[SI-LIST] Re: Fibre channel interconnect margins
- From: "Alfred P. Neves" <al.neves@xxxxxxxxxxx>
- To: <a.ingraham@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 17 Jul 2006 12:48:23 -0700
Andrew,
Did you miss my point? Peak-peak jitter is ill-defined as are many
mathematical functions we are all familiar with, and the way we get
around this by constraining our estimate of TJ for a linear region past
the BER.
So, 0/0 is undefined, but lim x--->0 for sinx/x is defined, and TJ(BER)
is an ill-defined (not undefined) function. Question: is y=|x| a well
behaved function? Is it defined at x=0?
A useful example of dealing with the abstraction of limits applied to
jitter is that an infinite number of DJ sources generate a process
strictly defined by RJ. Ok, how many DJ sources can we almost say
result in a RJ dominated process? The mathematician would say
infinite, but they don't have to ship product (not true for the guys
working on Matlab code) and accordingly think differently than us
engineers. The answer is what BER region is of interest and what is the
linearity of this function past that region.
Andrew, I was tactfully trying to say we engineers often try to make
deterministic oversimplifications of a stochastic world due to the level
of abstraction involved. This is a rough generalization, not intended
to offend.
Alright, new rule from Scott:
Le'McCallan or Li'Chevas Rule, my personal favorite Li'Smirnoff rule.
Alfred P. Neves <*)))))><{
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-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Andrew Ingraham
Sent: Monday, July 17, 2006 10:53 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Fibre channel interconnect margins
> Maybe the safest approach to return to the mathematics. An
interesting
> perspective is the limit of sinx/x when x-->0? It is 1, but does not
> equal 1. sin(0)/0=0/0=0 doesn't it?
No it doesn't. 0/0 is undefined, it has no value.
0/n = 0, EXCEPT when n is 0. m/0 is undefined for any m.
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