Simulation/experimental analysis of single/differential signals crossing splits

Abstract

It is known that high-speed single-ended signals crossing a split is not a good practice for EMI and signal integrity (SI) due to interruption of return current. However, it is becoming difficult sometimes to avoid this scenario due to small PCB form factor, i.e., tight routing density. When high-speed traces cross the split, stitching capacitors are placed right next to the crossing point. This paper shows that crossing split increases the overall radiation. In addition, the stitching cap reduces the radiation. However, the effectiveness of the stitching capacitor varies according to implementation. A simulation and experimental analysis is done to show that crossing the spilt is not appropriate for EMI/SI. In a similar manner, an experimental and simulation analysis is done for differential signals to understand the EMI and SI impact when crossing split.