GB540828A - Improvements in impulse modulation of high frequency oscillators - Google Patents

Abstract

540,828. Valve modulating circuits MARCONI'S WIRELESS TELEGRAPH CO., Ltd. April 29, 1940, No. 7659. Convention date, April 29, 1939. [Class 40 (v)] For economizing power in an impulsemodulated magnetron oscillator, the magnetron anodes are directly supplied from a D.C. source during the impulses, whilst the electro-magnet is supplied with current from a condenser which is charged from the D.C. source during intervals between pulses. The modulating source 39 supplies sinusoidal voltages to the grid of a waveshaping valve circuit 47 which during each positive half-cycle supplies a flat-topped positive pulse to the grid of a valve 45. Current then passes from the source 35 through the valve 45 into the condenser 43. During the opposite half cycle the condenser 43 discharges through the magnetizing winding 31 of the magnetron oscillator 7, and through a pentode valve 49 the grid of which has been rendered positive by a shaping circuit 51 supplied from the modulating source 39. Impulses are also applied through a delay network 41 and a shaping circuit 37 to a modulating valve 33 which causes D.C. voltage to be applied to the end-plates 9, 11 of the magnetron slightly later than the electromagnet winding 31 is energized, thereby causing the emission of a pulse of carrier wave from the aerial 19.