Digital Predistortion for Microwave Transmitters

Abstract

Microwave transmitters comprise the cascade of several subsystems. Among these subsystems, the power amplifier (PA) is identified to be the main source of nonlinearity. Thus, modeling and compensating for the transmitter nonlinearity is often trimmed down to the modeling and compensation of the power amplifier's nonlinearity. Such compensation allows for the use of power‐efficient and nonlinear PA topologies, which results in reducing the energy consumption and cost of wireless transmitters. This article gives an overview of the nonlinear PA behavior and the origins of intermodulation distortions in this subsystem. It defines the most used distortion quantification metrics and the different types of distortions. Power amplifier modeling and digital predistortion principles are explained. The procedure and identification steps of digital predistortion are highlighted, and the different models used in digital predistortion technique are covered. Advanced digital predistortion models for linearizing the impairments in multiple‐input–multiple‐output (MIMO) PAs, dual‐band PAs, and quadrature modulators are also covered.