HIGH-POWER TRANSIT-TIME OSCILLATORS - ONSET OF OSCILLATION AND SATURATION

A simple circuit model is used to investigate the transit-time oscilla tor (TTO) driven by a high-current diode. A novel condition for the on set of oscillation is derived in terms of the diode impedance. It is s hown that a low impedance is required for the production of high-power microwaves in a TTO. The initial growth is calculated, and the satura tion level is numerically computed using the one-dimensional model. Th ese one-dimensional (1-D) results are in excellent agreement with a fu ll scale two-dimensional Particle-in-Cell simulation. The success of t he much simpler 1-D model allows a close examination of the roles play ed by the convection current and by the displacement current, as well as the modification in the transit time due to the intense space charg e within the gap. (C) 1997 American Institute of Physics.