Development of a Ka-Band Circular TM₀₁ to Rectangular TE₁₀ Mode Converter

The output/input circuit is a core component in all high-power millimeter-wave (MMW) radiation sources, and its performance specifications and reliability directly impact upon the performance of the radiation source device. Central to achieving high power is the development of efficient mode converters. Here, we report on the development of a compact Ka -band circular TM01 to rectangular TE10 mode converter. The present mode converter adopts an all-metal waveguide structure and facilitates notable improvement in the system power capacity and is capable of realizing high-power propagation. The mode converter realizes effective mode conversion between high-order and fundamental modes, as well as allowing longitudinal and transverse transmission. Our simulation and empirical findings have shown mode purity ≥99.5% in the frequency range of 32.7–34.6 GHz, and the mode conversion efficiency is more than 96% at a center frequency of 32.9 GHz with a return loss ${S}_{{11}}$ of −19.3 dB. The bandwidth of the converter is 2.4 GHz with transmission coefficient ${S}_{{21}}\ge -{1}$ dB.