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Oscillations in Systems with Non-linear Reactance

01 July 1936

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A T Y P E of free oscillation has been found to occur in non-linear coupled systems, which differs from the ordinary type in that the supporting energy is drawn from an alternating sustained source, rather than from a constant source, as in the ordinary vacuum tube oscillator. The particular example of such oscillations to be described here occurs in an electric circuit containing a condenser, one plate of which is elastically supported so as to constitute a mechanically resonant system. The possibility of such oscillations in a circuit of this kind was discovered 1 in the course of a theoretical study of the possible use of a moving plate condenser as a modulator in a carrier system. Such use was suggested by the fact that, in a condenser, the mechanical force on the plate is proportional to the square of the charge. In this study, it was assumed that a generator of alternating electromotive force of a relatively high carrier frequency was connected with the condenser terminals, and an alternating mechanical force of a relatively low frequency (corresponding to a Fourier component of a speech wave) was applied to the movable plate of the condenser. The plate was not assumed to be resonant. The non-linear relations between 1