DDS Spur-Reduction Patent

Joe Gwinn · 2014-12-14T19:00:02+00:00

Back in mid 2009, I was researching how to get rid of the DDS spurs and phase bumps discussed in the recent "DDS Wisdom" thread. I found many approaches, mostly applicable or implementable only by the chip manufacturer, but I did find one approach that can be implemented using commodity DDS chips covered by a now-expired US patent, 5,598,440 to Domagala, titled "DDS driven DDS synthesizer for generating sinewave waveforms with reduced spurious signal levels". This patent also has a nice description of the causes of spurs. Also be sure to look at the patents that reference this patent. These patents will point out the problems with the present patent, and propose solutions. All in all, a good source of ideas. Be aware that this dual-DDS approach will not solve spurs due to truncation in the lookup tables. However, these kinds of spurs tend to be harmonic, so there can be a large reduction in close-in spurs. Joe Gwinn