The use of sidewalls on an image plane to reduce the radiated emissions from an electric line source

Abstract

The radiated emissions produced by electronic circuits are often reduced by placing pieces of metal in the vicinity of the current paths. Even when the metal does not carry return current directly, the conductive surface serves as an image plane which has been proven successful in mitigating common-mode emissions. Previous studies showed that a finite-width plane effectively reduces radiated emissions as long as the current source is not placed too close to an edge of the plane. This parametric study characterizes the effect of adding short vertical sidewalls at the edges of the plane to create a trough structure. The work quantifies the influence exerted by a small metal fence at the edge of an image plane on the emissions from a line source routed near an edge. The study is of interest to PCBs and off-board cables.