Design of a rectangular slot coupling for effective transition between two layers of SIW

An effective transition using rectangular slot coupling between two layers of Substrate Integrated Waveguide (SIW) is designed at 10.0 GHz. The analysis of the slot design is obtained by separated into two different cases of parametric study. First, the position of rectangular slot coupling. Second, the size of the rectangular slot coupling. The effective transition for the multilayer coupling are assessed based on the performance of return loss and insertion loss from S-parameters result. In order to validate the rectangular slot coupling design transition behavior based on full-wave simulation result, a simple equivalent modelling circuit is implemented using parallel lumped elements. The scattering parameters of the lumped parallel LC elements are calculated and evaluated based on the insertion loss at two frequency points. Results observed between LC model, simulation and measured data shows similar return loss less than -10 dB and insertion loss close to 0 dB. An agreement is observed over 9.2 GHz - 10.2 GHz of the frequency range where the most transition of effective coupling occurred at 10.0 GHz.