Coaxial to Empty Substrate Integrated Waveguide Transition for Small Satellite Microwave Technology

Empty Substrate Integrated Waveguides (ESIW) integrate hollow 3D waveguide structures into printed circuit boards (PCBs), providing a compact, low profile, and low cost solution that can be easily connected to other circuits in the same PCB. Several transitions have been proposed to connect ESIW circuits to planar (microstrip or coplanar) lines. However, these transitions require complex manufacturing processes and are not directly compatible with standard measurement equipment, thus requiring additional transitions from the planar line to the coaxial probes of the network analyzer. This induces degradation in electrical performance due to the presence of multiple transitions. Therefore, the present work proposes two novel coaxial-to-ESIW transition designs based on magnetic coupling. The proposed structures offer a design process including an equivalent circuit model and a significantly simplified fabrication, relying solely on basic cutting and metallization processes. Both transitions achieve measured insertion losses of 1 dB and 0.7 dB, respectively, while also reaching measured return losses of 12.5 dB.