X-Band In-Line Coaxial-to-Groove Gap Waveguide Transition

A coaxial-to-groove gap waveguide transition is proposed for the first time, addressing the lack of similar designs in the state-of-the-art literature. An in-line configuration is adopted in case of stringent space requirements in groove gap waveguide systems. This device has no dielectric and makes use of a waveguide multi-step ridged section connected to the inner conductor of a coaxial line. Three versions are presented, covering progressively wider bandwidths depending on the number of employed steps. The three configurations achieve 20-dB return loss fractional bandwidths of 2.63%, 16.79%, and 38.08%, and 30-dB return loss fractional bandwidths of 0.84%, 10.63%, and 33.49%, with a simulated insertion loss always better than 0.05 dB when a realistic metal conductivity of 2 × 10 7 S/m is assumed. A tolerance analysis on the most critical geometrical parameters is provided to assess the mechanical feasibility, preserving a remarkable performance at X band.