Frequency domain simulation of drive induced oscillation in a coupled cavity TWT

We present an approach to and an example of the simulation of drive induced oscillation (DIO) in a coupled cavity TWT based on a large signal, multi-frequency steady state formulation of the governing equations. A simulation code based on such a formulation can provide results in less time than a time domain approach, since it avoids having to integrate the governing equations through the initial transient startup of the amplifier. Two approaches to inhibiting DIO, namely (1) the introduction of a circuit velocity step in the output section, and (2) the use of lossy material in selected cavities in the output section are demonstrated using the large signal frequency domain code CHRISTINE-CC.