Since the 9913 lacks a means of low pass filtering the DAC reference it may well suffer from significant AM noise sidebands. With a well designed sine to square converter as required when using it as part of an offset source like that outlined in Rick's paper (probably desirable to reduce the phase noise floor of the offset source) this characteristic shouldn't be a significant issue.

Bruce


Richard (Rick) Karlquist wrote:
What you need is the AD9913.  It has a programmable modulus.
Now you're not stuck with 2^32.  You can pick any convenient
value.

Rick Karlquist N6RK

On 1/25/2011 5:37 AM, Ulrich Bangert wrote:
Gentlemen,

the pros and cons of DDS chips and how to improve them have been discussed
here from time to time. Most of the improvements have the aim to remove
spurs out of the power spectrum or to reduce the noise level. Yesterday I
run into a thing that may make it very qestionable whether DDS based
circuitry is in general good for precise timing applications.




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