Equivalent-circuit model of vircators with step circular waveguides (II)

Summary form only given. It has been shown, both experimentally and via computer simulation, that high-power microwaves can be generated from vircators with an abrupt discontinuity in circular waveguides. In the first part of this work, a rigorous equivalent-circuit model was established to determine the empty cavity oscillation modes (the front section of the waveguide acts as an open cavity), i.e., the Q factors, resonance frequencies, and field distributions in such vircators. In this presentation, the model is elaborated further to investigate the excitation of electromagnetic fields by virtual cathode oscillation in a step circular waveguide. We simplify the problem by approximating virtual cathode as a two-dimensional array of synchronized oscillating charged rings with each ring charge given from our two-dimensional particle-in-cell simulation results.