[Scilab-users] Padding and clipping a grid

[Samuel Gougeon]

Hello Lester,

Le 29/07/2018 à 13:18, arctica1963 a écrit :
> Hello all,
>
> I need to increase the dimensions over which the FFT is calculated to avoid
> edge effects,

AFAIK, padding the initial signal does not avoid edge effects (i guess 
one deal with edges discontinuity).
It can even be the source of discontinuity, and so yield fake high fft 
amplitudes at high frequencies.
It will be the case if  the original signal S has no edge discontinuity 
( S(1)~S($)) but you padd
it with zeros while its edge does not fall to zeros (=> |S($)|>>0, 
S($+1)==0). Even worse,
in this case, windowing the signal will no longer be effective, since 
the padding will move
the discontinuity in the body of the padded signal instead of on 
signal's edge.

Padding a signal increases the lowest frequency of its numerical FT, 
that is the sampling frequency
of its FFT. AFAIUnderstand, there is no edge matter there.

But this is more a signal processing topic than a Scilab one.

Regards
Samuel