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

Bob Camp lists at rtty.us
Tue Aug 21 19:37:53 EDT 2012


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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