Re: FFT Length
Hello!
Just in case, here is a simulation program (not published yet) that gives a good
idea of what FFT does.
The input is a sine wave and its frequency can vary between 0 and 0.5 fs.
The number of points can be changed in realtime.
There is also a possibility of changing the input windowing and the results of the
windowing appears immediately in the input window. The window can be chosen
among rectangle, Bartlett, Hann, Hamming and Blackmann.
At one point, I have entered 0.25 manually as the input frequency. In this case,
as it is a submultiple of the sampling frequency, the coefficient cancel each other
nicely and the result peak is extremely acute.
Note that the resolution (variable from 256 to 4096) has a great influence on the
peak shape. At 4096, it becomes very acute, close to the ideal Dirac pulse in any
case.
NB: since the spectrum is symmetric, the program displays only half of it.
Dora