Sorry, I’ll be careful in future comments.
Dr. Edward P. Sayre, P. E,
9 Maple Lane
Marshfield, MA 02050
[T]: 781-837-9088
[C]: 978-314-4940
esayre@xxxxxxxx
From: Chad Jones (cmjones) <00000b60b3f54e8d-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Monday, March 24, 2025 1:06 PM
To: STDS-802-3-ISAAC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_ISAAC] Questions related to Conrad presentation on 03/24/2025
Reminder to Ed that we are individuals in 802.3, not representatives of corporations.
Regards,
Chad Jones
Principal Engineer, Cisco Systems
Executive Secretary, IEEE 802.3 Working Group
Chair, IEEE P802.3da Task Force
Principal, NFPA 70 CMP3
To my colleagues:
I agree with Marvel that this matter demands further investigation from both a fundamentals point of view as well as the usage of interconnect tools which combine chip models with properly specified transmission line models.
I believe that the past reliance on overly simplified cable models does not contribute to a full understanding of the signaling and error performance between the Tx and Rx chip I/O signals and the multi-wavelength long cable effects on
those signals. We know from the significant past work that 10 sections per wavelength, in this case, the wavelength of the data Nyquist frequency (adjusted for interconnect relative dielectric constant) is necessary for the accurate determination of impedance,
Insertion Loss and Return Loss using a lumped constant model (or it’s functional equivalent as expressed in the tool used). Consideration of the use of the COM tool is also recommended.
Sincerely,
Ed
Dr. Edward P. Sayre, P. E,
President and CTO
North East Systems Associates, Inc.
9 Maple Lane
Marshfield, MA 02050
[T]: 781-837-9088
[C]: 978-314-4940
esayre@xxxxxxxx
Hi Conrad,
Can you please clarify how you were able to construct a cable that has 3dB higher echo when combined with the MDI than the echo from the cable itself?
You mentioned verbally that your analysis assumed lumped elements. It would be great if you could share the characteristics of the lumped elements you assumed.
Ragnar
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