Dan, This sounds to me like the behavior I see with long transforms with the maximum coefficient depth setting, where the block tries to use the trick of storing only rounded roots of unity for the last stages. I can't look into it in detail right now, but I recommend looking under the masks to find that parameter and setting it so that the value is greater than the number of stages in the transform to see if that fixes it. Glenn
On Thu, Aug 27, 2009 at 5:16 PM, Dan Werthimer <[email protected]>wrote: > > > dear casper collaborators, > > can anybody please advise ron on his question > appended below about problems with 32K point > wideband real transforms?? > > ron - does your 32K wideband real FFT work > correctly in simulation? > we've build instruments doing 32K complex transforms, > but these FFT's are complex (not real), > and they are biplex (not wideband), so this is > probably not a very useful data point. > > best wishes, > > dan > > > > [email protected] wrote: > ... > >> We have problems taking the Real Sampled Wide-band FFT >> (fft_wideband_real) from 16kpt to 32kpt. It works fine at 16k with 8bit and >> 10bit sampled data input and we have adequate chip resources and we don't >> believe it is timing issue. >> At 32kpt we have considerable unwanted spectra. Has anyone used this with >> SP block with this number of complex channels? We suspect a fault with SP >> block? >> >> Ron Beresford >> /Systems Engineer ASKAP/SKA / >> /CSIRO Australia Telescope National Facility/ >> /Vimiera & Pembroke Rds/ >> /Marsfield NSW Australia 2122/ >> /Ph 61-2-9372-4315/ >> /Fx 61-2-9372-4310/ >> /Mob 0428 294 711/ >> www.atnf.csiro.au <http://www.atnf.csiro.au/> >> >> This email is Australian made of entirely 100% recycled words. >> >> Please dispose of it thoughtfully. >> >> >> > >
