Additively Fabricated Air-Filled Waveguide Integrated With Printed Circuit Board Using a Through-Patch Transition

The hybrid integration of an additively fabricated air-filled waveguide (WG) with a printed circuit board (PCB) is presented. An arrangement is proposed where different waveguiding structures share the same common metal plane on PCB. Such an approach allows combining the low-loss and high- $Q$ properties of an air-filled waveguide, active circuit realization of the strip transmission line, and 3-D capabilities of additive manufacturing. A broadband transition is developed employing a through-patch coupling interface from a microstrip (MS) line to a waveguide. The concept was experimentally validated with exemplary transitions operating within $X$ -band and $K$ -band, featuring a measured bandwidth of $f_{h}/f_{l}~ \approx ~1.4$ and average per-transition loss including connecting lines of ~1.2 and ~1.9 dB, respectively.