[time-nuts] An (unknown?) nasty feature of the DDS principle for time nuts applications

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Jan 25 23:55:49 UTC 2011

Another description of such artifacts occurs in the tutorial:


Gerhard Hoffmann wrote:
> Am 25.01.2011 15:35, schrieb Ulrich Bangert:
>> see page 8.6ff of the service manual to see that the HP3325 is not 
>> DDS based
>> but uses a "Fractional N Synthesizer scheme" which is something 
>> completely
>> different and is not prone to the described effects.
> Yes, it's f-N, I must have stored that in the wrong winding of my 
> brain...
> Fortunately, I had no need to repair my 3325B upto now.
> BTW, your effect has been described in detail in the article that
> Bruce cited on jan7 in the NoStateOfTheArtCounter thread.
> <http://sdrforum.org/pages/sdr06/sdr06_papers/1.3/1.3-01.pdf >
> (seems not to work anymore, may be a typo of mine)
They've changed their name to

However finding that paper may take a while.
> In the meantime, I have published my sin/cos table on
> http://opencores.org/project,sincos
> It should be easy to generate a version with BCD-coded phase input
> to make a decimal-friendly DDS.

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