Why do I see a reduction in the Dynamic Range, around the edges of my Radix-4 Burst FFT?
This is due to a problem in the way the core was implemented, in order to reduce the bit growth. Due to truncation at the output of the Butterflies, for the Radix-4 Burst, it causes the loss of dynamic range on the edges of the FFT results. This can be seen when applying a slot noise test to the FFT, as described in the data sheet.
This issue is being addressed in the next release of the FFT, v5.0, currently scheduled to be released in the Fall 2007.