Influence of variations in the phase velocity and coupling impedance under the absorbing layer on the output characteristics of a wideband traveling-wave tube

Abstract

The electrodynamic parameters (coupling impedance, slowing factor, and damping factor) of a wideband traveling-wave tube (TWT) are calculated as functions of the surface resistance of the absorbing layer and of the frequency. The data obtained are approximated by quadratic polynomials within a wide range of values of the parameters, and a PC program is developed for computing the coupling impedance and slowing factor in the absorbing layer as functions of the longitudinal distribution of the damping factor and of frequency. The effect of these dependences on the output and statistical characteristics of a wideband TWT is analyzed. It is shown that the maximum effect is produced at the long-wavelength edge of the operating frequency range.