Rectangular Waveguide to Coplanar Waveguide Transition for 110 to 170 GHz

In this work a structure is shown to transition from a rectangular waveguide, across a square coaxial section to interface an on-chip coplanar waveguide (CPW) pad in the frequency range of 110 to 170 GHz. The structure allows to transition without the use of a carrier substrate, reducing the total amount of interfaces for the terahertz (THz) transition. It allows close placement of the chip to the transition, reducing the impact of parasitic components. A back-to-back structure is simulated including an analysis of manufacturing variations. The proposed structure shows to be robust to manufacturing tolerances and covers the whole D-band. First manufacturing tests are conducted, indicating that low-loss straight waveguide sections can be achieved, based on measured surface roughness much lower than the skin depth.