GB421652A - Improvements in and relating to oscillation generating arrangements including magnetrons - Google Patents

Abstract

421,652. Valve modulating circuits ; thermionic valves. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Electra House, Victoria Embankment, London, and LADNER, A. W., Goonhilly, Danbury, Essex. June 28, 1933, No. 18427. [Classes 39 (i) and 40 (v)] Modulation of a magnetron oscillator is effected by simultaneous control of the anode voltage and the magnetization field. As shown in Fig. 2, the split anodes 2, 3 are connected to opposite sides of a tuned circuit which has its mid-point connected through a high-tension source 7, 8 to the cathode 11. The anode circuit also includes the field coil 6a, and a modulating-choke 6b, and the modulating- voltage 10 is applied to the grid of a triode 9 which has its plate connected to a point between the coils 6a, 6b. The coil 6a may be omitted, and the choke 6b utilized as the field coil ; or the choke 6b may be transformer coupled to the field coil. In Fig. 5, series modulation is employed, and, the field coil 6d is in series with the discharge paths both of the magnetron 1 and of modulating triode 9 ; or the field coil may be energized by the secondary of a transformer, the primary of which is in series with the elements 1, 9. In another arrangement, the modulating voltage is applied to a primary coil, and the secondary coil constitutes the field coil of the magnetron. A polarizing field coil 12 separate from the modulating coil is preferably employed. The field magnet may have an open rectangular core 13, Fig. 3, with inwardly-projecting poles 15, 16 between which the magnetron 1 is placed. The polarizing coil 12 and modulating coil 6a surround the respective poles. In the magnetron shown in Fig. 8, the glass envelope 16 is sealed to knife-edge extensions on end-caps 17, 18 of magnetic material preferably nickel-iron between which the filament 19 is supported. The leads to the anodes 20 are taken through the sides of the glass envelope. The end-caps may be recessed as shown to correspond to the shape of the pole-pieces 21, 22 of the magnet. Alternatively, the end-caps and the polepieces may be flat and separated by insulation (Fig. 7 not shown). In another modification, an envelope having the usual re-entrant foot may be used, and two blocks of magnetic material may be supported inside the valve close to the walls with the filament stretched between them. The blocks thus form extensions of the polepieces of the external magnet. Specifications 397,036 and 399,579 are referred to.