Noise in Nonlinear Oscillators

Abstract

A method is presented for estimating the nonlinear noise contribution in an oscillator at low levels of oscillation. This involves obtaining an approximate solution of a nonhomogeneous van der Pol type of nonlinear differential equation driven by noise. The method of solution is based upon the reduction of the equation to a linear form. The nonlinear contribution can then be obtained by computing the power spectrum output of a cube law rectifier. The calculations indicate a variation of nonlinear noise with rf level. Such variation is observed in nuclear and electronic magnetic resonance devices used for the detection of magnetic absorption in paramagnetic materials.