Short and Long-Term Memory Modelling via Generic FIR Filtering

This paper discusses the ability of a generic nonlinear FIR model to represent microwave systems showing simultaneous short- and long-term memory effects (denoted multi-rate systems), such as wireless power amplifiers, PAs. The main problem arising from generic FIR modelling of multi-rate systems is the huge number of parameters that are required to correctly model the system, especially in the nonlinear case. This is a major handicap for both model extraction and for achieving simulation times within reasonable values. This paper demonstrates that for the conditions frequently encountered in practical wireless PAs, the number of model parameters is in fact so huge that makes the generic FIR modelling technique impracticable. Hence, alternative guidelines to avoid this problem are also presented in the paper