Characteristics of Micro-Fabricated Rectangular Ring-Bar Slow Wave Structure for THz Vacuum Electron Devices:A Simulation and Theoretical Study

The dispersion and coupling impedance, of the rectangular ring-bar slow wave structure (SWS) micro-fabricated on dielectric substrates of traveling-wave tube (TWT) for THz vacuum electron devices, were mathematically formulated with equivalent circuit model, theoretically analyzed, empirically simplified in quasi-TEM approximation and numerically simulated with software HFSS. The calculated and simulated results were in good agreement. The simulated results show that the dielectric material filled in the rectangular ring-bar SWS has a major impact. For example, the dielectric material significantly decreased the dispersion and phase velocity but considerably increased the bandwidth. In addition, the rectangular ring-bar slow-wave structure (SWS) was found to outperform the rectangular helix SWS because of higher gain and larger output power. We suggest that the simulated results may be of some technological interest in micro-fabrication of compact TWTs working in millimeter and sub-millimeter wave ranges.