Effect of the Geometry of Slots and Splits on EMI Level of PCBs: A Parametric Study

A defect on the reference plane, when crossed over by a signal trace on the signal line, is a primary source for unwanted electromagnetic radiation in printed circuit boards (PCBs). Such a defect either completely cleaves the reference plane into two pieces by means of forming a split between them or partially divides the reference plane by means of forming a slot with a short on at least one end of the defect. This paper presents a detailed parametric study on these defects focusing on how electromagnetic interference (EMI) level varies as a function of geometric parameters. In this regard, first, the width of a slot and a split is systematically varied, and electric field at 3 m away from the PCB is simulated, by keeping the lengths of the slot and split constant. Then, the same simulations are repeated by keeping the width constant and varying the length of the defect. Simulation results show that the length of the defect is an ultimate determinative parameter in the radiation characteristics of the defect. The measurement results for two PCBs; one with a slot and another with a split on the ground plane are also presented.