Research on a 220-GHz modified staggered double corrugated waveguide backward wave oscillator

The output power of a backward wave oscillator (BWO) is limited by the low interaction impedance of a slow wave structure (SWS) when the frequency is in the THz band. A BWO based on modified staggered double corrugated waveguide (MSDCW) SWS is researched as a high-power source operating at THz band to break through the coupling impedance limitation in this paper. The MSDCW-SWS designed for BWO with wide electronic tunable band is optimized by numerical Eigenmode simulation to obtain higher coupling impedance. The simulation results show that the coupling impedance of MSDCW-SWS at 211.5 GHz is 42% higher than that of the original staggered double corrugated waveguide (SDCW) SWS when the dispersion conditions are the same for both SWSs. The sheet beam MSDCW-BWO with a broadband output structure is designed to operate under voltage between 23 and 49 kV and an electron beam current of 160 mA. The 3-D interaction simulation results reveal that more than 80.6 W of average output power can be produced from 210 to 238 GHz and the highest electron efficiency of 2.5% can be obtained at 211.5 GHz. The MSDCW-BWO can be considered a promising high-power THz source.