FFT Question

[James Goodley]

I am using complex FFT and complex IFFT. Does anyone know
what the exact scaling is? ie I think they do not have a divide
by N (samples) within them. I initially need periodogram from a time
series
and so am taking the FFT (can be real) and doing a

magnitude squared (complex)/(2N) on the output. Does this look right
What about the inverse complex FFT?

James

[AA Dan]

James,
The Complex FFT.vi and Inverse Complex FFT.vi do not have a divide by N samples built in. You can take an array size to get N - number of samples.

As for the rest of your question, could you please provide me with more detail about what you are trying to do? I am not sure, but I believe that if you are trying to obtain the Amplitude of your sample by performing a magnitude squared operation, you might be able to use the built in functionality of the "Amplitude and Phase Spectrum.vi" to find the Amp Spectrum Mag (Vrms) which is the single-sided, amplitude spectrum magnitude. You can look at the detailed help on this function by right clicking on it in the block diagram and going to "help".

If that is not what you are looking for, could you please give me
more information about what you are trying to do? Thanks and have a great day.
-Dan Hoar
Applications Engineering
National Instruments