[time-nuts] General query about disciplining circuitry

[AC0XU (Jim)]

I can image all sorts of disciplining circuits for controlling a digitally-controlled oscillator against GPS. Presumably, I will measure oscillator phase at the 1 PPS times and run those values into a Kalman Filter. I think my question is about how best to measure the oscillator phase, given the constraint of low electrical power (<1W). There are zillions of commercial devices that do this but the mfrs generally do not advertize the details. I plan to use either an MCU or an FPGA, depending on which is more advantageous.

I looked at
<https://hackaday.io/project/6872-gps-disciplined-xcxo/details>https://hackaday.io/project/6872-gps-disciplined-xcxo/details 
and that seems interesting. I don't have to worry about VCO control because my oscillator has a digital control.

What about measuring the phase of a large divider PLL locked to the reference? With I-Q outputs the phase can be measured with a very slow ADC applied to a sample-and-hold triggered by the 1 PPS.

Thanks!
Jim