Paving the Way for 400Gb Ethernet and 5G


Reading time ( words)

This article briefly introduces the 4-level pulse amplitude modulation (PAM-4) and its application in 400 Gigabit Ethernet (400GbE), to support the booming data traffic volume in conjunction with the deployment of 5G mobile communications. Furthermore, this article also highlights the essential pre-layout effort from signal integrity perspective for physical (PHY) link design on a PCB, including material selection, transmission line design and channel simulation to support 56Gbps data rate that paves the way for seamless communication in 400GbE.

I.  Introduction

400GbE is a new wired communication standard to accommodate the booming data traffic volume with the implementation of 5G mobile communications. In the implementation of 400GbE communication, electrical interface with 4-level pulse amplitude modulation (PAM-4) signaling over 8 lanes is adopted. The communication of eight lanes at 56Gbps (i.e., 28GBaud) per lane enables the total bandwidth of 400Gbps over the Ethernet. The electrical specifications of 400GbE with PAM-4 signaling are defined in IEEE 802.3bs.

PAM-4 has 4 digital amplitude levels, as shown in Figure 1. It has an advantage over non-return-to-zero (NRZ) signals because each level or symbol in PAM-4 contains two information bits providing twice as much data throughput for the same baud rate. For instance, 28GBaud is equivalent to 56Gbps in PAM-4 and 28Gbps in NRZ respectively.

II.  Essential pre-layout effort from signal integrity perspective

According to guidelines, a PAM-4 channel with trace length up to 8 inches on a PCB shall have insertion loss less than 10dB at 14GHz (i.e., Nyquist frequency of 28GBaud) and 20dB at 28GHz (i.e., 2nd harmonic of 28GBaud) respectively to achieve seamless data communication between the transceivers.

To read this entire article, which appeared in the May 2018 issue of Design007 Magazine, click here.

Share

Print


Suggested Items

Words of Advice: What Feature Would You Like to See in Your CAD Tool?

05/30/2019 | Andy Shaughnessy, Design007 Magazine
In a recent survey, we asked the following question: What feature would you like to see in your CAD tool? Here are a few of the answers, edited slightly for clarity.

Altium’s Craig Arcuri on Design Rules: Past, Present, and Future

05/28/2019 | Andy Shaughnessy, Design007 Magazine
We recently spoke with Altium’s Craig Arcuri about his views on design and manufacturing rules. Craig has experience running both design and manufacturing companies, so he has a fairly circumspect view of constraints from both sides of the product realization process. Craig details some of the challenges with setting and managing hundreds of often divergent design and manufacturing rules, and how both design and manufacturing constraints need to evolve.

XNC Format: Gerber Takes Data Into the Future

05/20/2019 | Denis Morin, Karel Tavernier, Jean-Pierre Charras, and Marius Matioc
The problem is that so many NC files are of deplorable quality because the NC format was never designed as a data transfer format. It has always been a machine driver and contains all sorts of information that a drilling machine needs, but that is irrelevant and confusing for data exchange.



Copyright © 2019 I-Connect007. All rights reserved.