Relationship between F.M. noise and current noise in a cavity-controlled gunn effect oscillator

A theory is developed to account for the observed ratio of f.m. noise and current noise in a cavity-controlled Gunn effect oscillator. The noise processes are assumed to have their origin in spontaneous fluctuations in the carrier concentration of the GaAs layer which give rise to a modulation of the Gunn diode impedance. The principal parameters of interest in the study are device current and domain capacitance both of which are functions of the carrier concentration n and the internal field F of the GaAs layer. In order to estimate the relative contribution of the two terms in the expression derived for fluctuation in the device an analysis is made of the fluctuation mechanisms in terms of the zero-diffusion model of a propagating domain. It is concluded that the term representing the effect of internal field fluctuations makes only a minor contribution to the f.m. noise and current noise. Experimental evidence is produced in support of the theoretical study and an estimate is made of the carrier concentration fluctuation.