[time-nuts] AD9913 programmable modulus DDS. was: Re: An (unknown?) nasty feature of the DDS principle for time nuts applications

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Jan 25 14:53:53 EST 2011


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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