Wideband mm-wave transition between a coupled microstrip line array and SIW for high-power generation MMICs

A compact wideband transition between an array of microstrip lines (MLs) and a single substrate integrated waveguide (SIW) is presented. The spatially distributed fundamental SIW mode is excited by an array of parallel and strongly coupled MLs. The proposed configuration is optimized by minimizing the 'active' reflection coefficient at each ML port. Signals are transferred with nearly uniform power distribution across the ML ports, which facilitate an effective utilization of power amplifiers once interconnected. Measured results of the proof-of-concept demonstrator are in good agreement with simulations. The proposed configuration is capable of generating more power per footprint size relative to a single microstrip-to-SIW transition while offering a 50% bandwidth. At the same time, the compactness of the ML-to-SIW transition makes it suitable for tight integration with monolithic microwave integrated circuits and applications in wideband array antennas.