Millimeter-Wave Waveguide-to-Microstrip Inline Transition Using a Wedge-Waveguide Iris

Abstract

A novel waveguide-to-microstrip inline transition was proposed using a wedge-waveguide iris to form an ultra-compact U-bend waveguide. The wedge-waveguide iris not only functioned as a wide wall of the height-reduced waveguide for the <inline-formula> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula>-plane probe, but also played a critical role in impedance matching and parasitic resonance suppression. The working principle was investigated through theoretical analysis and full-wave simulation, and the relevant design processes for the transition were discussed. Moreover, two back-to-back transition prototypes, one working at the <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band and the other working at the WR4.3 band, were designed, fabricated, and measured. The back-to-back prototypes obtained an insertion loss of less than 0.8 and 1.2 dB, with a return loss better than 15 dB in the <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band and WR4.3 band, respectively. The measurement results were consistent with simulation results. A miniaturized 110-GHz tripler incorporating this transition for inline output was fabricated. A conversion efficiency of 2.5&#x0025;&#x2013;3.6&#x0025; was achieved in 90&#x2013;120 GHz at 100-mW driving power.