Rigorous hybrid MM/FE/MoM analysis of longitudinally corrugated horns

A hybrid mode-matching/finite-element/method-of-moment (MM/FE/MoM) technique is presented for the rigorous analysis of longitudinally corrugated horns. The horn taper is described by the mode-matching method where the cross-section eigenvalue problem is solved by a two-dimensional (2D) finite-element technique. For the exterior horn surface including the radiating aperture of arbitrary shape, the application of the Kirchhoff-Huygens principle yields an expression for the modal admittance matrix based on the electric field integral equation (EFIE). The equations are solved numerically by the method of moments. The eigenvectors of the last waveguide taper section and Rao-Wilton-Glisson (RWG) functions for triangular patches are utilized as basis-functions for the magnetic or electric surface current densities, respectively. The reported hybrid procedure combines the efficiency of the MM method with the flexibility of the FE and MoM techniques. The accuracy and efficiency of the technique are verified by reference measurements; its flexibility is demonstrated with a longitudinally corrugated horn example.