[casper] Split pipelined/direct FFT math

[Stevo Bailey]

Hi CASPERians,

I'm working on a digital ASIC spectrometer like the Splash 
<https://casper.berkeley.edu/wiki/PIDDP_Spectrometer> one, but 
constructed in Chisel <https://chisel.eecs.berkeley.edu/> instead of the 
CASPER tools. Thus I'm implementing a number of DSP algorithms from 
scratch. I'm trying to work out the math behind a large-point FFT block. 
From my understanding, it consists of a number of biplex pipelined FFTs 
in parallel, followed by some reordering or phase shifting (is this 
necessary?), then followed by an in-place FFT. I have the biplex FFTs 
done. I'm looking for documents or publications discussing the math 
behind combining the parallel FFT results for the in-place FFT. Aaron 
has a paper 
<http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4840623> on 
this, but I was hoping for one with more detail.

Thanks!
Stevo