A Simple Method of Producing Wide-Band Frequency Modulation

Abstract

THE resistance-capacity tuned oscillator is well known as a very good generator of audio-frequency oscillations. In a recent communication by Rakshit and Bhattacharyya¹ it was pointed out that the conventional circuit of a three-phase system, with components selected for producing audio-frequency oscillations, invariably generates radio-frequencies by virtue of the unavoidable stray and inter-electrode capacities. In fact, with the simple three-phase oscillator it is impossible to generate audio-frequencies unless certain modifications are introduced in the circuit. It was further pointed out that the three-phase radio-frequency oscillator can easily be made to generate frequency-modulated oscillations by varying the tuning resistance of one of the oscillator stages by the modulating voltage.