[time-nuts] Understanding Oliver Collins Paper "Design of Low Jitter Hard Limiters"

Azelio Boriani azelio.boriani at screen.it
Wed Aug 22 09:44:10 EDT 2012


According to

http://cp.literature.agilent.com/litweb/pdf/5989-8794EN.pdf

the real time sampling scope (like the TDS220 or TDS3012) can measure cycle
to cycle jitter directly, whereas the equivalent time sampling has only one
sample each trigger and a little delay on the sampling point for the next
trigger. The displayed waveform is a sort of "sum" of more than one cycle
and now I can't figure out what type of picture this can give. The TDS3012
has also the advantage of the Digital Phosphor behavior that can be useful
for the jitter analysis. Maybe a stable timebase and low jitter external
trigger input are essential. Unfortunately the TDS3012 has a 200ppm
timebase...

On Wed, Aug 22, 2012 at 2:54 PM, David <davidwhess at gmail.com> wrote:

> Do you mean with a 7404 hex inverter?  I actually did something like
> this recently while adding a 75ns pre-trigger pulse to an existing
> fast rise pulse generator.
>
> The pre-trigger pulse ended up having significant pattern dependant
> jitter caused by the adjacent TTL divider chain modulating the supply
> voltage and the poor power supply rejection of the 7404.  I was easily
> able to see the jitter on my 7T11 sampling oscilloscope but on my 2440
> (20 GS/sec equivalent time sampling), it was barely perceptible if
> that despite ideal conditions.  The peak to peak jitter was about
> 100ps.
>
> As far as I could tell from the available online documentation, the
> TDS220 and TDS3012 have relatively low sample rates and do not support
> equivalent time sampling so I would expect them to show even less than
> my 2440.
>
> On Wed, 22 Aug 2012 11:55:11 +0200, Azelio Boriani
> <azelio.boriani at screen.it> wrote:
>
> >In your opinion, if I build a 7404 ZCD and a hard limiter one, can I see
> >the jitter difference on a simple 'scope (Tek TDS220 or TDS3012) or do I
> >need the Wavecrest SIA3000?
> >
> >On Wed, Aug 22, 2012 at 1:37 AM, Bob Camp <lists at rtty.us> wrote:
> >
> >> Hi
> >>
> >> Since the Collins approach "tunes" the system for a single frequency
> input
> >> (more or less), the approach is probably not the best for a "many
> decades"
> >> sort of frequency range. There are a number of things that he alludes
> to in
> >> the paper, but does not directly address. The most obvious is the
> >> temperature dependance of the "stuff" the system is made of. Another is
> the
> >> simple fact that a non-clipping linear amplifier is likely the best
> choice
> >> for a first stage, provide the input is not already near clipping.
> >>
> >> Bob
> >>
> >> On Aug 21, 2012, at 12:50 PM, raj_sodhi at agilent.com wrote:
> >>
> >> > Hello everyone,
> >> >
> >> > I am new to this forum.
> >> > It looks like a lively discussion on various topics.
> >> >
> >> > A colleague of mine here at Agilent pointed me to this paper entitled
> >> "The Design of Low Jitter Hard Limiters" by Oliver Collins. In Bruce
> >> Griffiths' precision time in frequency webpage, this paper is described
> as
> >> "seminal."
> >> > (http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)
> >> >
> >> > Since I'm trying to create a limiter that will accept frequencies
> >> ranging from 1 MHz to 100 MHz, I thought it would be good to understand
> the
> >> conclusions of this paper (if not the mathematics as well).  The
> >> mathematics turned out to be quite challenging to decode. Has someone on
> >> this forum unraveled the equations? It appears Collins has
> recommendations
> >> on the bandwidth and gain of a jitter minimizing limiter, and then
> extends
> >> this analysis to provide the bandwidth and gain of a cascade of
> limiters.
> >>  But the application is still fuzzy.  In figure 5, he shows a graph
> showing
> >> the dependence of jitter on crossing time.  Is the crossing time
> (implied
> >> by equations 7) considered a design parameter one can vary? Also, on
> figure
> >> 4, the "k" parameter has been varied to show the rising waveform as a
> >> function of "k".  The threshold is always assumed to be 0.5.  So could
> "k"
> >> be related to "tau", the time constant of the RC filter?
> >> >
> >> > Thanks in advance for all your help.
> >> >
> >> > Yours
> >> >
> >> > Raj
> >> >
> >> >
> >> >
> >> > _______________________________________________
> >> > time-nuts mailing list -- time-nuts at febo.com
> >> > To unsubscribe, go to
> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >> > and follow the instructions there.
> >>
> >>
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts at febo.com
> >> To unsubscribe, go to
> >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >>
> >_______________________________________________
> >time-nuts mailing list -- time-nuts at febo.com
> >To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>



More information about the time-nuts mailing list