Modulation Processes in Multi-cavity Klystron Amplifiers†

The input to output amplitude and phase modulation characteristics of multi-cavity klystron amplifiers are derived, subject to many simplifying assumptions. Ballistic electron bunching theory enables analytical description of the a.m. degeneration experimentally observed in saturated klystron amplifiers. The cases of two-cavity amplifiers, three-cavity synchronously tuned amplifiers and three-cavity amplifiers tuned for peak efficiency are considered in detail and graphs of the modulation conversion effects are plotted for parameters characteristic of a 2 kW, four-cavity klystron amplifier. It is shown that the synchronously tuned amplifier should have lower output a.m. but higher output a.m, than when tuned for peak efficiency.