Analysis and Design of a Wideband Coaxial Transition to Metal and Printed Ridge Gap Waveguide

In this paper, a wideband coaxial to ridge gap transition is proposed and implemented. The transition has a compact size, wide bandwidth, and simple structure. It can be used to excite ridge gap waveguides implemented by the printed circuit board or computer numerical control (CNC) technologies. A similar circuit model for a coax-to-microstrip junction is proposed and used to establish a systematic design procedure for the proposed transition. Perfect electric conductor and perfect magnetic conductor (PMC) boundaries are used to make the procedure independent of the fabrication technology. The PMC is replaced by a bed of nails for ridge gap realized by CNC technology and mushroom-shaped structure in the case of PCB technology. The proposed transition based on the PCB technology is fabricated and measured. There is a good agreement between simulated and measured results which validates the proposed design. The transition has a 59.22% bandwidth with S
₁₁
<; -10 dB and S
₂₁
> -0.5 dB.