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[802.3_10SPE] Multidrop MDI return loss edit homework comment 425



After discussing with Piergiorgio and David Brandt, and looking at other BASE-T clauses, we determined that a figure was not necessary, but the reference impedance needed to be specified as a the two 100 ohm end terminations in parallel.

 

The result is the following proposed response:

Here is the new proposed response:

Change “In multidrop configuration the MDI shall be terminated by two 100  (nominal) impedances satisfying Equation (147–6) when measured with 100  ±1% impedance at the edges.”

To

“In multidrop configuration, the differential impedance at the MDI for each transmit/receive channel shall be such that any reflection due to differential signals incident upon the MDI from a balanced cabling terminated at both ends by 100 CAP OMEGA, and having a nominal differential characteristic impedance of 100 CAP_OMEGA, is attenuated, relative to the incident signal as per the relationship shown in Equation (147–6): “

 

(where CAP_OMEGA is capital omega)

 

For reference, here is the comment and the original proposed response:

 

Cl 147 SC 147.9.2.1 P 152 L 9 # 425

Comment Type T

MDI return loss specifies the termination. Requiring the termination of the MDI would

specify an implementation.

SuggestedRemedy

Change "In multidrop configuration the MDI shall be terminated by two 100 ? (nominal)

impedances

satisfying Equation (147-6) when measured with 100 ? ±1% impedance at the edges." to

"The MDI return loss (RL) shall meet or exceed Equation (147-6) for all frequencies

specified (with 100 ? ± 0.1 % reference impedance) at all times when the PHY is

transmitting data."

PROPOSED ACCEPT IN PRINCIPLE.

Change "In multidrop configuration the MDI shall be terminated by two 100 ? (nominal)

impedances satisfying Equation (147-6) when measured with 100 CAP_OMEGA ±1%

impedance at the edges." to "The MDI return loss (RL) shall meet or exceed Equation (147-

6) for all frequencies specified (with 100 CAP_OMEGA ± 0.1 % reference impedance) at all

times when the PHY is transmitting data."

Notes:

- CAP_OMEGA is capital omega

- spaces before CAP_OMEGA and ± are non-breaking

 

George A. Zimmerman, Ph.D.

President & Principal Consultant

CME Consulting, Inc.

Experts in PHYsical Layer Communications

1-310-920-3860

george@xxxxxxxxxxxxxxxxxxxx

 


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