Hi By far the best approach is to use actual data. Grab a pair of OCXO’s and compare them. A single mixer setup is one easy ( = cheap ) way to do it. You will get the sum of the two devices, but for simulation purposes, it will be *much* closer to reality than anything you can brew up with a formula.
Bob > On May 2, 2022, at 10:12 AM, Matthias Welwarsky <time-n...@welwarsky.de> > wrote: > > Dear all, > > I'm trying to come up with a reasonably simple model for an OCXO that I can > parametrize to experiment with a GPSDO simulator. For now I have the > following > matlab function that "somewhat" does what I think is reasonable, but I would > like a reality check. > > This is the matlab code: > > function [phase] = synth_osc(samples,da,wn,fn) > # aging > phase = (((1:samples)/86400).^2)*da; > # white noise > phase += (rand(1,samples)-0.5)*wn; > # flicker noise > phase += cumsum(rand(1,samples)-0.5)*fn; > end > > There are three components in the model, aging, white noise and flicker > noise, > with everything expressed in fractions of seconds. > > The first term basically creates a base vector that has a quadratic aging > function. It can be parametrized e.g. from an OCXO datasheet, daily aging > given in s/s per day. > > The second term models white noise. It's just a random number scaled to the > desired 1-second uncertainty. > > The third term is supposed to model flicker noise. It's basically a random > walk scaled to the desired magnitude. > > As an example, the following function call would create a phase vector for a > 10MHz oscillator with one day worth of samples, with an aging of about 5 > Millihertz per day, 10ps/s white noise and 10ns/s of flicker noise: > > phase = osc_synth(86400, -44e-6, 10e-12, 10e-9); > > What I'd like to know - is that a "reasonable" model or is it just too far > off > of reality to be useful? What could be changed or improved? > > Best regards, > Matthias > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.