Design and Optimization of a Broadband Waveguide-to-50 Ω-Microstrip Transition for Q-Band Applications with Low-Loss and Easy Scalability.

The increment in the demand for high-frequency monolithic integrated circuits has driven the development of waveguide-to-microstrip transition that allow their characterization and integration with waveguide components. Unfortunately, when return losses are taken into account, these transitions feature a rather narrow bandwidth, especially when the substrate is inserted transversal to the propagation direction of the waveguide. Here, we present a new scalable design that overcomes this problem. The transition was originally designed for a bandwidth of 33.5–60 GHz (extended V-band) with the simulation results showing reflections below − 19.5 dB in a fractional bandwidth of 55%. To validate the design, we show the scaling, construction, and measurement in an extended Q-band (27–50 GHz) with the additional advantage of having a standard impedance of 50 Ω. The most novel feature is a staggered air cavity for the microstrip and planar probe, which generates return losses better than 20 dB in a fractional bandwidth of 53%. [ABSTRACT FROM AUTHOR]