Modeling of practical multi-octave-band helical slow-wave structures of a traveling-wave tube for interaction impedance

A theoretical model is developed for evaluating the interaction impedance of practical helical slow-wave structures which are anisotropically and/or inhomogeneously loaded specially for multioctave bandwidths. The discrete supports have been azimuthally smoothed out into a number of dielectric tubes of different permittivity values, while the metal vanes have been modeled by an axially conducting cylinder suitably located in the structure.<>