FFT in blocks

Al wrote:


> wow, thanks for your reply, I'll have a look at it.
> Now I'm not taking care about the phase so I could discard those phase
> rotations I think. Since now I was just performing 8 FFTs of 64 blocks
> of consecutive data (not mixed as you said) and summing up them all,
> but probably that's not correct
> 
Nope, the phase rotations are required as part of the FFT computation, 
they are done between the smaller FFTs.  That mixed radix algorithm is 
simply a decomposition of the Fourier transform to allow you to compute 
a larger FFT using smaller kernels.  You need to do this in order to get 
the spectra of a 512 point FFT.  If you skip the phase rotations, you 
are basically doing a 2D FFT on data in an 8x64 array.