A Compact Wideband High-Power Microwave Circular Waveguide TM01–TE11 Mode Converter

A compact wideband high-power microwave (HPM) circular waveguide (CWG) TM $_{\text{01}}$ –TE $_{\text{11}}$ mode converter consisting of a CWG and a stepped septum is proposed. The septum with a rectangular groove and chamfers is arranged in a step shape, and then, a rectangular ridge is attached to the upper edge of the first step. Consequently, a wide conversion bandwidth and high conversion efficiency with TE $_{\text{11X}}$ mode transmission capability are obtained. The prototypes at an operating frequency of 8.4 GHz are fabricated and measured for verification. Results show that the bandwidth is larger than 13% for conversion efficiency higher than 90% from 8.05 to 9.14 GHz. In the band, the measured maximum TM $_{\text{01}}$ –TE $_{\text{11Y}}$ conversion efficiency is 99.7% and TE $_{\mathbf{11X}}$ mode transmission efficiency is more than 98.1%. Moreover, the power capacity exceeds 986 MW for breakdown field strength of 1 MV/cm. Therefore, the design has a good application prospect in HPM systems.