Practical Sscalable FFT question

Hello,

I am in academia so my knowledge on FFT are limited to what I find in
basic DSP books. I have a question on scalable FFT. This is mainly regarded
to OFDMA where they supports different bin numbers, ranging from 128 to
2048.

Now my question is how this is implemented in a FFT hardware module. I
think different methods must be using by different manufactureres. But I am
interested in a standard/general approach.

For example, if I want to do a 4-point FFT on a 8-point FFT module, is the
output taken from the first stage, instead of the 2nd stage for the 8-point
case? I am considering a raidx-2 butterfly structure. The case is more
complicated when you have to support from 128~2048 range.

Specifically, I would like to know:

1) Are the twiddle factors changed dynamically to the required FFT
points?
2) If so are they usually stored in some memory and read in?
3) OR am I getting the whole scalable FFT thing wrongly?

Thank you.

Sorry for bumping..anybody?

On Feb 22, 11:00&#4294967295;pm, "m26k9" <maduranga.liyan...@gmail.com> wrote:
> Sorry for bumping..anybody?

well, if i could more clearly understand what you're question is
about, i might try to answer.

r b-j