Analysis and Design of Broadband Ridge-Gap-Waveguide Tight and Loose Hybrid Couplers

A wideband broad-wall directional coupler is designed using the ridge-gap-waveguide (RGW) technology operating on the quasi-TEM mode. Large coupling apertures are used between two mirrored RGWs. Several coupling levels are achieved according to the number of apertures used and the ridge height in the two RGWs. Furthermore, a design procedure to obtain the desired coupling levels is introduced. Simulations and measurements show that tight-to-loose coupling levels (3-33 dB) can be achieved with the same coupler configuration, but with different parameters within +/- 1-dB coupling variations. The couplers achieve better than I5-dB return loss and better than 20-dB isolation within a 40% bandwidth with +/- 1 dB and e2 degrees of magnitude and phase errors, respectively.