Good evening! I'm going through some old stuff...
On Wed, 27 Nov 2019 00:29:19 +0100 Jan-Derk Bakker <jdbak...@gmail.com> wrote: > This has yielded a combined "simple" signal > processing path of a differentiator, a double comb filter and the offset > estimator, which is getting very close in performance to the "ideal" band > pass filter (OADEV of 3.77e-13@tau=1s versus 3.25e-13@tau=1s for the BPF; > full plot: > http://www.lartmaker.nl/time-nuts/DMTD%20self-noise%20OADEV%20with%20PLL%20and%20various%20filters.pdf > for this 600000-second recording: > http://www.lartmaker.nl/time-nuts/600ksec%20run%20with%20PLL,%2010811%20through%20splitter.png > . OADEV past ~1000sec is severely compromised by the fact that the > measurement setup is in my home lab which sees temperature swings of up to > 20 degrees C and which does get bumped from time to time. Longer runs in a > more controlled setting forthcoming). I can offer an explanation for the large effect of the zero correction seen here. The LTC2140 is specified to have a +/-10µV/°C drift (at 1Vpp setting). Converted into phase error due to zero crossing shift, this turns into a phase shift of +/-1ps/°C @ 10MHz. Note, the shift is given as +/- and per channel, which means, it could very well be that the channels are not matched in their temperature characteristics and thus the total phase shift could be +/-2ps/°C ... though total shift being closer to 0.5ps/°C is more likely. Summa sumarum: DC offset correction is important if a zero crossing detector is used. Attila Kinali -- <JaberWorky> The bad part of Zurich is where the degenerates throw DARK chocolate at you. _______________________________________________ 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.