A broadband waveguide-to-50 Ω-microstriptransition with low-loss

Abstract

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, some of these transitions currently feature a rather narrow bandwidth, especially when the substrate is inserted transversal to the propagation direction of the waveguide. Here we present a new design that overcomes this problem. The transisition 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% and, moreover, can be scaled to other frequencies keeping good electrical characteristics. 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%.