Circular coaxial orthogonal-mode-junction coupler and its application

A circular coaxial waveguide with four side-coupled rectangular waveguides is proposed as a multiband coupler for a wideband dielectric-cone-loaded feed horn. This structure is designed to separate multiple bands from the lower band of the feed horn with minimum impact on the highest band propagating in the inner circular waveguide that makes up the core of the coaxial waveguide. The proposed coaxial orthogonal-mode-junction (OMJ) coupler with associated matching irises and transition steps is analysed using boundary-contour mode-matching (BCMM) in conjunction with the mode-matching (MM) method. The results are verified using the finite-element method. The combination of BCMM and the MM method significantly speeds-up the design cycle of the proposed OMJ coupler so that computer optimisation of the structure is possible