对代码进行注释%循环卷积 x1=[1 2 3 2]; x2=[2 1 2 1]; xn1=length(x1); xxn1=0:xn1-1; subplot(2,1,1); stem(xxn1,x1,'.','b'); title('序列x1'); axis([-1,4,0,4]);grid; xn2=length(x2); xxn2=0:xn2-1; subplot(2,1,2); stem(xxn2,x2,'.','b'); title('序列x2'); axis([-1,4,0,4]);grid; figure(2) N=4; x1=[x1,zeros(1,N-length(x1))]; x2=[x2,zeros(1,N-length(x2))]; m=0:N-1; x=zeros(N,N); for n=0:N-1 x(:,n+1)=x2(mod((n-m),N)+1); end; yn=x1*x; subplot(3,1,1); stem(m,yn,'b','.'); title('序列x1和序列x2的4点循环卷积结果'); axis([-1,4,0,15]);grid; N=7; x1=[x1,zeros(1,N-length(x1))]; x2=[x2,zeros(1,N-length(x2))]; m=0:N-1; x=zeros(N,N); for n=0:N-1 x(:,n+1)=x2(mod((n-m),N)+1); end; yn=x1*x; subplot(3,1,2); stem(m,yn,'b','.'); title('序列x1和序列x2的7点循环卷积结果'); axis([-1,7,0,15]);grid; N=8; x1=[x1,zeros(1,N-length(x1))]; x2=[x2,zeros(1,N-length(x2))]; m=0:N-1; x=zeros(N,N); for n=0:N-1 x(:,n+1)=x2(mod((n-m),N)+1); end; yn=x1*x; subplot(3,1,3); stem(m,yn,'b','.'); title('序列x1和序列x2的8点循环卷积结果'); axis([-1,8,0,15]);grid;

好的，以下是对代码的注释：

% 循环卷积

% 定义两个序列 x1 和 x2
x1=[1 2 3 2];
x2=[2 1 2 1];

% 画出序列 x1 和 x2
xn1=length(x1);
xxn1=0:xn1-1;
subplot(2,1,1);
stem(xxn1,x1,'.','b');
title('序列x1');
axis([-1,4,0,4]);grid;

xn2=length(x2);
xxn2=0:xn2-1;
subplot(2,1,2);
stem(xxn2,x2,'.','b');
title('序列x2');
axis([-1,4,0,4]);grid;

% 对 x1 和 x2 进行循环卷积
figure(2)

% 对于 N=4
N=4;
x1=[x1,zeros(1,N-length(x1))];
x2=[x2,zeros(1,N-length(x2))];
m=0:N-1;
x=zeros(N,N);
for n=0:N-1
    x(:,n+1)=x2(mod((n-m),N)+1);
end;
yn=x1*x;
subplot(3,1,1);
stem(m,yn,'b','.');
title('序列x1和序列x2的4点循环卷积结果');
axis([-1,4,0,15]);grid;

% 对于 N=7
N=7;
x1=[x1,zeros(1,N-length(x1))];
x2=[x2,zeros(1,N-length(x2))];
m=0:N-1;
x=zeros(N,N);
for n=0:N-1
    x(:,n+1)=x2(mod((n-m),N)+1);
end;
yn=x1*x;
subplot(3,1,2);
stem(m,yn,'b','.');
title('序列x1和序列x2的7点循环卷积结果');
axis([-1,7,0,15]);grid;

% 对于 N=8
N=8;
x1=[x1,zeros(1,N-length(x1))];
x2=[x2,zeros(1,N-length(x2))];
m=0:N-1;
x=zeros(N,N);
for n=0:N-1
    x(:,n+1)=x2(mod((n-m),N)+1);
end;
yn=x1*x;
subplot(3,1,3);
stem(m,yn,'b','.');
title('序列x1和序列x2的8点循环卷积结果');
axis([-1,8,0,15]);grid;

希望这些注释能够帮助你更好地理解这段代码的实现过程。