Schwinger coupler for substrate integrated circuits and systems

In this paper, a Ka-band Schwinger coupler based on Substrate Integrated Waveguide (SIW) and using LEGO-like interconnected PCB building blocks is proposed for the first time. This reversed phased coupler is composed of two interconnected SIW printed circuit boards (PCBs) coupled through slots spaced by a quarter wavelength. For demonstration purposes a prototype is fabricated. The measured results are in good agreement with simulations. The demonstrated coupler operates from 30 to 38 GHz. A week coupling of 20 dB (±1 dB) is achieved with an isolation and return loss better than −25 dB. The proposed geometry represents one of the key components for future 3-dimensionnal System on Substrate (SoS). Finally, for system development and repair purposes, the demonstrated coupler is proposed for SIW circuit probing.