Full D‐Band Superstrate‐Enhanced Transition for Rectangular Waveguide‐to‐PCB Interfacing

ABSTRACT A transition from air‐filled rectangular waveguide (RWG) to substrate‐integrated waveguide (SIW) is proposed that covers the entire D‐band (110–170 GHz). Broadband operation is obtained by leveraging a resonant slot and an aperture‐coupled patch antenna‐in‐waveguide, while co‐optimisation with a dielectric‐loading superstrate matches both resonances to the RWG and ensures full D‐band operation. Special attention is devoted to the stringent design restrictions that originate from its implementation in a standard any‐layer high density interconnect printed circuit board manufacturing process at D‐band frequencies, omitting inductive via posts, to maximise the robustness of the design against fabrication tolerances. Measurements of the RWG‐to‐SIW transition demonstrate a fractional bandwidth of 46%, effectively covering the entire D‐band, while ensuring a low insertion loss of 0.95 0.15 dB.