Efficient MLFMA analysis of coupled rectangular and circular apertures in a finite screen

A multilevel fast multipole algorithm (MLFMA) is introduced for the efficient analysis of coupled rectangular and circular apertures of different size within a finite conducting screen. The electric field integral equation (EFIE) is written in terms of mixed potential formulation. Aperture waveguide modal eigenvectors and Rao-Wilton-Glisson (RWG) functions for triangular patches are utilized as basis functions for the magnetic and electric surface current densities, respectively. For the resulting method-of-moments (MoM) solution, a MLFMA is formulated which includes the modal excitations of the coupled rectangular and circular apertures. This leads to significantly reduced computational complexity for these kinds of problems. The method is verified by available measurements and reference calculations.