Phase Derivative Approach for Nonlinear Power Amplifier Forward Modeling with 2-D LUTs

In this paper, we propose a new 2-dimensional (2-D) lookup table (LUT)-based scheme with spline interpolation for the modeling of wideband and heavily nonlinear power amplifiers (PAs). The spline-interpolated LUT offers a computationally light yet accurate formulation for the nonlinear characteristics, and, unlike previous such models, we incorporate the phase change information into the modeling, in addition to the traditional signal envelope. RF measurements conducted with contemporary PA systems at 3.5 GHz indicate a clear benefit in including the phase information to the algorithm. Specifically, above 2 dB improved normalized mean squared error (NMSE) and above 3 dB improved adjacent channel error power ratio (ACEPR) are obtained compared to a LUT model without the phase derivative. Moreover, it is shown that the proposed model can outperform the traditional polynomial models with much reduced computational load.