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Patent

FM Modulator using variable transistor capacitance

TLDR
In this article, a variable capacitance transistor is used to vary the oscillation frequency of an oscillating transistor in an FM modulation circuit. But the transistor has resistors connected between the emitter and base and between the collector and base, respectively.
Abstract
In an FM modulation circuit, a variable capacitance circuit employs a transistor as a variable capacitance element. The transistor has resistors connected between the emitter and base thereof and between the collector and base thereof, respectively, and is connected under the unbiased state to an oscillating transistor of an oscillation circuit constituting the FM modulation circuit. In correspondence with an input signal applied across the emitter and collector of the variable capacitance transistor, the emitter--collector capacitance of this transistor is varied to vary the oscillation frequency of the oscillation circuit.

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Voltage controlled oscillating circuit

TL;DR: In this paper, a variable capacitance element is provided by a bipolar transistor and the capacitance of the element is achieved by combining capacitance by the PN junction between the emitter layer and the base layer and capacitance formed by the pN junction in the bipolar transistor.
References
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Patent

System for processing and transmitting audio signals received from a television set for reproduction by a high fidelity FM receiver

TL;DR: In this article, an audio signal coupling and processing system for reproduction of TV audio without direct connection between the television set and the high fidelity system is presented, which includes a first antenna tuned to receive the radiated FM audio signals from the television receiver, circuitry for demodulating, de-emphasizing, and then prephasizing the sensed FM signals, an FM modulator for frequency modulating about a carrier frequency at a selected point within the 88-108 megahertz band.
Patent

High modulation index oscillator-modulator circuit

C Rosen, +1 more
TL;DR: In this article, an oscillator-modulator circuit is described where a high modulation index is obtained by shunting across the crystal of the oscillator a first capacitance derived across the output terminals of a modulation amplifier transistor and a second capacitance generated by the input terminals of oscillator transistor, such first and second capacitances being time varied by the modulation signal.