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.