MULTIMODE - a powerful code for frequency spectrum computation of electromagnetic fields in axially symmetric cavities and longitudinally homogeneous waveguides of arbitrary shape

This paper describes the MULTIMODE code for computing the lowest eigenfrequencies and electromagnetic fields in homogeneous waveguides and axially symmetric cavities. Eight-node isoparametric finite elements are used, which give the exact approximation of curvilinear region boundaries and high accuracy in computations of frequencies on a small number of grid nodes. The comparison of MULTIMODE with other programs shows that MULTIMODE attains the same accuracy while running 10-100 times faster. The program allows the computation of both simple and degenerate frequencies. (orig.)