A Broadband Circular TE₀₁ Mode Converter Using Highly Deformed Circular Waveguide

A method for broadening the operating bandwidth of circular TE01 mode converter is proposed by using highly deformed circular waveguide (CW). The influence of deformation on the field patterns and the mode spectrum is investigated, and the maximum mode spectral gap between the TE01 mode and the undesired modes is deduced. According to the analysis, a K-band circular TE01 mode converter using highly deformed CW is designed, fabricated, and measured. The results show that conversion efficiency of a single mode converter higher than 89.1%, the reflection better than −20 dB, and the mode purity exceeds 98.7% within a relative bandwidth of 40.35%. The angle-independent transmissions demonstrating high mode purity and the appearance of TE01 mode is confirmed by the near-field pattern measurement. The mode converter features broad bandwidth, high mode purity, and compactness, which can be applied to cold-test experiments of gyro-TWT components and the high-power transmission line devices.