Nonlinear modeling and analysis of a Doherty power amplifier driven by non-constant envelope signals

摘要

A circuit-level CAD method based on circuit envelope (CE) simulation is presented to analyze the nonlinear behavior of Doherty power amplifiers (DPAs) in LDMOS technology, when driven by non-constant envelope signals. In this paper, a general nonlinear model has been extracted for an RF LDMOS power transistor. Then, a complete CE analysis is applied to a designed DPA using the extracted model at 3.5 GHz. To solve the CE equation at specific envelope samples, analytic expressions are developed for the Jacobian matrix and an effective method for quick calculation is suggested. Employing this nonlinear analysis gives insight for optimum design of DPAs and provides an accurate tool to precisely model the nonlinearity of the amplifier in order to predict its distortion effects in modern communication systems.