GB688925A - Improvements in travelling wave apparatus - Google Patents

Abstract

688,925. Travelling-wave tubes; magnetron amplifiers. COMPAGNIE GENERALE DE TELEGRAPHIE SANS FIL. May 19, 1950 [June 2, 1949], No. 12606/50. Class 39(i) In travelling wave apparatus two beams of primary electrons are emitted from opposite ends of the tube respectively, simultaneously or alternately. In one form, Fig. 1, electron guns 3, 4, 5; 6, 7, 8 generate annular beam 1 passing outside helix 2 and cylindrical beam 9 passing inside helix 2 in the opposite direction. The ends of the helix are coupled by dipoles 10, 11 to waveguides 12, 13 and a coil 14 focuses the beams. In one method of operation a signal is introduced by guide 12 and is amplified by beam 1 in the usual manner, the amplified output being taken off by guide 13. The dipole 11 and guide 13 are not perfectly matched so there is a reflected wave which is amplified by beam 9; dipole 10 and guide 12 are also not perfectly matched so that there is a further reflection in the direction of beam 1. By varying the potential or emissivity of cathode 6 and by adjusting the phase by known means the magnitude of the multiply reflected wave may be such as to reinforce the forward wave to a desired degree. In another method of operation for example in telephone line circuits, the tube will amplify in either direction or in both directions simultaneously; when amplifying in one specific direction the input and output guides are each provided with switching means to prevent simultaneous entry of two input waves travelling in opposite directions, or alternatively the reverse beam may be suppressed by impulses, synchronised with switching means, applied to the appropriate wehnelt electrode. In another embodiment, Fig. 2a, the device operates with crossed electric and magnetic fields. The helix 2 is flat, and electrodes 22, 23 negatively biased with reference to the helix set up the transverse electric fields for the respective beams which pass outside the helix on opposite sides thereof; the magnetic field is perpendicular to the plane of the paper. The input and output are led in and taken off by coaxial lines, Fig. 2b (not shown); the helix 2 may be replaced by a wire of sinuous form. The invention is also applicable to tubes of circular form. Specifications 663,728 and 677,536 are referred to.