3D-Printed 3 dB Hybrid Coupler for D-Band Applications

In this work, an additively manufactured 3 dB hybrid coupler for the D-Band frequency range is presented. The plastic body is printed from UV-curable polymer resin with a conventional desktop DLP printer and subsequently functionalized by an electroless silver plating process. The slotted waveguide approach is used, in order to improve the metal coating and enable the implementation of complex waveguide structures. Measured isolation and matching range at -15 dB while the asymmetry in magnitude between coupling and through port remains below 0.8 dB over the frequency range from 115 to 154 GHz, yielding an operational relative bandwidth of almost 28 % and hence, suggesting general feasibility for directional coupling applications. Measured phase differences deviate from the desired 90° by 40° to 50° which is related to the overall tolerances with respect to absolute geometrical dimensions of conventional desktop DLP printers and required post processing.