Advances in the field theory based CAD of MM-wave passive circuits

A rigorous field theory method is described for the accurate numerical design of a class of millimeter-wave passive circuits. The design theory is based on the mode-matching or spectral-domain method, respectively, for a few adequately chosen key building-block discontinuities together with the generalized modal scattering matrix technique for cascaded structures. This technique allows the inclusion of both the higher-order mode interaction at all discontinuities involved and the finite dimensions of the obstacles (e.g. finite metallization thickness of metal inserts or irises). The efficiency of the method is demonstrated by the CAD (computer-aided design) of some typical examples of technical significance: an aperture coupled T-junction, manifold and septate E-plane multiplexers utilizing E-plane integrated metal-insert filters, a tunable E-plane integrated circuit filter, an evanescent-mode metal-finned waveguide filter, and a coplanar waveguide structure. The theory is verified by measured results