The development of a high efficiency broadband klystron

The design and experimental results of a five-cavity amplifier are described. This tube operates at a mid-frequency of 425 megacycles; it has a peak output of 8 megawatts, a peak efficiency of 42 per cent, and a 12 per cent electronic bandwidth with the efficiency exceeding 35% over a 10.5 per cent bandwidth. The driver section of the tube has been designed on an analog computer. Small-signal space-charge-wave theory is modified in the last 2 drift stages by the introduction of kinematic large signal effects. The influence of the design parameters upon optimization of the gain-bandwidth product and phase linearity is studied. Unequal drift lengths and the distribution of cavities with various Q's in the passband are considered. Considering the transfer function in the complex frequency plane, it is realized that a multicavity klystron is to a very good approximation a minimum phase network. A consequent interrelation between the phase and amplitude responses exists which allows the optimization of one only with some sacrifice in the other.