A General Mode Matching Technique applied to Bandpass Radomes

Abstract

A new method based on the mode matching technique and the finite element method (FEM) is presented. The method can handle a general thick frequency selective structure (FSS), that consists of an arbitraryn umber of aperture layers and dielectric layers. An aperture layer consists of a conducting plate with a periodic arrayof apertures. The order and the thickness of the layers can be arbitrary. The aperture can have arbitrary cross-section, and these cross-sections can be changed stepwise. The apertures can also be filled with a dielectric material. The method for the bandpass radomes is based on general mode matching technique and cascade coupling. The fields outside the FSS and inside the dielectric layers are expanded in Floquet modes. Inside the aperture layers the fields are expanded in waveguide modes, which are calculated with FEM. Bya mode matching technique, a scattering matrix is calculated for every boundarysurface and a propagation matrix is calculated for everyla yer. These matrices are cascade coupled to form a scattering matrix for the complete FSS. The method has been verified bycomparison with other methods and measurements.