Hi Raj, welcome. Thank you for joining the group and thanks to Magnus for his comment about the Collins' paper.
On Tue, Aug 21, 2012 at 11:51 PM, Magnus Danielson < [email protected]> wrote: > Hi Raj, > > > On 08/21/2012 06:50 PM, [email protected] 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) >> > > This is indeed a good paper to read. > > > 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). >> > > I agree that it could be very good to understand the paper for such a > design. > > > The mathematics turned out to be quite challenging to decode. Has >> someone on this forum unraveled the equations? >> > > Both Bruce and me have been looking deeply into this paper (even if it > where some time ago, so I re-read it quickly). Bruce deeper than me, but I > think I can guide you into it. > > > 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. >> > > You obviously have not paid attention to Chapter 1 where the application > is very clear and obvious. In particular Dual Mixer Time Difference (DMTD) > systems (of which one side is seen in Figure 1) is being discussed, but I > think it is equally valid in your application, as it relates to the overall > basic issue "Given a sine of a particular frequency, which limiter will > provide me with minimum trigger jitter?" > > > 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? >> > > Yes, k is the design parameter as the normalized crossing time. > > > Also, on figure 4, the "k" parameter has been varied to show the rising >> waveform as a function of "k". >> > > It essentially shows you how the filter bandwidth (as tau shifts with k) > will affect the output signal as a function of the design parameter k. > > > The threshold is always assumed to be 0.5. So could "k" be related to >> "tau", the time constant of the RC filter? >> > > That is formula 10. > > Actually, you can pick one of many different parameters as the one for the > one degree of freedom parameter, and he has chosen the normalized crossing > time k. Just about any other normalized parameter could have worked as well. > > Bruce observed that the same amount of contributed noise was assumed in > the Collins paper, so you would like to read his notes of: > http://www.ko4bb.com/~bruce/GeneralisedCollinsHardLimiterPaperV3B.pdf > > Oh, an interesting note is that the Collins paper considers what happens > on a single transition, so that's why it is relatively clean from input > frequency issues. What will change is the input slew-rate. > > The Collins paper does not very clearly advice you how to deal with 1:100 > input frequency design-range, even if it occurs as an example of variation, > just scalled down a million times from your design problem. > > Another possible critique on the Collins paper is that it only consider > white noise, and not flicker noise. For low frequencies, flicker would be > noticeable if not dominant, where as for higher frequencies the white noise > assumption works pretty well. > > Cheers, > Magnus > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
