Will this be able to discipline a rubidium oscillator as well as a OCXO?
Maybe you could switch in a divider network to close in the trim range as
the oscillator precision improves.
Hope someone makes a PC board available. Count me in for some.
----- Original Message -----
From: "Azelio Boriani" <azelio.bori...@screen.it>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Friday, September 14, 2012 3:33 PM
Subject: Re: [time-nuts] GPSDO control loops and correcting
quantizationerror
Also you need a super ultra fantastic voltage reference for a 32bit DAC.
Anyway, yes, in my GPSDO the controller has 3 levels: at startup is fast,
then slow and then very slow. The levels trigger when the precision
estimate is 10E-9 and 10E-11. If you have a resolution of 10nS then take 10
averages and your resolution will be 1nS and so on. When I switch level,
the number of averages is increased too but this leads to a slower DAC
update rate. This is the problem: now I'm trying to figure out if the
corrective action can be "predicted" (Kalman filtering) and applied at the
same speed.
On Fri, Sep 14, 2012 at 8:52 PM, Chris Albertson
<albertson.ch...@gmail.com>wrote:
On Fri, Sep 14, 2012 at 11:21 AM, Michael Tharp
<g...@partiallystapled.com> wrote:
> Finally, do people think a 16 bit DAC is adequate or should I consider
> building a 32-bit one? I looked at a few designs when putting this
together
> but decided to keep it simple until things were up and running.
Having a 32-bit DAC would give you enough range so that you could drop
in any OCXO you might have. But if you can have trimmer resisters to
selected for your specif OCXO then 16-bits should be enough. If it
were me, I'd want the DAC steps to be smaller than what the phase
detector can measure. Said another way a 32-bit DAC might
eliminate the need for scale and offset trimmer resistors.
Chris Albertson
Redondo Beach, California
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