Enhanced sensitivity cross-correlation method for voltage noise measurements

Ultralow noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, a new method for the voltage noise measurement is proposed, which allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This is obtained by resorting to the conventional cross-correlation technique for the elimination of the contribution of the equivalent input voltage noise of the amplifiers and by using a new three-step-measurement procedure that exploits different amplifier-configuration measurements in order to subtract the contribution of the equivalent input current noise of the amplifiers.