# How do apply window in the Frequency Domain for a signal that was zero padded before FFT?

Started by February 10, 2014
```On Sun, 16 Feb 2014 02:45:52 -0800 (PST), martin.mullins942@gmail.com
wrote:

[Snipped by Lyons]

Sorry for not replying to you sooner.

>I'm zero padding from a 2^n to 2^n, say K=2048 window length and N = 8192 the fft length.
>
>After the suggestions from this article it works but only for the case
>of zero padding only after the original data rectangle window.
>ie. x(n) = [data (len: K)][zeros (len: N-K)]                  -- (1)
>If X(m) = FFT{x(n)}
>Then X_window(m) = alpha*X(m) - beta/2 * X(m-N/K) - beta/2 * X(m+N/K)
>So the only difference is that instead of X(m +/- 1) terms its X(m +/- N/K)
>(Was determined by taking the FFT of the hanning window).

You wrote:

"X_window(m) = alpha*X(m) - beta/2 * X(m-N/K) - beta/2 * X(m+N/K)"

I don't think that's correct, but I'll have to do some
software modeling to be sure.   Your original question is an
interesting question, and I intend to find the correct