Low-Insertion-Loss, High-Power Rectangular Waveguide-To-Coaxial Transition

A low-insertion-loss, high-power rectangular waveguide-to-coaxial transition is proposed in this letter. The proposed rectangular waveguide-to-coaxial transition is constructed by a rectangular-waveguide H-T junction and square coaxes. The H-plane T-junction is used to convert the input wave into two in-phase waves. After passing through three 90 degrees bends, the electric field vectors of the two in-phase waves are in opposite directions. Then they combine at the coaxial port. The TE10 mode in the rectangular waveguide is converted to the TEM mode in the coaxial line by the transition ridge. The power capacity of the transition is increased by the N-type connector. For verification, an X-band rectangular waveguide-to-coaxial transition has been designed, fabricated, and measured. The measured results show that the 20-dB fractional bandwidth is 22.4%. The insertion loss is no more than 0.1 dB. The transmission efficiency is 97.7%. And the power capacity can reach 65 kW.