Nonlinear Circuit Analysis

Abstract

The aim of this contribution is to give an introductory approach to the state‐of‐the‐art methods for simulation of nonlinear RF circuits. Time‐domain integration, the shooting methods, harmonic balance, and the envelope transient method are presented, showing their principles and general formulation, together with their advantages and shortcomings, when applied to different kinds of circuits and different regimes. Most aspects of practical simulation are covered, at an introductory level, such as the possible instability and coexistence of solutions, the modeling of distributed elements, or the simulation of circuits containing a large number of devices. One of the objectives is to help the designer interpret the simulation results and choose among the different simulation methods and simulation options, even when using commercial analysis tools. The different simulation methods are presented at two levels. A first level applies to forced circuits, such as amplifiers or mixers. A more advanced level shows how the particular method has to be complemented to be applicable to the autonomous and synchronized regimes, in which practical circuits such as oscillators and analog frequency dividers operate. The different simulation methods are compared by means of their application to a common circuit, exhibiting different operation modes.