Simulation of a W-band kW-power two-stage klystron oscillator

We demonstrate the results of theoretical analysis and numerical simulation of a two-stage multiple-cavity klystron oscillator. We develop the small-signal theory of the oscillator, which predicts start-oscillation current and oscillation frequency. Results of 1.5-D particle-in-cell simulation of the oscillator with different number of cavities are presented. The numerical results are in good agreement with the small-signal theory. Optimal parameters of oscillator are evaluated. The simulations predict over 1.3 kW output power with nearly 650 mA beam current.