@Dan: We apply sync pulse only once. From the memo you have mentioned, this is an acceptable mode. We do not apply resync pulses, and can also confirm that there is just one sync pulse.
@Dave: We have never seen such behavior in simulations. I am double checking though. @Ryan: Your observations are correct, but I do not understand what you mean by hooking up all outputs correctly. That seems to be fine. We are using the block's outputs correctly. FWIW, we run the design on two different FPGA clocks (150 MHz and 200 MHz) and see similar behavior. Thanks, Nimish On Fri, Mar 15, 2013 at 2:14 PM, Ryan Monroe <[email protected]>wrote: > Comments: > > -The FFT is probably fine. If it was broken, it would probably be 100% > broken. At least this looks like a spectrum > -It appears to me as if the broken section is exactly 1/8th of the > spectrum. Did you hook up all of your outputs correctly? > -What's up with the spikes in the spectrum? If they were interleave > artifacts, I'd expect to see the one which is at channel ~1800 closer to > 2048. Maybe they are some other tone though > > > > On 03/15/2013 12:14 PM, Nimish Sane wrote: > > Hi all: > > I am attaching a plot for Power of two inputs vs frequency channels. As > can be seen, we have this persistent problem where some channels at the end > just do not make any sense. We suspect that there is something going wrong > in the FFT block. Has anybody seen such behavior before or can think of > what may be going wrong? > > Following are some specifications that may be useful: > Hardware: ROACH2 with KATADC. > ADC Clock: 800 MHz, > FPGA clock: 200 MHz > Toolflow: XSG 11.5 with Matlab 2009b with RHEL5.8 > Libraries: SKA > FFT green block: fft_wideband_real > FFT size: 2^13 (4096 Output channels) > > Thanks, > > Nimish > -- > Nimish Sane > > Center for Solar-Terrestrial Research > New Jersey Institute of Technology > University Heights > > Newark, NJ 07102-1982 USA > > Tel: (973) 642 4958 > > Fax: (973) 596 3617 > [email protected] > > >
