Analysis of waveguides terminated in infinite flange by using modal field approach

The problem of analyzing waveguides terminated in an infinite plane conductor is formulated without using Green´s functions. The formulation is applicable for a source inside a waveguide as well as for an external source (e.g., a plane wave). Two principles, namely, the continuity of the tangential electric field and the conservation of complex power across the aperture of a waveguide completely determine the scattering mechanism at the aperture. In the proposed method, the normal modes of the free space instead of its dyadic Green´s functions are used to represent the external field. This describes free space as a uniform waveguide with its wall approaching infinity. This method is then applied to the problem of a coaxial waveguide radiating into semi-infinite space as an example.<>