Frequency modulation system

Abstract

Abstract 571,840. Frequency modulation. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation). Feb. 11, 1944, No. 2543. [Class 40 (v)] An oscillation generator comprising a valve 1, Fig. 2, back-coupled through an artificial line 2 ... 4, 16 ... 18 is frequency-modulated by signal voltages applied to one or more variable impedance valves 12 ... 14 connected in shunt with the shunt resistances of the artificial line. In Fig. 2 the signal voltage is applied to the grids of the triode valves 12 ... 14. In'a modilied arrangement, Fig. 3, the signal voltages are applied through a transformer 25 to the anode circuits of the shunting valves 22 ... 24, the valves being of the pentode type whose anode impedance is proportional to anode voltage. The mean frequency of oscillation is determined by the grid voltage of the valves 22 ... 24, and this is provided by a full-wave rectifier 28, 29 which is fed from the output circuit 26, 27 of the oscillator and has its load resistance 32 connected through a low-pass filter 30, 31 to the valve grids.

Inventors

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