Scattering matrix subtraction technique for mode-matching analysis of substrate integrated waveguide junctions

A scattering matrix subtraction method is employed within the mode-matching technique (MMT) to model right-angle substrate integrated waveguide (SIW) junctions. The advantage of this approach lies in the fact that generalized scattering matrices of inline SIW waveguide circuits, including simple bi- and trifurcations are computed first. In a second step, the scattering matrices of regular waveguide corners are subtracted to yield the overall scattering matrices of right-angle SIW junctions. The method is demonstrated for a SIW corner with straight forward extension to T-junctions and cross junctions. Examples of a SIW corner filter, a SIW T-junction diplexer, a SIW cruciform hybrid and a SIW crossover demonstrate the validity of this technique.