A hybrid type traveling-wave tube for high-power pulsed amplification

A hybrid-type traveling-wave tube suitable for high gain amplification at pulsed high-power levels is described. The device utilizes a filter-type loaded waveguide slow-wave circuit, with interaction below the propagating range of the circuit. This gives rise to a broad-band inductive-wall type of amplification with high gain per unit length. The particular structure outlined employs a spatial-harmonic traveling-wave circuit to couple the energy to the input and to extract power at the output. The main interaction circuit is separated from the input and output section by short ceramic terminations. With proper design, performance at good efficiencies is obtained over a 10 per cent bandwidth to date. A special feature of the device is the possibility of adjusting the gain variation with frequency to suit the designer. This comes about from the fact that the gain per unit length decreases with frequency in the coupling sections, and increases with frequency in the center (nonpropagating) section. By proper selection of the relative lengths of the two circuits, it is possible to obtain either flat gain or peak gain at either end of the frequency range. The efficiency does not appear to be affected by the center section and is limited by the characteristics of the output section only. With the present configuration, it was possible to obtain both good stability and reasonable efficiency simultaneously.