NARMA-based linearization of RF power amplifiers with non-monotonic response under dynamic hardware reconfiguration

This paper presents a signal processing block intended for a NARMA-based linearization of an RF power amplifier that exhibits a non-monotonic voltage response. This type of response may be obtained when applying a dynamic hardware reconfiguration of the amplifier for power efficiency improvement, through the activation or deactivation of sections in the RF transistor arrays or the electronic tuning of the bias circuits and the impedance matching circuits, as a function of the instantaneous envelope power of the modulated RF signal. A reconfigurable power amplifier design is described as an example of conditions that introduce a non-monotonic voltage response. The need, in that case, to introduce a new function inversion process for NARMA-based predistortion, is highlighted and explained. The proposed inversion process is described mathematically and validated through a power amplifier linearization example.