Highly robust wideband rectangular waveguide-to-substrate-integrated-waveguide transition leveraging a dielectric superstrate

This work presents a comprehensive analysis of a superstrate-based air-filled rectangular waveguide (RWG) to substrate-integrated waveguide (SIW) transition that spans the entire D-band (110–170 GHz). The transition architecture exploits a resonant slot together with an aperture-coupled resonant patch, jointly optimized with a dielectric-loading superstrate. Its operation is examined in detail through an equivalent circuit model to analyze its key operating mechanisms. The robustness of the proposed superstrate-based concept is then further evaluated and compared with alternative topologies through full-wave electromagnetic simulations. Particular emphasis is placed on realizing the design within a standard Any-Layer High-Density Interconnect printed circuit board (PCB) process, by ensuring its tolerance to manufacturing variations. Measurements of multiple RWG-to-SIW transition prototypes show a 46% fractional bandwidth, covering the entire D-band, and a low insertion loss of 0.95 plus or minus ± ± 0.15 dB, confirming the significance of the proposed transition as a reliable component for D-band RWG-to-PCB interfacing.