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

A compact wideband high-power microwave (HPM) circular waveguide (CWG) TM01–TE11 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 TE11X 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 TM01–TE11Y conversion efficiency is 99.7% and TE11X 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.