Small-signal and large-signal noise analyses of nonlinear circuits in frequency domain

The problems of a noise analysis of nonlinear circuits for small and large signal levels are surveyed. It is shown, that the known method of correlation analysis of linear circuits requiring knowledge of the correlation matrices of all elements of the circuit can be implemented at a level of primary sources of noises of each circuit element. Such an approach essentially simplifies a mathematical and algorithmic realization of the analysis, dilating its possibilities on all devices, for which the equivalent noise circuits are known but the correlation noise matrix is not obtained. The nonlinear analysis of nonlinear circuit noise is discussed. The method of nonlinear noise analysis based on canonical decomposition of spectral densities of the circuit's noise sources is presented. The method, contrary to the LSSS method, widely used in the programs for the nonlinear analysis of microwave and RF circuits, allows effectively to parse both poorly "rustling" circuits, and circuit with a very high noise level, when the nonlinearity of the circuit in relation to noise cannot be neglected.