SOLVING MAXWELL EQUATIONS IN A CLOSED CAVITY, AND THE QUESTION OF SPURIOUS MODES

Maxwell's equations in a closed cavity govern processes like heat generation in a microwave oven, or signal transmission across a junction of complicated shape between two waveguides. They should not be solved by the “vectorial” analog of the classical finite-element method (that is, with node-based finite elements). There are good reasons to use edge-elements instead. Such elements (whose degrees of freedom correspond to the edges of the mesh, not to its nodes) not only guarantee the right kind of continuity for fields like h and e, they also prevent the appearance of unwanted, unphysical, divergent solutions in the problem of eigenmodes, the socalled “spurious modes”. © 1990, IEEE. All rights reserved.