GB730773A - Improvements in or relating to electric discharge devices - Google Patents

Abstract

730,773. Travelling-wave tubes; magnetron amplifiers. WESTERN ELECTRIC CO., Inc. March 21, 1952 [April 11, 1951], No. 7319/52. Class 39 (1). To reduce the effect of noise fluctuations in the electron stream of a travelling wave tube in which there is cumulative interaction between the electron stream and an electromagnetic wave to secure gain for the wave, the wave transmission circuit is continuous and includes a preliminary section 11 and a main section 13 in both of which interaction occurs, and an intermediate section 12 in which interaction is inhibited, but is so designed that the increasing wave component of the noise induced at the beginning of the preliminary section is attenuated in magnitude and shifted in phase so as to be equal in magnitude and opposite in phase at the beginning of the main section to the increasing wave component of the noise induced at that point, and thereby to secure cancellation of this component. The main section is of sufficient length to make the other components of the noise wave become unimportant. The input signal may be inserted at the beginning of the main section. The travelling-wave tube may be of the magnetron type, Fig. 3 (not shown). For inhibiting interaction between the electron stream and the wave in the intermediate section the wave velocity in this section may be changed, for instance with the wave transmission circuit in the form of a helix, by altering the pitch or radius of the helix, or by surrounding the helix by a dielectric cylinder. Alternatively the average velocity of the electron stream may be modified. A conducting cylinder 54, Fig. 4c, between the preliminary section 51 and the main section 53 of the helix is at a D.C. potential with respect to the helix. Another method is simply to displace the intermediate section 42, Fig. 4b, with respect to the preliminary and main sections 41, 43. These methods may be applied to a wave-guiding structure comprising a conductor having a series of lateral slots along the path of the electron stream. In Fig. 6a the spacing of the slots is altered, in Fig. 6b the slots are displaced, in Fig. 6c the slots are filled with dielectric, and in Fig. 6d the intermediate section 92 is at a D.C. potential with respect to the preliminary and main sections 91, 93. Specifications 652,155, 654,386 and 714,832 are referred to.