Half-mode substrate integrated waveguide (HMSIW) double-slot coupler

Based on a newly proposed guided wave structure of half-mode substrate integrated waveguide (HMSIW), a narrow-wall double-slot 3 dB directional coupler is proposed, which keeps the advantages of an SIW coupler but with a reduction of nearly one-half in size and better isolation. Simulated results are consistent with the measured data.