Analysis of natural frequencies of cavities and scatterers using an impulsive current model

The formulation of Leviatan et al. (1988) is used to compute the complex natural frequencies of three-dimensional cavities and scatterers. The main idea is to expand the field inside the body and the field scattered from the body by means of the field of impulsive current sources (elemental dipoles) situated a distance away from (rather than on) the boundary. The key feature of this approach is that the fields anywhere in space can be evaluated analytically. This feature facilitates a substantial saving of computation time in comparison with standard on-surface formulations which involve integrations over surface currents when computing the fields. The computer program described by Leviatan et al. has been adapted for the computation of the real natural frequencies of a conducting spherical cavity, the complex natural frequencies of a conducting spherical scatterer, and the complex natural frequencies of a material spherical body. Numerical results are presented.<>