A Novel In-Line ESICL-to-ESIW Transition for High-Performance Empty Substrate Integrated Microwave Systems

This letter introduces a novel transition from empty substrate integrated coaxial line (ESICL) to empty substrate integrated waveguide (ESIW). Using a standard planar manufacturing process, this transition enables the development of a complete microwave system integrating various technologies. The design procedure is outlined, and two transitions from ESICL to ESIW for the <tex-math notation="LaTeX">$Ku$ </tex-math> - and <tex-math notation="LaTeX">K </tex-math> -bands show simulated return loss better 30 dB in the entire frequency ranges. To validate feasibility, a back-to-back ESIW–ESICL–ESIW transition is fabricated and measured, yielding return losses higher than 19 dB and insertion losses lower than 0.45 dB.