Impact of Discontinuity in the Ground on the Signal Integrity of 100G PAM4 Ethernet

In high-speed SerDes, the ground return current plays a critical role in the signal transmission and can negatively affect the signal quality and stability of the system. Discontinuity in the ground will result in an impedance mismatch between the ground planes of different components or subsystems, leading to increased noise, crosstalk, and reflections that significantly degrade the performance of high-speed SerDes. To address this issue, presented is the importance of a well-defined return current path in 100G PAM4 Ethernet through the modeling of package along with board using a 3D Electromagnetic simulation tool. The results provide insight into the effects of resonance and crosstalk, helping designers to avoid mistakes in their designs. Overall, this work is an attempt to provide design engineers with a better understanding of the importance of ground in high-speed SerDes and the steps that need to be taken to ensure reliable and high-performance operation. By incorporating design rules pertaining to ground in the layout, engineers can ensure that their designs are robust and meet the specification for high-speed electrical standards.