The Evolution of PA Linearization: From Classic Feedforward and Feedback Through Analog and Digital Predistortion

This article reviews the history and concepts behind the linearizers in use today. Predistortion linearization is by far the most widely used form of linearization and is most commonly generated digitally (DPD) for use in telecommunications and relatively limited bandwidth applications. The future for DPD looks bright, with new developments in software and hardware and exciting opportunities for disruptive approaches to be successful. For wider bandwidths, analog predistortion is often used. Rapid progress is being made to produce linearizers of very wide bandwidth and to extend their capabilities to the upper millimeter-wave bands. Multi-octave analog predistorters with greater than 10 GHz of bandwidth and that operate to 100 GHz have been produced.