Matlab中的PAM平顶采样

Question

我不明白为什么我的代码在3秒钟的时间内没有正确回答，有人可以帮我看看犯罪的平顶采样（pam）模型吗？

fc = 10;    %carrier frequency
fm = 1;     % message frequency
fs = 1000;  % sampling frequency
t = 3;  
n = [0:1/fs:t];
n = n(1:end - 1);
duty = 20;
s = square(2*pi*fc*n,duty);
s(find(s<0)) = 0;
m = sin(2*pi*fm*n);
period_samp = length(n)/fc;
ind = [1:period_samp:length(n)];
on_samp = ceil(period_samp * duty/100);
pam = zeros(1,length(n));
for i = 1 : length(ind)
   pam(ind(i):ind(i) + on_samp) = m(ind(i));
end