20140210_28Gbps PCB design

There’s nothing simple about getting 28Gbps serial channels working in a real system design. “The challenges of a 28Gb/s channel in support of 100 GB Ethernet are no different than the original problems of the 1st trans-Atlantic copper communication cable where transmission line theory dominates and the control of frequency dependent losses along with reflections are the key to success.” That’s how the DesignCon 2014 paper titled “De-Mystifying the 28 Gb/s PCB Channel: Design to Measurement” by Jack Carrel, Heidi Barnes, Robert Sleigh, Hoss Hakimi, and Mike Resso begins. If you’re familiar with Lord Kelvin’s work on the first trans-Atlantic cable exactly 160 years ago, then you know exactly what these authors from Agilent and Xilinx mean.

在一个真正的系统设计中让28Gbps串行通道正常工作，绝不是一件轻而易举的事情。“28Gbps通道支持一个100GB以太网的的挑战，和铺设第一条跨大西洋铜通信电缆的挑战没什么分别，同样都是传输线理论占主导和与频率相关的反射损耗控制是成功的关键。

这也就是为什么DesignCon 2014一篇题为“28Gbps PCB通道设计揭秘：设计始于测量”（De-Mystifying the 28 Gb/s PCB Channel:

Design to Measurement， 作者：Jack Carrel, Heidi Barnes, Robert Sleigh, Hoss Hakimi,和Mike Resso。）的论文发表的原因了。如果你熟悉160年前开尔文勋爵的第一个跨大西洋电缆项目，你就会真的明白这些来自安捷伦和赛灵思公司作者们的意思了。

The paper describes the construction of a pcb that conveys 28Gbps signals from a Xilinx FPGA to a board connector for attachment to an external device. The paper then focuses on developing test structures and conducting analysis to permit the “de-embedding” of the test structures to build an accurate picture of the real in-system behavior of the system being tested. Here’s a closeup of a section of the pcb:

这篇论文介绍了一种PCB的结构，它可把28Gbps信号从赛灵思的FPGA通过板卡连接器传输到外部设备。 该论文侧重于开发一种测试架构并进行分析，以便实现一种“非嵌入式”的测试架构，最终为被测系统建立一个真实系统级行为的精准描述，下面是PCB部分的局部放大图。

图2  VC7222 28Gbps内部带状线布线设计参数和结果细节

阅读该论文的全文，请点击：

http://www.xilinx.com/events/designcon2014/13_FR3Paper_DeMystifyingthe28gbsPCBChannel_v2.pdf