Efficient boundary contour mode-matching method of H- and E-plane junctions by fast Fourier transform algorithm

An efficient boundary contour mode-matching method (BCMM) is applied to the analysis of H- and E-plane junctions with planar and circular boundaries. The proposed approach is based on the use of the fast Fourier transform (FFT) to improve an analytical BCMM method. The electromagnetic field inside the structure is expressed in terms of circular waves, whereas in the rectangular ports a modal expansion is used. Depending on the shape of the contour, the original field expansion is rewritten in plane waves or in other sets of circular waves, replacing the conventional numerical integrations by a new, more suitable procedure. Finally, the transformation between the different expansions is carried out by means of the FFT, increasing notably the efficiency of the method. The presented formulation is verified by comparing simulated results with those obtained by other numerical techniques