Enhanced Robustness in Wideband Rectangular Waveguide-to-Substrate-Integrated-Waveguide Transition Using Dielectric Superstrate

A superstrate-based air-filled rectangular waveguide (RWG) to substrate-integrated waveguide (SIW) transition covering the entire D-band <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(110 \text{GHz}-170 \text{GHz})$</tex> is presented, with a specific focus on the robustness of the topology against fabrication tolerances. The transition topology relies on a resonant slot and an aperture-coupled resonant patch, co-optimized with a dielectric-loading superstrate to ensure full D-band operation. Particularly, the effectiveness and robustness of this superstrate-based approach is analyzed and compared to alternative strategies. Additionally, the resilience of the proposed component against the strict design tolerances originating from its implementation in a standard Any-Layer High Density Interconnect Printed Circuit Board manufacturing process is analyzed. Measurements of multiple RWG-to-SIW transition prototypes demonstrate a fractional bandwidth of 46 %, effectively covering the entire D-band, while ensuring a low insertion loss of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.95 \pm 0.15 ~\text{dB}$</tex>, proving the proposed transition a reliable component for D-band RWG-to-PCB interfacing.