Abstract:
Background Terahertz waves are widely utilized in radar, communications, and electronic warfare due to their unique properties, making terahertz radiation sources a critical research focus. As one of the primary terahertz sources, the backward wave oscillator (BWO) is a vacuum electronic device based on the interaction between the electron beam and the slow-wave structure (SWS). As the core component, the SWS significantly influences BWO performance. Recent studies have proposed various terahertz SWS designs, however, high losses in the terahertz band and low interaction impedance of existing SWSs remain key limiting factors for terahertz vacuum electronic devices.
Purpose This study aims to address these challenges by proposing a trapezoidal double ridge waveguide (TRWG) SWS, with the goal of enhancing interaction impedance to improve BWO output power.
Methods The electric field distributions of the TRWG, sinusoidal double-ridge waveguide (SRWG), and flat-roofed SRWG were compared. Both on-axis and average interaction impedance were evaluated at the identical normalized phase velocities. The TRWG geometry was optimized through simulation, and input/output structures were designed. Performance comparisons were conducted using particle-in-cell (PIC) simulations.
Results Simulation results indicate that in the frequency range of 320 to 360 GHz, the average interaction impedance of the TRWG is 78.33%−86.97% higher than that of the SRWG and at least 46.65% higher than that of the flat-roofed SRWG. Under the same operating conditions and within the same frequency range, the output power of the TRWG BWO in the 340 GHz band reaches 5.55−8.03 W, representing an increase of 26.97% to 73.44% compared to the SRWG BWO and an enhancement of 33.65%−52.47% over the flat-roofed SRWG BWO. After optimizing the tube length for all three BWOs, the TRWG BWO is at least 16.5% shorter than the other two structures.
Conclusions The TRWG SWS exhibits superior interaction impedance and output power compared to the other designs, offering a promising solution for high-performance terahertz BWOs.
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