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Effective Return Loss for 112G and 56G PAM 4


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2/28/18 11:00 am to 12:00 pm EST

Event Description

Signal Integrity Webinar Series

Title:  Effective Return Loss for 112G and 56G PAM 4

Date:  February 28, 2018

Time:  8am PT/ 11am ET

Presented By:  Richard Mellitz, Distinguished Engineer

Sponsored by:  Samtec


This presentation 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 results in an 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) mask. It makes RL grading simple, straightforward and meaningful.

Table of Contents:

  • Background
  • Problem Statement
  • Relation to PAM
  • Introduction to Pulse Time Domain Reflectometry (PTDR)
  • Effective Return Loss (ERL) Computation
  • Channel Reflection Experiments
    • Developing Channel design Guidelines
  • Mapping performance to ERL
  • Impact of a Receiver Capability
  • ERL Summary

Presenter Bio:

Richard Mellitz is presently a Distinguished Engineer at Samtec, supporting interconnect signal integrity and industry standards. Prior to this, he was a Principal Engineer in the Platform Engineering Group at Intel.  Richard was a principal member of various Intel processor and I/O bus teams including Itanium®, Pentium®, PCI Express®, SAS®, and Fabric (Ethernet, IB, and proprietary).  Additionally, he has been a key contributor for the channel sections IEEE802.3 backplane and cabling standards, and for the Time domain ISI analysis for IEEE802.3 Ethernet, known as COM (Channel Operating Margin), which is now an integral part of Ethernet standards due to Rich’s leadership.  He founded and chaired an IPC (Association Connecting Electronics Industries) committee delivering IPC’s first PCB loss test method. Prior to this, Rich led industry efforts at IPC to deliver the first TDR (time domain reflectometry) standard which is presently used throughout the PCB industry.   Richard holds many patents in interconnect, signal integrity, design, and test. He has delivered numerous signal integrity papers at electronic industry design conferences. In 2017 he was awarded the IEEE SA Standards Medallion.