-----Original Message-----
From: Pat Thaler
[mailto:pat_thaler@AGILENT.COM]
Sent: Monday, August 22, 2005 3:01
PM
To:
STDS-802-3-BLADE@listserv.ieee.org
Subject: Re: [BP] Recommended
material and connectors
Brian, it is a good question, but this
reflector is for development of the standard rather than advice to
implementors.
Ayal, the IEEE 802.3ap website has a
public area with all the presentations that have been made to the task force.
You might take a look at that for the investigations into the backplane
materials that were made to determine the channel model.
www.ieee802.org/3/ap
Regards,
Pat
From: Brian Seemann
[mailto:brian.seemann@XILINX.COM]
Sent: Monday, 22 August, 2005
11:34 AM
To:
STDS-802-3-BLADE@listserv.ieee.org
Subject: Re: [BP] Recommended
material and connectors
Hi Ayal,
You have asked a very simple, reasonable
question. The amount of time and energy that the 802.3ap contributors
spent on this is staggering. But over the past several years, we have
learned a great deal about the role of materials and connectors in high speed
signal integrity. A large amount of this work has been contributed in
IEEE 802.3ap.
Here are some points that address some
aspects of your question:
·
In general, the industry has moved forward
significantly in what can be done with mainstream materials, connectors and
manufacturing processes.
·
The IEEE 802.3ap standard specifies the
performance of the transmitter and the receiver. This is what will
ultimately determine the channels servable by the standard.
·
The channel model (Section 69.3) is informative
only, to give guidance to backplane builders for what will likely work and not
work with the transceivers.
·
The standard will not specify or even recommend
particular connectors, materials or construction methods.
·
Careful layout design techniques are probably the
most performance-effective and the most cost-effective measures to ensure
signal integrity.
·
There are 10Gbps-capable connectors available
from several manufacturers.
·
The performance of good connectors can be
completely obscured by poor layout design methods.
·
There are multiple contributions showing
successful 10Gbps performance on materials such as Nelco 4000-13, Nelco
4000-13SI, and Isola FR408. Again the standard will not make any
recommendations about materials.
·
In many cases on the line cards, lower grade
(higher loss) board material (such as 4000-6) has actually been shown to be
preferable to higher grade (lower loss) material. This is because higher
loss can reduce the Q (reflection effect) of stubs.
·
The performance of good material can be
completely obscured by poor layout design methods.
·
Vias from top layer traces are probably the most disruptive
layout feature to signal integrity.
·
Backdrilling vias to eliminate the stub is viewed
by many manufacturers as cost feasible.
Others
on this reflector can weigh-in with more insightful or alternative
perspectives.
Brian Seemann
From: Ayal Lior
[mailto:Ayal.Lior@tera-chip.com]
Sent: Monday, August 22, 2005 8:54
AM
To:
STDS-802-3-BLADE@listserv.ieee.org
Subject: [BP] Recommended material
and connectors
Hi,
I am new to this reflector and have a very basic question.
We would like to know what is the recommended material and
connectors for backplane to drive the 10GBase-KR.
Target application is chassis with maximum length of
40" with two connectors.
Any feedback is appreciated.
Thanks,
Ayal Lior