SerDes Design Part 7: ERL vs RL, the Move Toward More-Effective Characterization Metrics

ERL report from HyperLynx SI/PI

Ever heard of ERL? If not, you soon will. Effective Return Loss (ERL) is a new metric for SerDes channel or package characterization. It’s emerging as the 802.3cd™ Task Force closes in on a new standard for 50 Gb/s, 100 Gb/s, and 200 Gb/s Ethernet.

Defined as “a figure of merit for the electromagnetic wave reflection from a device or a channel input or output,” ERL is replacing the traditional frequency-domain return loss (RL) metric. The new algorithm is similar to COM (Channel Operating Margin) and will be used for the following transmitter, receiver, and channel characterization protocols:

  • 50GBASE-CR, 100GBASE-CR2, and 200GBASE-CR4
  • 50GBASE-KR, 100GBASE-KR2, and 200GBASE-KR4

As shown in my latest paper, “Effective Return Loss, a new metric for SerDes Channel or Package Characterization,” ERL is a more efficient and accurate metric than the traditional RL and its associated mask. Best of all, only HyperLynx® offers ERL support!

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This article first appeared on the Siemens Digital Industries Software blog at