NUMERICALLY EFFICIENT COMPUTATION OF A COMPLETE SET OF EIGENFUNCTIONSIN COMPLEX CAVITIES

It is demonstrated, that both the divergence-free resonance modes and the irrotational electric and magnetic eigenfunctions are necessary fo r a rigorous modal expansion in complex cavities. A numerically effici ent computation of the irrotational eigenfunctions based on the genera lized scattering matrix technique is presented. A systematic searching strategy for the cavity eigenfunctions which is based on Foster's the orem is discussed. Finally two improvements of the modal expansion are suggested which significantly increase the accuracy and the numerical efficiency of this method, namely, the removal of the non-uniform con vergence of some field series at the coupling apertures and the estima tion of the asymptotic values of some slowly converging series related to the modal expansion.