Cold and Hot Matching of Coupled-Cavity Traveling-Wave Tubes

The matching condition for coupled-cavity travelingwave tubes is derived from an eigenvalue formulation. The slowwave structure is modeled by a simple equivalent circuit, and cold operation, i.e. without electron beam, is assumed. Several case studies of simple input and output matching circuits are presented. A dispersion analysis both without and with beam coupling is performed. It reveals the strong influence of the beam. Finally, the input reflection is exemplarily simulated in the presence of electron beams of different intensity (hot match). Beam coupling is shown to substantially alter the matching condition. This effect has to be considered when designing traveling-wave tubes based on cold data.