Novel approach to the theory of longitudinally inhomogeneous lossy waveguides

In this paper a new approach to the analysis of irregular lossy waveguides is proposed. It allows us to reduce the problem to the set of ordinary differential equations similar to lossless case. It is based on scalar expansions, which are more flexible and, as a rule, have better convergence compared to the vector ones. It takes into account local lossy boundary conditions in a rigorous manner. It can be applied for a lot of waveguide structures with different cross-sections, with non-uniform and anisotropic filling, and so on. A brief description of the approach is presented below for the case of a circular waveguide with an azimuthally symmetric radius variation.