EMC coupling to a circuit board from a wire penetrating a cavity aperture

The analysis of printed circuit boards (PCBs) is a problem of recent interest. Of particular interest is the electromagnetic coupling from an exterior field to a circuit component on a PCB inside a conducting cavity (shield) via a direct connection from a wire or cable that penetrates an aperture in the cavity; indeed, this may often be the dominant coupling mechanism. An accurate and efficient analysis of this EMC problem requires the combination of PCB analysis with the analysis of field penetration into a cavity via a penetrating wire, and this is the subject of the present investigation. A hybrid technique for calculating the signal level at the input to a device on a PCB due to an exterior field incident on the cavity is discussed. The technique separates the analysis of the cavity/wire from that of the conductor trace on the PCB, thus enabling an efficient calculation. The method allows a The´venin equivalent circuit to be obtained at any point on the PCB, such as a point where the PCB conductor trace meets a circuit component of interest on the PCB.