[time-nuts] DDS in GPSDO design?

Bob Camp lists at rtty.us
Tue May 29 00:12:05 UTC 2012


Hi

Not sure if you could do it with just a straight PRNG or not. The idea is normally approached as picking the codes you hop between so the errors (phase and amplitude null out. In practice that may not be any different than random since you don't really know what the D/A is doing.

Bob

On May 28, 2012, at 11:15 AM, Poul-Henning Kamp wrote:

> In message <D0519DF5-E693-45CE-8A6F-C8CF35DDE61C at rtty.us>, Bob Camp writes:
> 
>> The 9852 can be dithered from an external source. Of course, to
>> be effective, you need a source that can calculate and transmit a
>> multi megabit / second bit stream to do it. That gets you right
>> back to the FPGA.
> 
> There are dedicated PRNG chips which would do a pretty good job,
> as would pretty much any streaming crypto chip in feedback mode.
> 
> It's probably not cheaper than the FPGA, but you would avoid
> the VHDL issue.
> 
> I like Rich's mixing synthesizer much better.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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