Large signal analysis of ring-bar slow-wave structures for a Ku-band traveling-wave tube

This work deals with an investigation of possibilities of using ring-bar slow-wave structures in medium-high power traveling-wave tubes in the Ku-band (13.75-14.50 GHz). Ring-bar SWSs are often used in high (pulsed) power TWTs and narrow band purposes. Its main advantages over the single helix are the higher interaction impedance (roughly twice) and the good rejection factor to the backward mode. The main drawback of this kind of SWS is a more dispersive phase-velocity profile that limits its bandwidth. The investigation here verified that this slow-wave structure, under some dispersion profile linearization techniques, can result in an interaction circuit with satisfactory gain profile over the Ku-band. An encouraging output power level around 60 dBm was theoretically achieved with variation of a few more than 0.5 dBm. The large signal analysis (hot model) was performed by an in house large signal lagrangian code under development and the cold tests with a 3D eigensolver.