[time-nuts] Re: What phase variations to expect in a DMTD due to temperature fluctuations?

[Tom Van Baak]

 > Are these levels to be expected?

I'd say 1 ps / C is fine, but the 10 ps number seems high so you may 
want to identify the source of that. For some context look at the specs 
of a metrology grade distribution amp:

https://spectradynamics.com/products/hpda-15rmi-high-performance-distribution-amplifier-1-50mhz/

Its tempco spec is 1.5 ps/C, which sounds good enough for a professional 
timing lab to me. Even if you had 3 C modulation of temperature that's 
under 5e-15 @1000 s so it would be in the noise. And if better 
performance was required you can simply keep the room to 0.3 C instead 
of 3 C. That way everything in your lab -- cables, connectors, power 
supplies, oscillator references, measurement instruments -- improves 
accordingly.

Another example is John Miles' TimePod [1] and PhaseStation [2]. Note 
these are not spec'd explicitly in ps/C but rather ps/hour. I had not 
seen that before.

/tvb

[1] https://www.miles.io/TimePod_5330A_user_manual.pdf

[2] 
http://ww1.microchip.com/downloads/en/AppNotes/AN3526-Dual-Reference-Noise-and-Stability-Measurements-with-the-53100A-PNA-DS00003526A.pdf


On 10/23/2022 9:05 AM, Erik Kaashoek via time-nuts wrote:
> During the testing of a DMTD there appears to be a "large" sensitivity 
> to temperature variations.
> Opening a door in the room with the DMTD causes changes in the phase 
> difference in the order of 1 ps
> Blowing cold air over the encased DMTD causes phase variations up to 
> 10 ps.
> The analog part of the DMTD exists out of some coax, SMA connectors, 
> active mixers and ADC's. The rest is digital and not expected to be 
> temperature sensitive.
> Its not clear yet which parts are causing the temperature sensitivity
> As the design is symmetric (both inputs have the same components 
> almost the same layout) I did not expect this.
> Are these levels to be expected?
> Erik.