Full Ka-band right-angle transition from substrate integrated waveguide to air-filled rectangular waveguide

A full Ka-band right-angle transition from a substrate integrated waveguide (SIW) to an air-filled rectangular waveguide is proposed. A two-step ridged waveguide and the SIW with an etched slot are jointly designed to obtain a better electric field and impedance matching between the SIW and the air-filled rectangular waveguide. To verify the method, a back-to-back transition prototype at Ka-band is designed, fabricated and measured. The measured results show that the insertion loss of a single transition is <;0.55 dB over the entire Ka-band from 26.5 to 40 GHz. Moreover, the 15 dB fractional bandwidth is increased from 25.7 to 40.9% compared with conventional right-angle SIW-to-waveguide transition. This broadband transition can be a good candidate for broadband millimetre-wave applications.