I have a sinusiodal signal x in time domain.I have done the convlotion as followings using matlab: y=conv(x,x) and y=conv(x,fliplr(x)). Observing the result by Matlab, both of the above signal giving the same result in frequency domain. Why do you think is that?

P.S: FLIPLR(X) returns X with row preserved and columns flipped in the left/right direction.

X = 1 2 3     becomes  3 2 1
    4 5 6              6 5 4

Convolution in the time domain means you are multiplying their frequency transforms. This is one of the many properties of the Fourier Transform.

Properties of Fourier Transform

Now, when you flip a signal X[n], you can also write it down as x[n1], where n1 = -n. If you look at the time scaling property, try replacing 'a' by -1. You'll observe that the F(W) will now become F(-W).

Since F(-W) is exactly the same as F(W), your result does not change.


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