[time-nuts] Re: Simple simulation model for an OCXO?

[Magnus Danielson]

Hi Matthias,

On 2022-05-14 12:30, Matthias Welwarsky wrote:
> On Samstag, 14. Mai 2022 18:43:13 CEST Carsten Andrich wrote:
>> However, even for the 2^16 samples used by the CCRMA snippet, the filter
>> slope rolls off too quickly. I've attached its frequency response. It
>> exhibits a little wobbly 1/f power slope over 3 orders of magnitude, but
>> it's essentially flat over the remaining two orders of mag. The used IIR
>> filter is too short to affect the lower frequencies.
> Ah. That explains why the ADEV "degrades" for longer tau. It bends "down". For
> very low frequencies, i.e. long tau in ADEV terms, the filter is invisible,
> i.e. it passes on white noise. That makes it indeed unusable, for my purposes.

I agree. Good that we come to the same conclusion.

I just have not had time to run simulation and check, and I would check 
both spectrum and ADEV, but there is other tests to do such as 
autocorrelation function. A more unusual one is the increase of 
deviation of an ensamble of simlations, and thus the spread it can take. 
It depends clearly on the noise-type and length of sequence.

Cheers,
Magnus