Simulation studies on dispersion characteristics of coaxial terahertz slow wave structures

In this paper, the coaxial slow wave systems which are used in the terahertz traveling wave tube (TWT) are modeled and simulated by 3D electromagnetic simulation software. The electromagnetic field distribution of the slow wave structure is analyzed. The influence of the structure parameters on the dispersion characteristics is studied by modifying the structure parameters, such as the slot width, groove depth, ripple spacing, inner axis radius and so on. The coupling impedance of system is also calculated. It is found that the slot width and spacing have weak effect on the dispersion characteristics, and the phase velocity at same frequency decreases obviously with the increase of slot depth and inner axis radius. The operating frequency of proposed coaxial slow wave structure can cover 200~400 GHz, and the central operation frequency is about 0.3 THz.