Design of a 16GHz TE11-HE11 mode converter in smooth-walled circular waveguide

The traditional TE₁₁-HE₁₁ mode conversion is usually achieved in a circumferentially corrugated waveguide with varying slot depth, which is easy to bring about microwave breakdown due to the machining burrs at the high frequency. In order to avoid this defect, the smooth-walled structure with a gradual change of the radius is given in this paper. Based on the mode coupling theory, a 16 GHz TE₁₁-HE₁₁ mode converter constituted by parabola-profile and sin-profile has been designed by numerical calculation, it also has been testified by electromagnetic simulation software. The simulation results are consistent with the numerical calculation results. The bandwidth of the designed mode converter is over 1.8 GHz, and the relative bandwidth is about 11%, the conversion efficiency at 16 GHz could reach 99.21%.