A SURVEY OF POWER AMPLIFIER SIGNAL LINEARIZATION TECHNIQUES IN COMMUNICATION NETWORKS

Abstract

Radiofrequency power amplifiers are crucial components of communication networks. The inherent nonlinearity of these components causes in-band distortion, which worsens bit-error-rate performance, and spectrum regrowth, which causes interference in adjacent channels. Out-of-band emission requirements set by regulatory bodies are essentially violated by these distortions. At the output of the power amplifier (PA), crosstalk exists between the antenna branches due to mutual coupling and nonlinear distortion within the transmitted signal. Harmonic distortion is a result of the complexity of modern signal processing techniques and the nonlinear nature of PAs. For high spectral and power efficiency, PAs must operate linearly. Electronic isolators between PAs and antennas can prevent this crosstalk. However, they do not meet the design requirements of modern composite systems. They are rather avoided to achieve a suitable form factor. Very useful linearization strategies are therefore presented and discussed in this survey. The effectiveness of PAs, as well as the complexity and constraints of the system, are always taken into account while choosing the linearization approach. These are effective ways to linearize transmit signals from PA output. The techniques are found effectively suitable in all domains while maintaining the acceptable adjacent channel leakage ratio level.