Efficient Calculation of Complex Analytic IFFT

Hi All,

My question is as follows. When calculating an N-point IFFT with the
inputs conjugate symmetric (real output), this can be performed using a
single N/2-point IFFT and some pre and post processing.

Is there any method to do this (use a single N/2-point IFFT) with half the
inputs set to zero instead of the complex conjugate? (and thus getting the
complex analytic output instead of the real output?)

Thanks, Nadav



		
This message was sent using the Comp.DSP web interface on
www.DSPRelated.com

nadavf wrote:
  > Is there any method to do this (use a single N/2-point IFFT) with 
half the
> inputs set to zero instead of the complex conjugate? (and thus getting the
> complex analytic output instead of the real output?)
> 
> Thanks, Nadav

I won't call it impossible ... but I doubt it.

Look at the inverse operation that would be possible if that were true.

It would be equivalent to zero-padding a length N sequence to size 2N 
and doing a 2N fft on it for the cost of a 1N fft.  In other words, 
you'd get the increased/interpolated frequency resolution for free.


-- Mark