Fast Fourier Transform
 

Dear Madam/Sir,
I have a simple question about the use of the Fast Fourier Transform option
in the Data Analysis package.
1. After the transform of a row/column a row/column of the same length is
obtained with complex numbers.
2. The (time) step between two input data is denoted by dT.
3. First question: Let the output be Xn = An + i.Bn. What is the exponential
function: Exp{i.n.t/dT} or Exp{i.p.n.t/dT} or Exp{i.2p.n.t/dT} ?
(in which t = time )
I couldnt find the correct answer in the Office help and I know there are
differences between FFT packages.
4. Lets assume the third expression is correct; than the real part of the
expression will be: Real[Xn.exp{i.2p.n.t/dT}] = An.Cos(n.w1.t) -
Bn.Sin(n.w1.t)
Is this correct ?
5. Are there already tools available in which the limitation for N=2^k is
not needed.

If you can help me with these questions it would be a great help for me.
Thanks in advance and best regards
Ad Pronk
Ministry of Transport, Public Works and Water management
The Netherlands
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