Broadbanding studies of multimegawatt klystron amplifiers

The results of extensive experiments in the broad-banding of megawatt klystron amplifiers are presented. Four C-band tubes having 5, 6, 7, and 8 cavities, a 6-cavity L-band tube, and a 5-cavity X-band tube are discussed. It is shown that bandwidths of 10 per cent in L-band, 9 per cent in C-band, and 5 per cent in X-band can be achieved by proper stagger tuning of the driving cavities and use of a broadband output circuit. Examination of the relationship between gain and bandwidth indicates that the choice of design parameters becomes more critical as the number of cavities is increased. In the study of broadband tubes, it is convenient to consider the drive bandwidth and output circuit separately. The drive bandwidth is defined as the bandwidth obtainable from the drive section with essentially a constant-impedance output circuit, i.e., a tunable output cavity. The over-all bandwidth results from the combination of the response curves of the drive section and the output circuit. In practice it has been found that the tuning producing the flattest gain characteristic for the drive bandwidth must be modified in order to obtain the flattest over-all characteristic with broadband output circuit.