Date of Award

Spring 1997

Project Type

Dissertation

Program or Major

Engineering

Degree Name

Doctor of Philosophy

First Advisor

Kent Chamberlin

Abstract

A hybrid modeling technique using the Finite-Difference Time-Domain (FDTD) approach in conjunction with the Method of Moments (MoM) approach was developed to allow simulation of electromagnetic interference (EMI) emissions through apertures due to sources within a shielded enclosure. These apertures can include air ventilation openings, option card slots, mating cover seams, or any other opening in the metal shielded enclosure. Modeled emission results can now be directly compared to U.S. and other countries' regulations to allow engineers to predict compliance before hardware prototypes are built. The effects of the test environment, including ground plane and specified measurement distance, as well as configuration requirements, such as long attached wires, are included and result in more accurate models of the real-world environment than previously possible.

The first stage of the hybrid technique uses the FDTD approach to model the source within the shielded enclosure and to find the electric fields within the aperture or apertures. The sources within the enclosure include printed circuit board traces, internal wires and cables, and discrete devices, such as integrated circuits and heatsinks. Errors in the aperture fields at low frequencies due to limitations in the FDTD absorbing boundary conditions are then corrected using an extrapolation technique. Once the electric fields within the aperture are known, they become the source for the second stage of the hybrid technique. This second stage uses MoM to find the external fields while including the effects of long attached wires, ground planes, and a distant receive location. The results from the second stage can then be compared to the various regulatory agency requirements.

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