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Beyond the first Nyquist zone

Question asked by Engr.for.Radio.Astronomy on May 15, 2012
Latest reply on May 15, 2012 by Engr.for.Radio.Astronomy

All AD DDS chips recommend operating the DDS chips in the first Nyquist zone (up to 0.4 times the clock frequency). However, in some cases (for example figure 27 of the AD9852 datasheet) show DDS output frequencies falling in the third Nyquist zone. There is not much other discussion about operation in these other Nyquist zones.

 

This causes confusion among my managers and colleagues. They point to the first Nyquist zone recommendations and say I have to operate there. I say I can operate in any Nyquist zone I choose as long as I am cognizant of clock harmonics and aliases.

 

Once and for all, can you explain any and all other pitfalls associated with DDS operation in the higher Nyquist zones and the ultimate Nyquist zone limits (besides power level), if there is one? (Currently, I am evaluating an AD9858 in the second Nyquist zone it it appears for my purposes it is very clean.)

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