SMALL-SIGNAL THEORY OF A RIDGE-LOADED RING-PLANE TRAVELING-WAVE TUBE

The travelling-wave tube is an important high-power microwave amplifie r. The ridge-loaded ring-plane slow-wave structure can provide high ou tput power in a relatively broader bandwidth. Starting from the beam-p resent wave equation, the dispersion relation for the interaction betw een the electron beam and the symmetrical mode propagating in this slo w-wave circuit is obtained in this paper by means of the variational m ethod. Making use of the Newton downhill method the numerical results of small-signal gain and phase velocity are given. The influences of t he radius and current of the electron beam, the acceleration voltage a nd the geometrical dimension of the slow-wave structure on the small-s ignal gain and phase velocity are discussed. The instantaneous operati ng bandwidth can be estimated from the diagrams of the relation betwee n the gain and the frequency. This paper provides a theoretical basis for designing the ridge loaded ring-plane travelling-wave tube.