Evaluation of Signal-to-Noise and Distortion Ratio Degradation in Nonlinear Systems

Characterization of SNDR degradation in nonlinear wireless transmitters

“…Bussgang's Theorem [2,4] provides the theoretical support for this, since by correlating the output and input signals, we can estimate the effective signal component of the output, and thus by subtraction we can also obtain the uncorrelated part, which is in fact the output nonlinear distortion noise.…”

“…From (5) we can also see that the first term is the linear response, the second and third terms are the correlated part of the output signal (referring the input), 2 and the forth term is the nonlinear distortion correlation, usually called in [3,4] spectral regrowth, which unfortunately also has some correlated components with the linear part of the output. This is in fact one of the major problems of nonlinear systems, that is, how to identify the different signal component at the output.…”

“…Unfortunately in the case of PA having a large impact of memory effects, that is not correct, as the underlying linear system is quite different from a linear well behaved gain [2], and so by applying this feed-forward scheme the output will continue to have a certain amount of correlated distortion that could not be approximated by the delay plus attenuator approach. In memoryless systems, the underlying system gain is normally approached by an attenuator followed by a phase shifter.…”

“…This degradation can be accounted by calculating the Signal to Noise and Distortion Ratio, SNDR [1], defined as [2]:…”

The Dispersion Method for Estimating Non-Linearity of Electro-Acoustic Systems in the Presence of Additive Noise

“…In other words, all the known methods for evaluating nonlinear distortion are very sensitive to the level of additive noise and rather inaccurate. To increase the accuracy in these evaluations, various methods have been proposed, in particular methods of regularization [6], introduction of parametric feedback [7] and others.…”