Re: windowing and zero-padding

On Mar 7, 11:16 am, M.Aram...@xxxxxxxxxxx wrote:
Suppose I have a sequence of n samples where n is not a power of 2 and
I zero-pad that
sequence up to the next power of 2 number of samples before computing
the FFT of the
resulting padded sequence.

If I want to apply windowing (e.g. Hamming) before computing the FFT,
should the window
width used to compute the windowing weights be n (the original number
of samples) or
should it be the next power of 2 (i.e. padded) number of samples?

-Michael

Michael,

The window should be the same length as the data, not rounded up to
the next power of 2.

Also, you want to use the definition of the window where the 1st and
last point are the same. For 'n' data points, and an 'n' point FFT,
the 2nd point and the last point are usually the same. The first
window is symmetric, the second is implied symmetric when you consider
the implied periodicity of the data being FFT'ed.

Dirk
.

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