Experimental investigation on millimeter-wave folded-waveguide TWT using linear electron beam

Summary form only given, as follows. Folded waveguide traveling wave tube (FWTWT) is one of the candidates for high power, broad-band and robust millimeterwave sources, because it has the advantages of simple structure compatible to planar precise-fabrication technologies, easy coupling and high thermal capacity due to all-metal structure. In contrast to general slow wave structures using periodic load such as stubs, disks and sinusoidal ripples, FWTWT has no periodic reactive load. The periodicity itself of the E-plane folded waveguide slows down the velocity of a TE-mode electromagnetic wave in the rectangular waveguide and generates space harmonics of virtual TM-mode along the beam propagation direction. Therefore, the dispersion relations of space harmonics can be easily estimated by simple transform of that of rectangular waveguide.