Folks, Please be careful about definitions in this discussion.
To some people, "phase noise" refers to sideband noise, away from the carrier, arising from some form of random phase modulation of the carrier. To others, the same term refers to the underlying phase modulation itself. While intimately related, the two meanings refer to different manifestations of the same root cause, and casual (unqualified) use of the term "phase noise" can lead to considerable confusion. Thanks, Dana On Fri, Mar 15, 2019 at 12:01 PM Attila Kinali <att...@kinali.ch> wrote: > > Did someone say "noise processes"? :-) > > On Fri, 15 Mar 2019 10:03:11 -0400 > John Ackermann N8UR <j...@febo.com> wrote: > > > For a presentation on basic time-nuttery, I'd like to find > > non-oscillator examples of the various noise processes -- white PM, > > flicker PM, white FM, flicker FM, random walk. (I'm not sure if FM and > > PM have any relevance outside oscillators, though.) > > First you have to define what you mean by FM outside of oscillators. > If you look at frequency just as integral of phase, then there is > a very straight forward relation. Ie frequency noises are just > phase noises with the exponent going up by two. > > white noise (~white phase): > The most important white noise source is thermal noise, ie movement > of atoms that disturb(scatter) the flow of electrons due to thermal energy. > The second most important noise is shot noise in semiconductors. > This is mediated by the fact that the current carriers (e.g. electrons) > are discrete objects that pass through a potential barrier. > There is also avalanche noise which is present in p-n junctions with > high electric fields where electrons are accelerated to the point where > they gather enough energy to knock out secondary electrons from atoms > in the lattice before leaving the active zone. Avalanche photo diodes > and zener diodes with voltages over 6V are the most common devices that > exhibit > predominantly avalanche noise. > > 1/f noise (~flicker phase): > This noise comes mainly from defects in conductors or other structures > that trapp or scatter the electrons (or phonons in crystal resonators). > This type of noise is very common and can be found in almost all physical > systems (even weather patterns), but it's exact source is not well > understood. > > 1/f^2 noise (~white frequency): > There are two types of noise here: > 1) Popcorn noise: Like 1/f noise, this is not well understood, but > is also related to the activity of single traps in regions of high > current density. It was more a problem back in the vacuum tube and > germanium semiconductor times. Current silicon semiconductors show, > if any, only very low levels of popcorn noise. > 2) generation-recombination noise: when electron-hole pairs form or > get recombine, the carrier density changes localy. Above the frequency > that is inversly proportional to the recombination time, this type > of noise shows a 1/f^2 characteristic (below it's white) > Additionally to those two real noise sources, you also have the > integration of white noise. This can either happen due to a real > integrator or by a device that has integrative properties within > the circuit (e.g. the Q of the resonator in Leeson's formula) > > higher order noises (~flicker frequency and above): > From what I've read in the last years, I have formed the hypothesis > that most (all?) noises with higher exponents are formed either due > to integration of the above noise sources[1] or are mediated > through environmental effects that make it look like noise sources[2] > when analysing them with our tools, but in reality are not truly > random and/or not Gauss distributed. E.g. in Enrico's paper[3] > you can see that thermal effects lead to a 1/f^5 type noise. > I still need to figure out a way to prove/disprove this hypothesis > and I do not think this way of thinking is generally accepted (I have > not seen anyone else formulating this), so please take this with a > grain of salt. > > HTH > > Attila Kinali > > > [1] Eg. Leesons formula for oscillators. Similarly, passive frequency > standards which do a frequency detection that exhibits white and 1/f noise, > which thus turns the output noise in into white frequency noise and > flicker frequency noise. > > [2] I use here a somewhat more strict definiton of noise surces. > Namely sources which generate random, Gauss distributed values > with an 1/f^a, a >= 0 power spectral density. While for practical > purposes using this strict definition does not make sense (if it > looks like noise, then it is noise), but from a theoretical point > of view it is important to distinguish other effects that can be > explained and thus potentially removed (e.g. by measuring temperature > of the device itself very accurately) from "real" noise sources. > > [3] "Low Flicker-Noise DC Amplifier for 50Ω Sources", by Enrico Rubiola > and Franck Lardet-Vieurdrin, 2004 > > http://rubiola.org/pdf-articles/journal/2004rsi(rubiola)low-flicker-dc-amplifier.pdf > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neal Stephenson > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
