Miniaturized Hybrid Ring Coupler Using Electromagnetic Bandgap Loaded Ridge Substrate Integrated Waveguide

A novel compact Ridge Substrate Integrated Waveguide (RSIW)-based hybrid ring coupler is hereby presented. The size miniaturization is accomplished through a twofold approach. First, the RSIW is used to reduce the coupler waveguide transverse dimension. The RSIW of the hybrid ring is then loaded by Electromagnetic Bandgap (EBG) structures, etched in its non-ridged broadwall, exploiting their slow wave effect to reduce the longitudinal dimension. It is demonstrated that the use of EBG-loaded RSIW can lead to a size reduction of more than 48% and 91% with respect to the unloaded RSIW and conventional SIW hybrid ring couplers, respectively.