Design of a TE01-Mode Waveguide Bend Based on an Elliptical Waveguide Structure

A Ka-band broadband TE
₀₁
-mode overmoded waveguide bend based on an elliptical waveguide structure is proposed for high-power transmission line in this paper. To investigate the mode conversion inside the waveguide bend, the mode coupling coefficients of elliptical waveguide bend are theoretically deduced. The influence of the cross section on the power-handling capacity and the transmission efficiency is studied. Calculation and simulation results present that the proposed overmoded waveguide bend has a propagation bandwidth of 7 GHz (relative bandwidth of 21%) with an efficiency over 95%. A prototype is fabricated and measured. The average transmission efficiency is over 93% in the range of 29–36 GHz according to the S-parameter measurement. The results of near-field test demonstrated that a TE
₀₁
mode with high purity is obtained at the output port of waveguide bend. The high-power performance is investigated by connecting it with a Gyrotron traveling wave tube, and the waveguide bend works stable under a maximum output power of 150 kW. The measurement results demonstrate that a novel approach is proposed successfully for the design of high-power waveguide bend.