The relationship between ground and EMI

Ground is an important concept in the PCB design. It provides return current path for both power and signal. Improperly grounding may cause EMI problem in PCB design. High impedance returns path brings the increment of EMI. Today, electronics engineers meet with the problems that the size of the PCB is getting smaller and smaller so that large area grounding has become a challenge to them. This paper focuses on the simulation of high-speed transmission line´s grounding, illustrating the EMI due to improperly grounding. And after that, some methods are promoted to reduce EMI