GB456301A - Improvements in or relating to thermionic amplifiers for electromagnetic waves - Google Patents

Abstract

456,301. Repeating- arrangements. STANDARD TELEPHONES & CABLES, Ltd., 63, Aldwych, London.-(Assignees of Potter, R. K.) Dec. 20, 1935, No. 35345. Convention date, Jan. 22. [Class 40 (iv)] [See also Group XL] A thermionic amplifier tube for electromagnetic waves comprises a heated cathode, a grid and an anode all of greater length than the longest wave length to be amplified, and all arranged with their lengths lying in the direction of propagation of the waves to be amplified, an input circuit being connected at one end of the tube to the cathode and one of the other electrodes, and an output circuit at the other end of the tube to a different pair of electrodes. In a communication system comprising such a tube the input and output circuits are concentric conductor pairs. In the form shown in Fig. 1, a cylindrical positive anode 13 and negative grid 15 are arranged concentrically around a filamentary cathode 18, the evacuated space being completed by glass end walls 14, 14<1>. The input circuit is a pair of concentric conductors 11, 12, the inner one being connected to the cathode and the outer one capacitatively coupled to the grid through condenser plates 16, 17. The output circuit 11<1>, 12<1> is capacitatively coupled to the grid and anode through condenser plates 16<1>, 19 and 28, 29 respectively, conical extensions 30, 31 being provided to maintain a uniform characteristic impedance. The far ends of the grid and anode are provided with correct terminating impedances comprising discs 27, 27<1> of resistance material mounted within condenser plates 26, 26<1> coupled to anode and grid respectively. As shown diagrammatically in Fig. 5, the incoming wave travels along the grid and is absorbed in impedance 27<1>. Each positive peak is accompanied by a stream of electrons which travels across to the anode and induces in it amplified waves, of which the one travelling to the right is built up, while that travelling to the left suffers interference and is finally absorbed in impedance 27. The amplified wave passes along the output conductors 11<1>, 121. In a modification, Fig. 6 (not shown), the tube is operated with the grid positive and the anode negative, the input wave being applied between anode and cathode, and an amplified wave being induced between grid and cathode.