I. Introduction
System-Level behavioral modeling consists of constructing a black-box analytic function that admits alike responses to those obtained at the output of a real device or a subsystem driven by the same input signal. Such models are of great help for designers of communication systems, in particular, transmitters and power amplifiers (PAs) since they provide them with greatly reduced complexity and time-consuming design and optimization procedures. However, these advantages could be achieved providing the capacity of the model to predict the PA output under realistic conditions.