[802.3_NGAUTO] MDI Return Loss
I presented material in today's ad-hoc call on modifications to the MDI return loss.
http://www.ieee802.org/3/ch/public/adhoc/DenBesten_3ch_01_0719.pdf
Key messages: 1) make the MDI RL limit scale with speed to avoid overspecification of the lower rates and 2) modify/relax the high-frequency limit to improve feasibility without compromising receiver margin.
An important question that was asked is where the high-frequency dual-slope MDI return loss curve in the current draft stems from. As far as I know it came from this contribution in Spokane:
http://www.ieee802.org/3/ch/public/sep18/bhagwat_3ch_01a_0918.pdf
The MDI return loss limit seems to be constructed as a modified link return loss limit to accommodate for a higher return loss above Nyquist. However the mechanisms for both are different. The link segment return loss and MDI return loss are typically quite a bit different. As other contributions have pointed out the limit in the current draft is very strict so it seems we have to do something about it.
Looking forward to hear your feedback.
See you soon in Vienna.
Best regards,
Gerrit den Besten
Fellow, NXP Semiconductors, NL
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