Warren,
On 10/23/2012 12:45 AM, WarrenS wrote:
Tom said:
In general, when you discipline a OCXO you get that characteristic ADEV
"hump".
At some point there is a cross-over and you know/assume that at that
point
each must be contributing 1/sqrt(2) of the noise.
Although putting the Hump at the cross over point is typically a good
compromise, there are other choices which give different trade-offs.
Attached is a excell plot showing the effect of different PID tunings
on the Hump's size and location.
This spread sheet (originally is from Wenzel's site) was for plotting the
effect of the RC H/W values for a PLL when used as a clean up Osc,
but can be used for setting the PID values of a disciplined GPS
such as a Tbolt with a few changes and using different data.
As expected, the hömp (sorry for sudden Inspector Clouseau) depends
greatly on the damping factor. Lowest hump you get from the high
damping-factor (40) located at the cross-over point of the two curves.
The remaining hump is what you need to live with as the noises is
spliced together by the high-pass/low-pass action of the PLL.
Good illustration. I haven't seen it before, but it is expected.
Cheers,
Magnus
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