Modal Analysis of Substrate Integrated Waveguides With Rectangular Via-Holes Using Cavity and Multilayer Green´s Functions

The substrate integrated waveguide (SIW) comprising rectangular via-holes is herein treated by a rigorous full-wave modal analysis using the moment method entailing Green´s functions for rectangular cavities and planar multilayer structures in the spectral domain. Modal dispersion graphs generated by this solution approach are compared with those obtained by an independent commercial full-wave solver. The ability of the modal solution in treating SIW junctions and discontinuities is demonstrated by the treatment of an interconnection between a conventional waveguide and a SIW using the mode-matching technique. Inhomogeneities within SIWs can also be accommodated by the technique, as showcased by a specific example of the so-called hard sidewalled SIW. Three avenues of losses, namely, dielectric, side-leakage, and conductor losses, are also investigated, thereby elucidating a tradeoff between the latter two.