[time-nuts] Gate propagation delay jitter

Magnus Danielson cfmd at bredband.net
Tue Apr 10 18:35:21 EDT 2007


From: Enrico Rubiola <rubiola at femto-st.fr>
Subject: Re: [time-nuts] Gate propagation delay jitter
Date: Wed, 11 Apr 2007 00:14:01 +0200
Message-ID: <AD07B1AE-765F-471B-A549-7F09F023EC91 at femto-st.fr>

Enrico,

> > Then we would need to know/measure the jitter of the retiming  
> > flipflop.
> Expected values
> microwave: -120 dBrad^2/Hz flicker, -150 dB white
> RF:                -140 dBrad^2/Hz flicker, -150 dB white
> Use a double balanced mixer, traditional configuration.
> A correlation scheme is probably not  necessary.

So you mean I could toss in a double-balanced mixer and feed it with the
sampling clock and the output lines, while feeding the flip-flop some lower
clock? 

> On the understanding side, aliasing is the beast to kill.
> A logic gate shows a gain g<>0 (analog gain!!!) during the
> edges, for it behaves as a sampling system -> increased
> noise bandwidth, due to aliasing.

It is a sampling system. It is just that it attempts to gain out the signal to
be either high or low.

Wouln't meta-stability be an issue here?

> William Egan wrote an illuminating article, Transact. UFFC
> (1990 in my notebooks, 1992 in my memory, sorry)
> 
> > There appears to be little definitive published data on the jitter of
> > various logic gates and flipflops.
> I know.  Fred L. Walls did some work, proc. Freq. Control Symp,
> I don't remember when.

It is at times like this I am sad I don't have that access anymore. It was
too much money for me at the time.

Cheers,
Magnus




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