An approximate method to predict the characteristics of SIW-based directional coupler

In this paper, an easy-to-used method to predict the characteristics of SIW-based directional couplers is given. The simplified ray tracing method is presented and Floquet theorem is used to deduce the criterion of via spacing for the coupling window. Numerical results show that this method can rapidly and correctly predict the characteristics of multi-way directional couplers or power dividers based on the substrate integrated waveguide (SIW) technology. A SIW-based multi-way directional coupler is designed and measured as an example.