Hybrid full-wave analysis of stepped horn antennas with waveguides of arbitrary cross-sections

We introduce a new hybrid method for the complete full-wave analysis of stepped horn antennas with waveguides of arbitrary crosssections. The method couples an hybrid Mode Matching (MM)/ Two-dimensional-FiniteElement- Method (FEM2D) for the analysis of the internal part, i.e. for the waveguides step discontinuities from the horn input up to its aperture, to the Generalised- Multipole-Technique (GMT) for the analysis of the horn antennas external part. Since multipoles generates spherical waves, their use is particularly convenient to model radiation effects. The hybridization of the three methods (GMT, MM and FEM2D) allows us to take into account the real external shape of the antenna (by GMT) and to accurately and efficiently analyse the inner part of the antenna (by MM/FEM2D), without limitations on the shape of the waveguide cross-sections. Numerical examples validate the proposed a p proach.