sy3.m

心电图滤波

clear;clc;
%输入的心电图采样信号
x=[-4,-2,0,-4,-6,-4,-2,-4,-6,-6,-4,-4,-6,-6,-2,6,12,8,0,-16,-38,-60,-84,-90,-66,-32,-4,-2,-4,8,12,12,10,6,6,6,4,0,0,0,0,0,-2,-4,0,0,0,-2,-2,0,0,-2,-2,-2,-2,0];
%下面是Hz
A=[0.09036 2*0.09036 0.09036];
B1=[1 -1.2686 0.7051];
B2=[1 -1.0106 0.3583];
B3=[1 -0.9044 0.2155];
[H1,w]=freqz(A,B1,100);
[H2,w]=freqz(A,B2,100);
[H3,w]=freqz(A,B3,100);
H=H1.*H2.*H3;
mag=abs(H);
db=20*log((mag+eps)/max(mag));
figure;
plot(w/pi,db,'r');axis([0,0.5,-50,10]);title('滤波器的幅频特性曲线');

y=filter(A,B3,filter(A,B2,filter(A,B1,x)));%滤波实际上就是卷积的过程
figure;
subplot(2,1,1);stem (x,'r.');axis([0,56,-100,50]);title('心电图波形');
subplot(2,1,2);stem (y,'r.');axis([0,56,-100,50]);title('滤波后');