Non-linear models for High Power Amplifiers

In this chapter we start by developing the analytical formulation of a general structure for the nonlinear distortion. This formulation, based on the Volterra series expansion, is provided in order to demonstrate the validity of some classical approximations concerning the use of higher order nonlinear models for HPA characterization. Then, one of the most validated HPA models is described in some detail for its later use in our simulations. The theoretical relations between its direct and inverse characteristics are included since they constitute an important qualitative reference for the pre-distortion algorithms. Finally, some foresight about certain limiting aspects on the invertibility of complex nonlinearities is given and some graphical examples are briefly discussed.