On 11/28/2013 08:18 PM, Attila Kinali wrote: > On Thu, 28 Nov 2013 10:35:33 +0100 > Wolfgang Wallner <[email protected]> wrote: > >> I'm interested in the simulation of oscillator noise (especially in discrete >> event simulators). >> I came across this topic as part of the literature research for my master's >> thesis, and have to admit that I really underestimated how complex this >> topic is. > Hehe. Join the club. But treat carefully, this can become quite addictive ;-) > > Can you explain what you are exactly doing? You talk about noise, but > only mention allan deviation. ADEV is the right tool to measure stability, > but not so much phase noise. On the contrary, ADEV (and MDEV even more so) is designed to separate noise-types such that they can be estimated separately. It is only of lately that you can use both phase-noise plots and timer-based ADEV/MDEV plots to achieve the same thing, not that the phase-noise characteristics have been hard to estimate from, but rather that it has been hard to achieve qualitative measures for precision sources such that all noise-forms can be used for estimation. This have been easier in the TIC-driven measurement. > >> In the past weeks, I have spent a lot of time reading about different kinds >> of variances, and I think I have a basic understanding now. >> >> I would like to ask you two questions: >> >> 1) Do you have any advice for me on what papers to read concerning >> oscillator noise simulation? > What part of the oscillator? Noise of the feedback electronics? > Noise of the output stage? Noise from environmental factors? > Noise intrinsic to the quartz crystal resonator? > > How accurate do you want the model to be? > > How do you simulate the complete oscillator? > (this is a big topic of its own, and definitly not easy) > > Did you read Enrico Runbiolas Book "Phase Noise and Frequency Stability > in Oscillators"? If not, you should start with that. It gives a nice > overview of all the basics you need to understand this topic. Strongly recommended reading. His view is phase-noise driven.
I think one should study "both sides of the coin" since they have different benefits and different usages. > Gangepain did a lot of research on noise sources and stability of > quartz oscillators. You might want to look up papers from him. > (there was somewhere a collection of them) > > > A couple of weeks ago, i did a literature search on various stuff > around low noise/high stability oscillators. But i didn't have the > time to sort those papers yet, much less read them. But i can search > for things in there, if you tell me what you are looking for. > > >> I have read different kinds of papers up to now, but non of them was really >> what I was looking for: > What are you looking for? > > >> *) One of the papers I have read is "Accurate Clock Models for Simulating >> Wireless Sensor Networks" by Ferrari, Meier and Thiele. >> But I don't think their simple model is of any use, as they completely >> ignore the typical allan variance of oscillators. > Well, Thieles group does mostly wireless sensor networks (catually most > of the TIK institute does wireless sensor networks in one form or another). > Their use for an "accurate" clock is to minimize the on time of the RF > circuit in order to minimize power consumption. IIRC their goal was to > get down from synchronisation window of 1s to 0.1 on a time scale of > a couple of minutes to a couple of hours. And the whole calculation > had to be simple enough to be done on an 8bit ATMega while not > taking considerable computation time. > These requirements lead to a rather simple model of clock deviation. > >> *) On the other hand, the paper "Achieving a Realistic Notion of Time in >> Discrete Event Simulation" by Gaderer, Nagy, Loschmidt and Sauter describes >> a very realistic model, but they keep the implementation details to >> themselves. >> *) What could be of use for my purpose could be "Simulation of Oscillator >> Noise" by Barnes, but as it is from 1988 it is quite dated. > I dont know these two papers, but they dont look too bad. > > As for the age. Most of the theoretical work on quartz oscillators > was done in the 70s and 80s. Also most of the books on quartz > oscillators are from that time. There are very few books from the 90s > and later. If you want more modern papers on simulation of noise, then there is a few from JPL that applies, but the site where unfortunatly dropped in one of the server-roundups. >> 2) Do you know any public data samples of the allan variance of a real >> oscillators? > febo.com (John Ackermann) and leapsecond.com (Tom van Baak) have both some > data on various crystall oscillators. > >> When I look in the data sheets of oscillator that I find on the internet, >> they only have precision estimates like 1ppm or 1ppb, but no detailed allan >> variance graphs. > Yes. Because in the class of cheap AT cut oscillators, you dont worry about > allan variance. The instability due to temperature dependence of your > system is much higher than the temperature-free (in)stability. The ADEV > becomes "relevant" only after you do at least a temperature compensation > or temperature control. The specification for temperature variations is a poor excuse too. Some vendors have learned that the hard way. >> PS: When I use the word oscillator I mean the cheap quartz oscillators as >> found in typical consumer electronic stuff. >> PPS: I'm not sure if this mailing-list is the right place to ask my >> questions, as simulation is not listed in your mailing-list topics. >> Sorry if this mail is off-topic. > Don't worry, you are at the right place :-) I agree. :) Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
