Exact Eigenfrequencies in Concentric Prolate Spheroidal-Spherical Metallic Cavities

In this letter the eigenfrequencies in prolate spheroidal-spherical and spherical-spheroidal cavities are calculated. The metallic boundaries of the cavities are perfect conductors. The matrix equations are constructed using expansions connecting the spherical and the spheroidal eigenvectors. Then, by truncating the resulting matrices, the exact eigenfrequencies are obtained as the converged roots of determinantal equations. This method allows to study elongated spheroidal cavities that existing methods fail to handle. The method is validated by comparison with published results from the literature. Original results for spheroids having large eccentricities are given for various values of the parameters.