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 −10dB and an insertion loss less than 1.2dB from 26.2GHz to 40GHz, which covered the whole Ka-band.