Phase locking of a gyrotron in the hard excitation mode

In the theory of self-oscillating systems usually one distinguish two different kinds of self-excitation, namely soft and hard excitation. In the hard excitation mode a self-oscillation is sustained only for a sufficiently intensive initial perturbation, which amplitude exceeds a certain threshold, while a small perturbation decays. The phenomenon of hard excitation is natural for many electronic oscillators. In particular, in a gyrotron a maximal efficiency is often attained in the hard excitation regime. In recent years, the problem of phase locking of a gyrotron by an external driving signal has attracted a significant interest. This work is aimed on study of injection-locked operation of two models of a gyrotron in the hard excitation mode.