Simulation for reduction effect on electromagnetic noise radiation using board-edge capacitors

Effects of capacitors at board edges on electromagnetic noise radiation are analyzed by simulation using the method of moments (MoM). The capacitors are connected to a power and a ground plane. The results show that the board-edge capacitors shift the radiation peak frequency toward higher range and reduce the peak intensity. The capacitance dependencies of the peak frequency and the intensity are classified into high and low capacitance group. This property is explained in terms of the distributed-parameter line theory. In the high capacitance group, the board-edge capacitors act as short terminals. They weaken the resonant current on the board and reduce the noise radiation