Shielded air vent design guidelines for EMI modeling

The development of a numerical analysis tool to perform EMI (electromagnetic interference) modeling on air vent panels and slots in shielded cabinets and other devices is described. A set of design guidelines was developed from that tool. The model uses the realistic source of a current on a wire inside the openings (rather than a far-field plane wave, as is often used). It can predict the received field strength at typical FCC distances due to these openings. The model allows the size, depth, number, spacing, and orientation of the air vent holes to be varied. The model has been used on a wide range of product configurations (with various currents and frequencies) and different air vent and slot configurations. Rapid comparisons between existing and proposed vent design as well as tolerance analysis can then be performed