[time-nuts] DDS'ery

John Miles jmiles at pop.net
Tue Jun 21 10:10:40 UTC 2011


> > to provide SFDR up to 150 dB (and I'd notice it if I were
> > getting much less than that in practice.)
> 
> has pushed me up! When I tell the compiler to generate me a 150 dB SFDR
> DDS
> then it produces an block with 28 (!) bits output witdh for the DAC. So, I
> am asking myself what wonder-chips you may be using as DAC for your DDS
> that
> features a dynamic range high enough to really measure a 150 dB SFDR?

It's being used as part of a digital downconverter in my case, not driving a
DAC.  In this application, DDS artifacts would ultimately show up as spurs
on phase noise plots or as ripple in ADEV plots.   I haven't seen any
unaccounted-for spurs above -130 to -140 dBc (where they could be coming
from pretty much anywhere), so I've been happy with the core's real-world
performance. 

-- john, KE5FX




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