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.