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Effective Return Loss for 112G and 56G PAM4

Richard Mellitz (Distinguished Engineer, Samtec)

Location: Ballroom B

Date: Wednesday, January 31

Time: 11:00am - 11:45am

Pass Type: 2-Day Pass, All Access Pass, Alumni All Access Pass - Get your pass now!

Track: 04. System Co-Design: Modeling, simulation and measurement validation

Audience Level: Intermediate

Format: 45-Minute Technical Session

Vault Recording: TBD

Audience Level: Intermediate

This paper proposes using a pulse echo for time domain reflectometry (TDR) rather the commonly used step function echo. The echoed pulse response of a single symbol is convolved with the modulation signal levels to produce an effective reflection coefficient metric at a specified bit error ratio (BER). A conversion to dB presents effective return loss (ERL) in more familiar return loss units. ERL is a single value which replaces the commonly used frequency domain return loss (RL) masks. It makes RL grading simple, straightforward and meaningful.


Classic return loss masks are be too restrictive for realistic PAM4 product designs.
ERL is a single number representing return loss statically computed from pulse TDR. The pulse represents a single symbol.
ERL is the future for return loss metrics.
ERL is easy use in quick design engineering estimations.

Intended Audience

Knowledge of frequency domain loss measurements, simulation, and signal integrity would be helpful.