Re: [SI-LIST] : 2.5 Gbps across a backplane

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From: DORIN OPREA (dorin.oprea@alcatel.com)
Date: Tue Oct 17 2000 - 05:52:05 PDT


Hi,

Can somebody describe in detail the way the equalization is done ?
Are the equalizors ICs or filters ? What is the name of the device ?

Thanks,
Dorin

"Dr. Edward P. Sayre" wrote:

> Folks:
>
> A subtle issue came up in the recent T11 (Fibre Channel) meetings. How do
> you spec an interconnect when adaptive equalization parts will be used to
> dig out the signal? If you have really good eye-diagrams response then do
> you need equalization? Conversely, if you need equalization because of
> excessive deterministic jitter (read that insufficient rise time bandwidth)
> or eye closure (read that too much attenuation) or both, then what
> constitutes an acceptable way to specify the interconnect, be it backplane,
> cable or connector?
>
> Now, the question of cross talk corruption of the signals is another
> matter, especially when equalization is involved. Cross talk can be of no
> consequence or it can be of terrible consequence, especially if there is a
> requirement for byte (a 4 bit nibble) aligned serial data streams. Our
> work indicates that connector cross talk in differential connectors appears
> to be essentially dV/dt noise due to any asymmetries in the geometry of the
> connector or interconnect (vias count here!). Although small, and
> generally in the (1 - 4%) range, it is obviously a problem when many lines
> are switching and especially if the time alignment is not within a small %
> of the rise time between individual differential components. If the signal
> is broken into its even (common mode) and odd (differential) mode
> components, it can be shown that very soon the common mode cross talk
> dominates the cross talk.
>
> So, when is cross talk an equalization issue from a differential eye
> diagram point of view; and can equalization help from an EMI point of view?
> I look forward to folks' ideas on this matter.
>
> ed sayre
>
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> | NORTH EAST SYSTEMS ASSOCIATES, INC. |
> | ------------------------------------- |
> | "High Performance Engineering & Design" |
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> | Dr. Ed Sayre e-mail: esayre@nesa.com |
> | NESA, Inc. http://www.nesa.com/ |
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