Prediction of radiated perturbations from currents inside slotted screens using a hybrid FEM procedure

Electronic systems use electric currents in its normal work, but these currents will also be the origin of radiated perturbations that could affect the performance of neighbor systems. Thus, these circuits are enclosed in some kind of envelope or shield, in order to reduce the amplitude of the perturbations produced by them. Nevertheless, the external envelopes must sometimes be slotted, in order to connect the covered circuit to the exterior world (the expansion slots in PCs are a very common example). Unfortunately, these slots will radiate some electromagnetic perturbations, but an accurate design can keep them under critic values. As is shown, traditional models based on aperture antennas can fail when some effects (like edge effects) are not negligible, so a numerical approach is needed. The problem of slotted screens has been studied in the past from the point of view of electromagnetic susceptibility (EMS) using different numerical techniques. A number of have authors presented a hybrid procedure based on the finite element method (FEM) and modal analysis that was successfully applied to the study of EMS problems in slotted envelopes. In this work, this procedure has been adapted for solving the electromagnetic interference problem.