Design and simulation of a 20 Gbps communication channel

Abstract

Digital wire-line communication speeds are increasing rapidly to achieve ever higher data rates. Speeds beyond 20Gpbs are desirable for the next generation of protocols. However, higher frequency signals experience more loss due to the physical channel and are more sensitive to small imperfections in the channel, such as vias. In this work, an existing communication channel between two controller boards across a midplane was improved to allow for operation at a higher frequency. Mentor Graphics HyperLynx was used to simulate the channel and display S-parameter models and eye diagrams to demonstrate the impact of various designs. The effects of the material properties, impedance of the traces, and vias were simulated and the results combined to determine what physical layer improvements must be made to reduce loss and reflections at this high frequency.