[time-nuts] Question about noisetypes and ADEV

Ole Petter Ronningen opronningen at gmail.com
Fri Oct 26 05:34:41 EDT 2018


Hi, all

I'm simulating some noise to try to improve my somewhat sketchy
understanding of what goes on with the various noise types as shown on an
ADEV plot. Nothing fancy, ~3600 points of gaussian random numbers between 0
and 1 in excel, imported into Timelab as phase data, scaled to ns.

I mostly get what I expect; "pure" random noise, gives the expected slope
for W/F PM, -1. Integrating the same random data gives the expected slope
for W FM -1/2. Integrating the same random data yet again gives a slope
of +1/2, again as expected for RW FM.

However, looking at the data, I am somewhat baffled by a difference in the
starting point of the slopes. Given that this is exactly the same random
sequence, I would expect the curves to have the same startingpoint at
tau0.. Clearly not (see attached), but I do not understand why. Any clues?

Is this some elemental effect of integration (sqrt(n) or some such), or am
I seeing the effects of bandwidth and/or bias-functions or other esoterica?

In case the screenshot does not make it though;
W PM starts at 1.69e-9
W FM starts at 9.74e-10
RW FM starts at 6.92e-10

Thanks for any help!
Ole
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