A Wide-Band 0.34 THz Backward Wave Oscillator Based on T-shaped Staggered Double-Vane Interaction Structure

Terahertz backward wave oscillators, utilizing staggered double-vane interaction structures, are pivotal components in contemporary satellite communication systems, spectroscopy, and imaging. This study proposes an innovative T-shaped staggered double-vane interaction structure for a 0.34 THz sheet beam backward wave oscillator. The newly devised interaction vanes enhance the electric field distribution within the beam-wave interaction zones, concurrently increasing the interaction impedance of the structure. Through small and large signal analysis, the efficacy of the proposed design is validated and compared with a conventional staggered double-vane configuration. Operating under identical conditions of a 20 kV beam voltage and a 50 mA beam current, the novel T-shaped staggered double-vane interaction structure showcases an interaction impedance of 0.95 ohms at 0.34 THz, an output power of 10 W, and a -3dB bandwidth extending to approximately 60 GHz. By contrast, the conventional configuration records values of 0.68 ohms, 7.5 W output power, and a $40 \mathrm{GHz}-3 \mathrm{~dB}$ bandwidth, respectively. A comprehensive 3D model of the backward wave oscillator, incorporating emitter and waveguide ports, is proposed which facilitates analysis of transmission and reflection characteristics. Simulation results demonstrate a reflection coefficient $S_{11}$ significantly below -15 dB and a transmission coefficient $S_{21}$ well above -2 dB. All simulations are conducted in CST, employing copper with a conductivity of $2.2 \times 10^{7} \mathrm{~S} / \mathrm{m}$. The interaction structure comprises 100 uniform periods, including transition sections. The substantial bandwidth of the proposed interaction structure in terahertz backward wave oscillators underscores its versatility for spectroscopy, imaging, and communications applications.