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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
References: <3DC1D056.email@example.com> <3DC1F17C.D3149AB3@SpamMeSenseless.us.ibm.com> <3DC21367.7060908@BOGUS.earthlink.net>
Subject: Re: Who thinks this?
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X-Inktomi-Trace: public1-pete2-5-cust19.pete.broadband.ntl.com 1036138005 24108 184.108.40.206 (1 Nov 2002 08:06:45 GMT)
Date: Fri, 1 Nov 2002 08:06:44 -0000
NNTP-Posting-Date: Fri, 01 Nov 2002 08:06:46 GMT
"Chris Carlen" wrote in message
> Phil Hobbs wrote:
> > I'll leave the LC transmission line questions to others, and just
> > an observation about really fast interconnections: At very high
> > (2 Gb/s or higher), transmission lines on circuit boards really do
> > like distributed RC circuits, e.g. they slow down quadratically with
> > distance. The reason is basically copper losses and dielectric
> > absorption in common materials such as FR4 board. To get fast
> > to go any distance on a backplane, you have to do all sorts of ugly
> > preemphasis tricks to preserve bandwidth. In many instances, e.g.
> > IBM Regatta servers, fast logic signals are demultiplexed down into
> > several lines each to cross the board or backplane, then multiplexed
> > back up into the original logic line. Ugly but necessary--this
> > your dad's computer.
> > One reason computer companies (such as my employer) are looking at
> > optical interconnections is that the bandwidth can be preserved over
> > much longer distances.
> Interesting. That indicates a case that is far from ideal, unlike
> I am conjecturing about.
> I'd like to master the totally general simulation of transmission line
> wave propagation, using the transfer function the whole way through.
> But at this point I only know how to do steady state AC, and
> propagation with real reflection coefficients and Zo.
> There's a lot to learn to really understand this subject. It's really
> case where if the mathematical tools aren't available,
Well, that's not really true. Spice3/XSpice has a generic RCLG
transmission line. You can simulate anything you want in time or the
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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