Hal Murray wrote: >> I don't understand this area well enough. Can somebody give me a few (more) >> hints? >> >> Are we talking analog filters in hardware or software filters in a small CPU? >> >> How narrow an analog filter can I purchase or make? (at reasonable price or >> board space or design time or whatever) >> >> How close do the spurs get? I thought they got quite close if the DDS >> parameters were close to a good frequency. Do they get smaller as they get >> closer, or something convenient like that? >> >> What's the term for the set of frequencies that a DDS can make with no >> spurs? >> Say with a divide by 8. I'm guessing that the criteria for that is >> something like >> no bits left on in the low bits when the carry out of the low bits happens. >> By low bits I mean the ones the A/D doesn't see. >> >> >> >> > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >
Hal Some references on DDS spur analysis http://tycho.usno.navy.mil/ptti/ptti2005/paper8.pdf http://www.highfrequencyelectronics.com/Archives/Oct06/HFE1006_Groulx.pdf http://marstech.jpl.nasa.gov/tdaPublications/AnAdvSynthesizedUltra-StableOscillatorforS-CApplic.pdf http://www.xilinx.com/bvdocs/ipcenter/data_sheet/dds_ds558.pdf Another technique for reducing spurs whilst raising the noise floor is to use to dither the DDS frequency tuning word. http://www.patentstorm.us/patents/6785345-description.html http://www.patentstorm.us/patents/5598440-description.html Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
