Two-Dimensional Fractional Polar Volterra Series for Baseband Power Amplifier Behavioral Modeling

This paper proposes a new behavioral model for radio-frequency power amplifiers (RF PAs) by extending the two-dimensional Polar Volterra series to fractional derivative order, using a numerical Mittag–Leffler-based formulation of fractional orthonormal generating functions. The motivation stems from the increasing need for accurate and computationally efficient models to represent nonlinearities and memory effects in wideband RF PAs, especially in energy-efficient 5G systems. The proposed method significantly reduces model complexity by lowering the number of estimated parameters while maintaining or improving modeling fidelity. To evaluate its performance, three different RF PA devices were used as test cases. The results demonstrated that the proposed approach achieved an over 81.5% reduction in the number of model parameters and improved modeling accuracy. Besides that, in a scenario with the same number of parameters, normalized mean square error (NMSE) gains of up to 8.72 dB were obtained. These findings support the method’s potential for practical use in RF PA behavioral modeling and digital predistortion applications.