04-11-2011 10:57 AM
Is the FFT Core (7.1) capable of accepting bit-reversed inputs and outputing the data in natural order? Specifically, I have a signal that I want to process using a forward FFT core configured to output the result in bit-reversed order. I then want to take the resulting data into an inverse FFT core, also configured to output the data in bit-reversed order, resulting in its output data being in natural order. I am able to successfully simulate with both cores configured for natural order inputs/outputs, but to save on resoursces/latency, I would like to configure the forward and inverse FFT cores to use bit-reversed outputs.
04-14-2011 07:53 AM
Any insight on this question would be much appreciated, even if the answer is no. I'm led to believe the FFT core is not compatible with bit-reversed inputs, but would like confirmation from those more experienced in the matter since I am relatively new to using this core.
08-31-2011 07:28 AM - edited 08-31-2011 07:29 AM
Actually I'm interested in this topic too.
An option for bit-reversed inputs would be especially useful for doing fast convolution using overlap-discard and overlap-add methods. Since this is basically a FFT followed by an IFFT, it would be very resource efficient if both cores could work with bit-reversed outputs and inputs respectively.
Unfortunately this is not possible since the FFT/IFFT cores support only bit reversed outputs, and I don't see an easy way of getting a bit-reversed input IFFT from a bit-reversed output IFFT.
I wonder how am I supposed to implement fast convolution using coregen-FFTs. The only options I can think of is using the BRAM-expensive natural order FFT and IFFT.
08-31-2011 09:42 AM - edited 08-31-2011 09:43 AM
bpelger is correct, Bit reverse input is not supported at this time.
Natural order FFT/IFFT will allow implementation of fast convolution algorithms.
08-31-2011 04:07 PM
Could you please open a webcase requesting FFT core supporting inputs in bit-reversed order? If yes, please send me the webcase number via PM.
I just had the impression that fast convolution is such a standard task, that I must be missing an option or something else in coregen. Thanks for the clarification.
03-15-2012 11:15 AM
I am very interested in FFT core with bit reversal output and input back into IFFT (with the same bit reversal order) and get natural order out.
03-15-2012 11:20 AM - edited 03-15-2012 11:20 AM
Yes, a case was opened for this. The possibility for bit reversed input is being investigated. No firm plans at this point, though.
I recommend you contact your FAE and provide feedback to them so they can communicate with marketing.