Large-Signal Multifrequency Simulation of Coupled-Cavity TWTs

We describe a steady-state large-signal model of coupled-cavity traveling-wave tubes in which the input and output signals are periodic functions of time that may be represented by Fourier series of finite length. The model includes both linear and nonlinear effects including circuit dispersion, reflections, intermodulation, and harmonic generation. The model uses a lumped element representation of the circuit and a 1-D disk model of the beam. Several favorable comparisons of model predictions with experimental measurements, including gain versus frequency and power transfer characteristics, are illustrated. The inclusion of nonlinear effects in this multifrequency model enables predictions of intermodulation products, as functions of the input power. An example of the computation of C3IM is illustrated.