[time-nuts] spur prediction DDS software

Brian Davis brimdavis at aol.com
Fri Jan 28 00:16:56 UTC 2011

Luis Cupido wrote:
>Is there a DDS spur prediction software around ?
>I mean for an arbitrary DDS design, like I would
>implement with logic or fpga etc.
 That <dds_oddities.pdf> file I linked to yesterday has a
couple references on page 4:

- Martin Pechanec’s MATLAB scripts ( mentioned earlier by Jim L. ),

- Zs. Pápay’s website and Mathcad files:

  I'd second Jim's suggestion of trying the Matlab scripts in Octave,
I'd guess that  the numerical sections would port easily but the
GUI stuff might need some rework.

  There's also a Mathcad-like free program called SMath Studio
( which I haven't actually used yet ) that might prove useful to try
setting up a model similar to those done in Mathcad.

  Note that the close-in phase truncation stuff discussed earlier
has a very long repetition period, so for big phase accumulators
you need either a huge FFT time record to see the phase truncation
rollovers, or else use a shorter FFT record and preset the phase
accumulator to a value shortly before the rollover.


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