%計算圓周卷積 
N=20;
N1=10;
N2=18;
n=0:1:N-1;
n1=0:1:N1-1;
n2=0:1:N2-1;
x1=(0.8).^n1;
x2=(0.6).^n2;
y=circonvt(x1,x2,N);
subplot(3,1,1),stem(n1,x1);
subplot(3,1,2),stem(n2,x2);
subplot(3,1,3),stem(n,y);