Correlation technique to reach ultimate resolution in noise measurements

摘要

The Correlation Spectrum Analyzer, thanks to the presence of two independent acquisition channels, has demonstrated to reach very high performance in measuring noise spectra and to be extremely flexible in adapting to different devices under test (DUT) in term of impedance values, of flowing standing current, of DC applied voltage and of the physical quantity to be measured, either current or voltage. In addition, it can selectively extract the noise contribution of a specific current flow in multi-electrodes devices. The paper will briefly highlights these features together with the influence of the DUT characteristics, such as its impedance to ground and the cross-impedance between the two electrodes connected to the instrument input ports, in determining the ultimate limits in the performance of the instrument in terms of its sensitivity, its precision and its spectral extension. A practical realisation for measurements made with an AFM especially modified for correlation investigations is also commented.