Higher modes in smooth irregular waveguides

The paper presents a theoretical analysis of the smooth transition between regular multimode waveguides, e.g., the smooth bend of a waveguide of constant width or the smooth junction between coaxial waveguides of different widths. The incident field is considered as the eigenmode of the left regular waveguide. The goal of the study is to calculate amplitudes of excited eigenmodes of the right regular waveguide and to determine the field within the transition. An asymptotic solution is obtained for an infinite system of equations for the amplitudes of propagating modes, under the assumption that the incident field has a high mode number and that reflected waves can be neglected.