Improvement of the accuracy of noise measurements by the two-amplifier correlation method

Abstract

We present a novel method for device noise measurement, based on a two-channel cross-correlation technique and a direct "in situ" measurement of the transimpedance of the device under test (DUT), which allows improved accuracy with respect to what is available in the literature, in particular when the DUT is a nonlinear device. Detailed analytical expressions for the total residual noise are derived, and an experimental investigation of the increased accuracy provided by the method is performed.

Performance analysis of correlation techniques for noise measurements

“…In most digital signal analyzers, an internal programmable signal source (V s ) with a white spectrum is available, which allows the direct measurement of H 1 and H 2 . As can be seen from the expressions for the K Ii and K V i coefficients determined in [3], the K Ii terms are much smaller than unity, while the K V i are of the order of 1/R 2 d . Thus the contributions from the current noise sources are strongly suppressed, while those from the voltage noise sources are substantially the same as without cross-correlation.…”

“…In a recent paper [3] we have shown that the equivalent cross-spectrum S I12 at the DUT can be expressed as…”

“…In [3] it was also shown that, in the case of the parallel configuration, the total cross-spectrum can be expressed as…”

“…(as shown in [3]), thus the cross spectrum resulting from the DUT source and from the residual correlated noise components (S res ) would be real, because the imaginary part would vanish. In this (ideal) case we would obtain…”

“…For the series configuration, for example, an estimate S single of the cross spectrum obtained from a single time series reads [3]:…”