The small signal theory assistant analysis of negative-positive phase velocity tapering

The fundamental method of the design of an ultra-broadband helix traveling wave tube (TWT) with two-section output circuit was analyzed using Pierce small signal theory, and shaped a special helix pitch profile with reduced phase-velocity followed by a positive phase-velocity taper. The slow wave structure with semi-metallic rods, which has good thermal dissipation capability and gives negative dispersion characteristics, was used to reduce the second harmonic content of a wide-band TWT in this paper.