[time-nuts] Measuring ADEV using TBolt-Tic tester
azelio.boriani at screen.it
Thu Oct 13 17:31:09 EDT 2011
Oh, yes, you're right. 100pS is the noise. Very interesting in this case:
how this high resolution is obtained (excluding averaging, the real hardware
resolution)? Analog interpolators? Wave union TDC? Vernier delay lines? I
haven't found any reference in the internet...
On Thu, Oct 13, 2011 at 11:10 PM, ws at Yahoo <warrensjmail-one at yahoo.com>wrote:
> You missed something somewhere
> The Tbolt's RMS noise is 100 ps for the phase and 10 ps noise on the PPT
> using unfiltered one second data.
> These include the RMS sum of several noise sources.
> The resolution is sub ps.
> The noise is much greater than the resolution so averageing works fine
> Azelio Boriani azelio.boriani at screen.it
> OK, so the Tbolt hardware resolution is 100pS. If you have a hardware
> resolution of 100pS and do an average over the data, yes, you can obtain
> greater resolution but your data has to cross the 100pS boundary to have
> variation. If your phase moves under the 100pS window your averaging can
> only say that the phase has not crossed the 100pS boundary by an arbitrary
> lower resolution obtained with averaging. Of course all must be stable.
> Maybe the trick is to use a sampling oscillator that is not so stable so
> that it can move the 100pS window to reveal if the phase is near one edge
> the other and "feed the average" with numbers that are not all the same.
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