Design of a Ku/Ka-Band Oversized Waveguide Bend for High-Power Transmission Line

A Ku / Ka -band oversized waveguide bend, transmitting the power of TE 01 mode at Ka -band and TE 11 mode at Ku -band, is designed for the high-power transmission line. To suppress the generation of parasitic modes, a waveguide bend based on the elliptical waveguide is used to minimize the coupling capacity between the operating modes and the undesired modes. The mode coupling rules inside the elliptical waveguide bend are investigated. The optimized parameters, including the orientation of bend plane, the bend radius, and the eccentricity are chosen according to the analysis results. The calculation results show that the transmission efficiency of the TE 01 mode is over 95% from 26 to 32 GHz, while the transmission efficiency of the TE 11 mode is over 98.5% from 10 to 20 GHz. To validate the design, a prototype is fabricated and measured. Compared with the calculated results, the measured transmission efficiency has a 4% and 5%–6% drop in the Ka -band and Ku -band due to ohmic loss. The high output mode purity of the waveguide bend is verified by the near-field measurements.