Multilayer Half-Mode Substrate Integrated Waveguide Wideband Coupler with High Selectivity

A novel 3dB wideband coupler with enhanced selectivity has been proposed and developed in multilayer HMSIW topology. Periodic ginkgo leaf slots (GLS) are etched on top layer of HMSIW to realize a pass band combining with high-pass characteristics of HMSIW. The novel GLS cells have stop-band characteristics aiming to improve the frequency selectivity and extend the upper stop-band. Moreover, the roll-off at the upper side is very sharper. A continuous coupling slot is etched in the conductor layer at the broadwall of HMSIW. Coupling takes place through the long, offset slot, which features a flexible design providing a wide coupling dynamic range with wideband characteristics. Detailed design process is introduced to synthesize a wideband filtering HMSIW coupler with better stop-band rejection. The novel coupler is showing a 34.9% coupling bandwidth at 8.87 GHz with good isolation, reflection and out-of-band rejection performances. Its stop band is from 13.8 to 17.6GHz with the rejection more than 40dB. Good agreement is obtained between the simulated and measured results of the proposed structure.