convolve two signals using coonv, filter, cconv, freq domain multiplication (this one gives a wrong answer)

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DDD 2015-5-26

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/218793-convolve-two-signals-using-coonv-filter-cconv-freq-domain-multiplication-this-one-gives-a-wrong

评论： Matt J 2015-5-26

only the last one is not giving me an equal answer.

u=@(n)1.0.*(n>=2);
y=@(n)abs(2.*n+1).*(u(n+1)-u(n-5));
n_x=1:10;
n_y=-2:20;
y_n=u(n_y);
x_n=y(n_x);
c=conv(x_n,y_n);
n_c= n_x(1)+n_y(1):n_x(end)+n_y(end);
figure()
%
subplot(4,1,1)
stem(n_c,c)
xlabel('n')
xlim([-3,15])
title('u(n)  *  |2n+1|(u(n+1)-u(n-5)) using conv')
%
cf=filter(x_n,1,y_n);
cf=[cf,zeros(1,length(n_c)-length(cf))];
subplot(4,1,2)
stem(n_c,cf)
xlabel('n')
xlim([-3,15])
title('u(n)  *  |2n+1|(u(n+1)-u(n-5)) using filter')
% 
cc=cconv(y_n,x_n);
subplot(4,1,3)
stem(n_c,cc)
xlabel('n')
xlim([-3,15])
title('u(n)  *  |2n+1|(u(n+1)-u(n-5)) using cconv')
subplot(4,1,4)
z=ifft(fft(x(-2:20)).*fft(y(-2:20)));
stem(-2:20 ,z);
xlabel('n')
title('u(n)  *  |2n+1|(u(n+1)-u(n-5)) multiplying in frequency domain')