*t); y2=0.5*sin(2*pi*400*t); y3=0.1*sin(2*pi*600*t); y=y1+y2+y3; %低通滤波器 fc=300; wn=2*fc/fs; [b,a]=butter(4,wn,'low');%构造butterworth低通滤波器，保留频率低于300Hz的振动 y_low=filter(b,a,y); figure();plot(y_low,'r');hold on;plot(y1,'k') xlabel('Time');ylabel('Amplitude')

%高通滤波器 fc=590; wn=2*fc/fs; [b,a]=butter(4,wn,'high');%保留频率高于590Hz的振动 y_high=filter(b,a,y); figure();plot(y_high,'r');hold on;plot(y3,'k') %带通滤波器 [b,a]=butter(4,[300*2/fs 590*2/fs]); %保留频率高于300低于590Hz的振动 yy=filter(b,a,y); figure();plot(yy,'r');hold on;plot(y2,'k')