A novel hybrid dispersion slow-wave circuit for 0.2 THz travelingwave tube

In recent years, travelling wave tubes (TWTs) have been commonly used in radar, space communications, and other applications due to their high power and wide bandwidth characteristics. The folded waveguide (FW) has relatively high interaction impedance and has become the preferred slow wave structure for high power TWTs. However, as the operating frequency increases to the terahertz band, the lower interaction impedance of the FW limits the performance of the TWT. To further enhance the interaction impedance of the FW, a groove-loaded FW is proposed. However, this structure has stability problems because of high order-mode oscillations. To suppress the high-order mode oscillations, a novel hybrid dispersion slow wave circuit for 0.2 THz TWT is proposed. Compared with the conventional slow-wave circuits, this hybrid dispersion slow-wave circuit does not require additional attenuators. For groove-loaded FW, the size of the groove significantly affects the dispersion of the slow wave structure (SWS). According to this characteristic, by optimizing the size of the groove, a relatively strong dispersion (SD) SWS and a relatively weak dispersion (WD) SWS are obtained, and the SD SWSs and the WD SWSs are connected alternately to form a hybrid dispersion slow wave circuit. The slow wave circuit not only achieves higher gain with shorter length but also effectively suppresses the oscillations without attenuators.