GB564858A - Electron discharge apparatus for generating electromagnetic waves - Google Patents

Abstract

564,858. Sound transmitting apparatus. STANDARD TELEPHONES & CABLES, Ltd. May 2, 1941, No. 5724. Convention date, June 5, 1940. [Class 40 (iv)] [Also in Group XL] An electron discharge device for producing high frequency oscillations and communicating them to a waveguide 16, Fig. 1, comprises a source of a density-modulated electron stream including a first closed resonant chamber 12 in which the stream is velocity-modulated, a second closed resonant - chamber 20 forming part of the wave-guide and directly coupled, as by aperture 19, to the remainder thereof and having a gap 22 arranged in the path of the stream for extracting energy therefrom, and means such as the movable diaphragm or piston 23 for varying the volume of the second chamber to vary the resonant characteristics thereof in accordance with a modulating signal. A third chamber 14 may obstruct a portion of the energy of the stream and feed it back to the first chamber through the line 15 for self-excitation. The second chamber may be tuned to the same frequency as the first and third chambers or to a harmonic ; the piston 23 produces amplitude modulation when working on the side of the resonance curve. In a modification, resonators 12, 14 and 20 are coaxial cylinders in contact, the gaps being formed between tubes passing through the separating partitions. Coupling between resonators 12 and 14 is by a small hole in the partition between them. In a further modification, the beam passes transversely across two concentric cylinders, the inner one forming the second chamber 54, Fig. 4, and the outer being separated diametrically by system 63 into the first and third chambers 51, 53 respectively, coupled by gaps 62 near the inner wall. The functions of the second and third chambers are combined in the form shown in Fig. 5 into the resonator 65 which is coupled to the wave-guide 67 by aperture 68 and tapered portion 70. The volume of chambers 64, 65 is simultaneously varied by piston 66, so that frequency modulation is produced ; all three chambers of Fig. 2 may be simultaneously varied with a similar result. In a modification chambers 64, 65 are separate and their tuning pistons are coupled mechanically. If the electron beam is in the form of a ribbon, the gaps and all the dimensions of the resonators may be elongated in the direction of its width. The couplings apertures 19, 68 are sealed by glass or mica and may be followed by an iris diaphragm to enable the coupling to be adjusted.