Compact, broadband waveguide-to-microstrip transition using slotline antenna

This paper introduces a new waveguide-to-microstrip transition at Ka-band. The transition is composed of a slotline antenna and a slotline-to-microstrip transition. One of the main features of the new transition is that the uniplanar circuit is in line with the rectangular waveguide, so it is highly compatible with MIC technology and can be easily integrated with the waveguide. Furthermore, it has characteristics of compact size, broad bandwidth, and low fabrication loss. A demonstrate transition is designed and fabricated. The back-to-back combination was measured, and the tested results agreed well with the simulated results. The Ka-band transition has a 42% bandwidth with return loss better than -10 dB and an insertion loss less than 1.2 dB from 26.2 GHz to 40 GHz, which covered the whole Ka-band.