A comically coupled waveguide-to-coaxial line transition in a reduced-height waveguide for compact transceivers

A conically coupled waveguide-to-coaxial line transition in a rectangular waveguide whose height is very small compared with that of the standard Ku-band waveguide is designed and characterized. The input power to the reduced-height waveguide is coupled to the coaxial line through a metallic cone attached on the waveguide wall. The guiding property of EM waves in the reduced-height waveguide is found to be drastically different from that in the regular waveguide. The transition structures have been comprehensively analyzed using 3D EM simulators. The measured performance of the fabricated transition shows good agreement with the simulated results over the Ku-band frequencies, providing broad bandwidth of 5 GHz. The insertion loss of the transition is measured to be about 0.4 dB and the return loss is about 15 dB at 16 GHz. These transitions can be utilized for the construction of broadband compact-sized transceivers for the input coupling of closely spaced array antennas.