Design procedure for hot-matched severs in folded-waveguide traveling-wave tubes

A design procedure for a hot-matched sever for folded-waveguide traveling-wave tubes (FW-TWTs) is proposed. To determine a starting point for a suitable load design, a realistic three-dimensional sever structure is developed using equivalent circuits and subsequent particle-free (cold) full-wave simulation. Additional wave impedance information, obtained by a small-signal eigenvalue analysis, is used to improve the termination for hot operation. The final full-wave optimization is then performed in the presence of the electron beam with only moderate computational effort. This procedure is applied to develop a sever structure for a given frequency point at Q-band. The simulated results support the approach.