Forward-wave 0 dB directional coupler based on microstrip-ridge gap waveguide technology

In this paper, we propose a novel 0 dB forward-wave coupler realized in microstrip-ridge gap waveguide technology. The coupler is based on two microstrip-ridges coupled through an array of mushroom inclusions. A detailed design procedure is presented including the design of the hosting PMC structure, microstrip-ridge and the coupler. The proposed structure represents the first forward-wave coupler realized in gap waveguide technology. It is characterized by high coupling level of 0.3 dB at 13.54 GHz, and the 0.48 dB coupling variance over the bandwidth of 26%. Also, good performances in terms of the isolation and directivity have been achieved.