[time-nuts] DDS module

Bob Camp lists at rtty.us
Sun Jul 21 12:39:32 EDT 2013


Hi

How big and where are things that you need to know a bit about the DAC's "issues" to be completely sure of. You can be sure that they are well above of the phase noise floor of an OCXO and that they are spaced less than the distance to the frequency of the nearest "good" word. Since it's a square (dac issues) / sawtooth (truncation stuff) wave sort of thing, you will have *lots* of them...

Bob

On Jul 21, 2013, at 12:10 PM, Hal Murray <hmurray at megapathdsl.net> wrote:

> 
> lists at rtty.us said:
>> If the DDS is acting pretty much as a divider you don't get a lot of spurs.
>> The rest of the time there are spurs *somewhere* in the output spectrum. Put
>> another way, there are thousands of "bad" tuning words for every good one.
>> The good ones are evenly spaced over the range at a spacing determined by
>> the DAC width and the phase truncation process.  
> 
> Look at the DDS word in binary.  Bits farther to the right turn into spurs 
> closer in.
> 
> The other question is how big are they.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.



More information about the time-nuts mailing list