GB773709A - Improvements in or relating to backward travelling wave oscillator tubes - Google Patents

Abstract

773,709. Travelling wave tubes; space charge wave tubes. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. March 25, 1955 [March 25, 1954], No. 8866/55. Class 39(1). In a backward wave oscillator a first electron beam interacts with the field of the delay line, and a second electron beam travels parallel to in the same direction as the first beam but with a lower velocity than that of the first beam ; the first beam interacts with the delay line to generate a backward wave while the two beams interact to give space charge wave amplification and the operating frequencies are so chosen that the. spade charge wave amplification-frequency characteristic is of opposite slope to that of the backward wave interaction of the first electron beam and the delay line so that the output power is maintained constant over a wide frequency range. The relative velocities of the beams are such as to allow such interaction between them as will produce a growing space charge wave. If beam 4, Fig. 2, is coupled to delay line 7 while beam 5 is not coupled to the delay line then the variation in output power over the electronic tuning band characteristic of the beam 4-delay line system is compensated by an opposite variation in power output with frequency characteristic of the space charge wave amplification system so the power output of the tube as a whole is maintained constant over the electronic tuning band. The velocity of beam 5 is kept constant. The delay line 7 is interdigitated and supports a spatial harmonic component of negative phase velocity for interaction with beam 4. Envelope 1, collector 6, delay line 7 and the anodes of the guns are grounded and an annular permanent magnet 14 focuses the beams. If in a modification, Fig. 4 (not shown) both beams are equally coupled to the delay line then the output frequency is intermediate the frequencies corresponding to the voltages of the two beams, i.e. f1 + f2. Operation of Fig. 4 is otherwise the same as in Fig. 2. Specification 699,893 is referred to.