This paper presents a 3D-printed dielectric directional coupler for the sub-THz band from 140GHz to 220GHz. In contrast to conventional coupling approaches, a quasi-optical operating principle is implemented, which is based on the insertion of a thin dielectric boundary within a dielectric image guide. Due to an intended permittivity shift, the boundary layer acts as a wavesplitter for incident HE11 waves, whose partial reflections are selectively controllable via material or geometry parameters.
