Analysis Method of Circular Waveguide TM01 Mode Converter on the Basis of Microwave Network

To accurately measure the performance of overmoded devices used in high-power microwave systems, a novel structure that effectively converts the TE 10 mode in a rectangular waveguide to a high-purity TM 01 mode in a circular waveguide is proposed. The scattering matrix technique was used to study the mode converter along with the microwave network analysis method, obtaining some generalizations of the input port reflection and conversion efficiency which were verified by the numerical full-wave simulation. Based on the theoretical analysis, an X-band TM 01 mode generator is designed and measured. Low-power tests show that, when the length of the tuner increases from 5.7 to 11.7 mm, a wide frequency tuning range of ∼500 MHz is obtained with a conversion efficiency of ∼99%. Measured results and the theoretical analysis are in good agreement