Finite‐element analysis of three‐dimensional waveguide transfer problem‐application to coaxial line system

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AbstractAs a numerical solution of the electromagnetic waveguide transfer problem with a three‐dimensional discontinuity, the solution in which the finite‐element method is applied to the electromagnetic field at the discontinuity while the eigenmode expansion method is applied to the field in the waveguide is a powerful one. In such a solution, a method for connecting the electromagnetic fields in the waveguide to those in the discontinuity must be considered.This paper proposes a method in which the Galerkin method using the waveguide modal functions as the weighting functions is used for connecting the field on the boundary between the waveguide and the discontinuity. Since the connecting boundary can be taken very closely to the discontinuity in this method, the size of the matrix equation to be solved is small so that the amount of computation is small. There is no restriction between the number of expansion basis of the field by the finiteelement method and that of expansion modes in the eigenmode expansion method. Also, the matrix equation to be solved is symmetric. the matrix to represent the scattering at the discontinuity can directly be analyzed numerically.The method is applied in this paper to the simplest discontinuity problem in an axisymmetric coaxial line system to verify the validity of the method.