A forward narrow-wall double-slot 3 dB coupler based on hybrid HSIW/GCPW guided-wave structure

Based on a novel hybrid guided-wave structure of half-mode substrate integrated waveguide (HSIW) and ground coplanar waveguide (GCPW), a forward narrow-wall double-slot 3 dB coupler with the center operating frequency of 18 GHz is proposed. The narrow-wall double-slot coupling mechanism between TE10 mode of SIW and TEM mode of GCPW is studied and efficient coupling is achieved by using triangle-shaped slots. Such coupler takes the advantages of low profile, low insertion loss of HSIW and flexibility of GCPW. The coupler is fabricated and the measured results are in agreement with the simulated ones. A relative bandwidth over 20% is achieved with 0.5 dB amplitude imbalance excited at different ports.