High-speed common-mode prediction method for PCBs having a signal line close to the wide ground edge

摘要

We have developed the prediction method of common-mode radiation from a PCB with a narrow ground plane. In this method, we use a parameter called the current division factor, which is related to the degree of imbalance. In this report, we apply this method to the microstrip structure in the vicinity of the wide ground edge. The calculated difference of EMI agrees well with measured one. And this method can predict the effect of the guard band, which is useful for EMI reduction to the microstrip structure in the vicinity of the ground edge.