Behavioral Modeling and Predistortion of Wideband Wireless Transmitters

Chapter 2Dynamic Nonlinear Systems

In Chapter 1 a description of a nonlinear system, the power amplifier, along with the effects that it introduces to the communication signal, is presented. Characteristics of this nonlinear system were also presented in detail along with the metrics to quantify the amount of nonlinear distortion. In this chapter, dynamic nonlinear power amplifiers will be introduced. First, the notion of memory in systems will be defined. Then a classification of nonlinear power amplifier systems based on their amount of memory will be provided. The origins of the linear and nonlinear memory effects and their characteristics will be addressed. A general model based on the Volterra series to model power amplifiers with memory effects will be introduced. Its pass-band time domain representation and its baseband equivalent model will be also provided.

2.1 Classification of Nonlinear Systems

Memory in systems can be defined as the ability of a system to behave as a function of values of the input signal that are different than the present value of the input signal. Therefore, systems can be classified in two groups: memoryless systems and systems with memory [1–4].

2.1.1 Memoryless Systems

In general, a system is said to be memoryless if its output at a given time , , is a function of only the input value at , .

For practical considerations, every physical system ...