work3.m

dsp学习中matlab试验源代码

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];
n=0:55;
subplot(2,2,1);
stem(n,x,'.');
axis([0 56 -100 50]);
title('心电图信号采样序列x（n）');

B=[0.09036 2*0.09036 0.09036];
A=[1.2686 -0.7051];
A1=[1.0106 -0.3583];
A2=[0.9044 -0.2155];
while(k<=3)
    y=filter(B,A,x);
    x=y;
   if k==2
       A=A1;
   end
   if k==3
       A=A2;
   end
  k=k+1;
end

n=0:55;
subplot(2,2,3);
stem(n,y,'.');
axis([0 56 -15 5]);
title('三级滤波后的心电图');

A=[0.09036,0.1872,0.09036];
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);

H4=H1.*(H2);
H=H4.*(H3);
mag=abs(H);
subplot(2,2,2);
plot(w/pi,mag);
axis([0,0.6,0,1.5]);
title('滤波器的幅频响应曲线');