It is asked to graph time convolution using conv, filter, cconv and multiplication in frequency domain. All the answers seem to agree except the multiplication in frequency domain. What is wrong with it? Any suggestions?
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_n).*fft(y_n));
stem(n_ ,z);
xlabel('n')
xlim([-3,15])
title('u(n) * |2n+1|(u(n+1)-u(n-5)) multiplying in frequency domain')
Thanks
