Wideband transitions from Substrate-Integrated Waveguide to Coupled Microstrip lines and their applications to power dividers

Three wideband transitions from Substrate-Integrated Waveguide (SIW) to Coupled Microstrip (CMS) lines are presented. It is demonstrated that a transition from the fundamental SIW mode to the even quasi-TEM mode of the CMS is straightforward, whereas dominant coupling to the odd mode is only realizable by removing parts of the ground plane. Asymmetric transitions maintaining the ground plane excite a hybrid mode which includes both quasi-TEM modes of the CMS. For this hybrid mode, the excitation ratios between the even- and odd-mode components can be varied, and an unequal power divider is obtained. Performances of the individual transitions and power divider are verified by commercially available field solvers. Dimensional parameters are provided.