A NEW BOUNDARY INTEGRAL APPROACH TO THE DETERMINATION OF THE RESONANT MODES OF ARBITRARILY-SHAPED CAVITIES

We present an efficient algorithm to determine the resonant frequencies and the normalized modal fields of arbitrarily shaped cavity resonators filled with a lossless, isotropic, and homogeneous medium. The algorithm is based on the boundary integral method (BIM), The unknown current flowing on the cavity wall is considered inside a spherical resonator, rather than in free-space, as it is usual in the standard BIM, The electric field is expressed using the Green's function of the spherical resonator, approximated by a real rational function of the frequency, Consequently, the discretized problem can be cast into the form of a real matrix linear eigenvalue problem, whose eigenvalues and eigenvectors yield the resonant frequencies and the associated modal currents, Since the algorithm does not require any frequency-by-frequency recalculation of the system matrices, computing time is much shorter than in the standard BIM, especially when many resonances must be found.