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

Bob Camp lists at rtty.us
Wed Aug 22 11:57:58 EDT 2012


Hi

It depends very much on just how low a frequency sine wave you put into the
limiter. If you run low enough, then indeed you will be able to see the
difference. If the scope can display 1 ns jitter, then a 1 Hz sine wave is
likely to be low enough.

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Azelio Boriani
Sent: Wednesday, August 22, 2012 5:55 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Understanding Oliver Collins Paper "Design of Low
Jitter Hard Limiters"

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
> >
> >
> >
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