God kväll Magnus, On Sun, 20 Mar 2016 20:43:00 +0100 Magnus Danielson <mag...@rubidium.dyndns.org> wrote:
> > If not, does someone have pointers how to write realistic oscillator models > > for this kind of short and long term simulation? > > It is a large field that you tries to cover. What you need to do is > actually find the model that models the behavior of your physical setup. Yes, there is quite a bit I need to cover. I started out to put some stuff together yesterday, but I guess it will take me two or three weeks until i have something half way usable. > You need to have white and flicker noises, there is a few ways to get > the flicker coloring. I did some hacking of the setup, and ran tests > against Chuck Greenhalls original BASIC code. I'm currently using the code from Brooker and Inggs[1,2], but the code is quite convoluted and it will take me some time to extract it and get it working properly. (but then, it's the only piece of code that I found that does seem to be viable at all) > You probably want a systematic effect model of phase, frequency and > drift. Also a cubic frequency vs. temperature. All the properties needs > to be different for each instance. Similarly, the flicker filter needs > to be independent for each oscillator. What do you mean with "the flicker filter needs to be independent"? Each oscillator will get its own noise source, if you mean that. > Similar enough things have been tried when simulating the jitter and > wander in the G.823-825 specs. Thanks, i will have a look at those. > An aspect you need to include is the filtering properties of the EFC > input, it acts like a low-pass filter, and the Q of the resonator is > another catch-point. The low pass filter is easy to implement, and yes, this will be one of the first things i need to implement. One of our guesses is, that this low pass filtering helps us getting the high performance we saw. I am not sure yet, how to model the Q, or whether that actually needs to be modelled with anything else but the proper noise/stability characteristics and the low pass on the EFC. > I wonder how complex model you need to build before you have catched the > characteristics you are after. The current plan is to implement an oscillator model that mimics the correct stability i'm seeing, then add EFC (first w/o low pass filtering). This should already work "properly" and give a first indication on how the system behaves. Then step by step add the non-idealities, like the low pass filter on the EFC, the high DNL of the TDC, the noise on the pulse output and the TDC input, ... until I get close to what we measure. > The EFC measures you have done so far indicate that your steering > essentially operates as if you do where doing something similar to > charge-pump operation. Hmm.. can you elaborate a bit on why you think so? Attila Kinali [1] "Efficient Generation of f^a Noise Sequences for Pulsed Radar Simulation", by Brooker, Inggs, 2010 http://dx.doi.org/10.1109/TAES.2010.5461653 [2] http://rrsg.ee.uct.ac.za/fers/ -- Reading can seriously damage your ignorance. -- unknown _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.