Influence of the PCB Dielectric Material on the Coupling of PCB Traces to Enclosure Cavities

PCB structures like traces couple to the cavity field inside of an enclosure. It has been presented before that the coupling of a trace inside of a homogeneous cavity is caused just by its vertical segments on the trace ends. For an inhomogeneous cavity, consisting of a FR4 PCB layer and an air layer, we show that a trace couples along its whole length. The different coupling must be considered in the PCB design, for instance, for trace shielding. We present examples for a PCB trace coupling to a cubical enclosure, utilizing an efficient cavity model. Cavity mode; coupling; EMI; enclosure fields; shielding;