Polyphase filter bank channelizer FFT or IFFT
Sorry, I didn't read the paper so this is just a guess.
FFT and IFFT are almost identical algorithms so it really makes no sense to code up both in an FPGA. Just use
$$F^{-1} (x) = F(x')/N, \\ F(x) = N \cdot F^{-1}(x)'$$
where N is the length of the FFT and &quot;'&quot; to conjugate complex operator.