TABLE OF CONTENTS In nonlinear circuits, we have two fundamental concerns. The first is to determine the effect of noise in nonautonomous circuits, circuits such as mixers and frequency multipliers, which have external RF excitations. Examples are the noise figure of a mixer or phase noise in a frequency multiplier. The second concern is noise in oscillatory circuits having no external excitation, other than dc bias. Such circuits are called autonomous.
Solid-state devices may have static noise sources, such as thermal noise from parasitic resistances. Other noise sources, however, are functions of the large-signal currents or voltages in the device, and thus are modulated by large-signal voltage or current waveforms. The modulation process, as one might expect, creates noise sidebands around each large-signal harmonic. Less intuitive is the fact that it introduces correlations between those sideband components. Accounting for those correlations is critical to accurate noise analysis of large-signal circuits.
In the linear noise analysis of Chapter 5, we considered only the response of a linear circuit to one or more noise sources. Because the circuit was linear, we were able to ignore sinusoidal or other deterministic excitations. If we were interested in them, we needed only to find the circuit response to those excitations and add them to the noise.
In a nonlinear circuit, the situation is not so simple. We are faced with a circuit that is driven by one or more large signals, and small-signal noise is present...
