Dear Tim, You are aware that the CASPER FFTs are streaming, right? By this, I mean that they can accept data input at the full clock rate with no pausing between FFT windows. Everything Dan says is correct about latency, but historically there have been very few applications that have strict limits on absolute latency. I'm confused by the statement in your first email regarding not missing data. As long as the data lines all feed in to CASPER FFT inputs, no data are missed.
Aaron On Fri, May 2, 2014 at 10:12 AM, Dan Werthimer <[email protected]>wrote: > > tim, > > one more thought: > > the PFB FIR in front of the FFT dominates the latency of the PFB/FFT. > > the PFB has latency of (Ntaps-1) x FFTlength / Nparallelinputs. > > a four tap PFB has about three times the latency of the FFT, > so if you remove the PFB you will cut latency down by about a factor of > three > (assuming you remove the corner turn in the FFT). > > you can also put more inputs in parallel, as i mentioned in my previous > email, to cut latency down by factors of 2, 4, 8,... > > best wishes, > > dan > > -- Aaron Parsons 510-306-4322 Hearst Field Annex B54, UCB
