Network properties of discontinuities in multi-mode circular waveguide

The paper snmmarizes theoretical techniques for the evaluation of the network parameters of obstacle and aperture discontinuities situated in a uniform multimode waveguide. The formulation is valid for arbitrary waveguide cross-sections and for any finite number of propagating modes. After the rigorous formulation of the network parameters in the form of a scattering matrix, various approximate methods are described which lead to explicit expressions for the matrix elements, namely variational procedures, `equivalent stored energy¿ techniques and small-obstacle approximations. In a forthcoming paper, these techniques are applied to a variety of discontinuity structures in circular waveguide and the results are compared with experiment.