Mixed-Modes Conversion Method for Dual-Mode Relativistic Backward-Wave Oscillators

In this letter, a dual-cavity TM
₀₁
and TM
₀₂
mixed modes to TM
₀₁
mode converter is proposed for a dual-mode relativistic backward-wave oscillator (RBWO) application. This converter is more compact than the conventional converters and the TM
₀₂
mode is cutoff in the output waveguide, which forces the purity of the output TM
₀₁
mode to 100%. Especially, the converter is adjustable, and by simply replacing the waveguides in it, the converter can be well-matched to different proportional mixed modes. Electromagnetic simulation results show that the conversion efficiency of the converter is higher than 99%. The converter is validated in the high-power microwave (HPM) generation experiment of the dual-mode RBWO and a conversion efficiency of 98% is realized. A pure TM
₀₁
microwave with power of 4.6 GW and pulse duration of 42 ns at 10 GHz was obtained.