Design and simulation of high bandwidth compact folded waveguide slow wave structure for 0.65 THz traveling wave tube

This paper presents the design and simulation of a compact Folded Waveguide Slow-wave Structure for a 0.65 THz traveling-wave tube aimed at achieving a balance between bandwidth, output power, and fabrication-oriented structural simplicity. The proposed structure is analytically modeled to evaluate dispersion characteristics, phase velocity, and interaction impedance – ensuring efficient beam–wave synchronization. The design is optimized to obtain a relatively flat dispersion profile, enabling broadband operation. Cold-simulation analysis demonstrates excellent impedance matching with low reflection and minimal insertion loss. Particle-in-cell simulations are performed to investigate beam–wave interaction, yielding a maximum output power of 5.36 W and a peak saturated gain of 29.51 dB at 650 GHz. The −3 dB bandwidth is found to be 14 GHz, which closely agrees with the analytically predicted bandwidth of 16 GHz. The results validate the effectiveness of the proposed structure for high-frequency, moderate-power, broadband THz applications.