Linearization of EER RF power amplifiers using an adaptive subband predistorter

Power amplifiers are a fundamental component for nearly all communications systems. Long-range wireless communications require high-power radio frequency (RF) amplifiers that are by far the most power consuming devices in the entire system. It is well known that efficient power amplifiers are highly nonlinear. However, highly efficient amplifiers such as the envelope elimination and restoration (EER) amplifiers as described herein are critical to mobile communications systems that require low power consumption for increased battery life and reduced size, weight, and power (SWAP), such as cell phones and military radios. The non-linearity of amplifiers generates both in-band noise (IBN) and out-of-band noise (OBN) which causes an increased bit error rate (BER) and adjacent channel interference (ACI), respectively. This degradation in performance has become a critical issue in recent years as newly emerging spectrally-efficient digital waveforms are being used for high-data rate communications. Linearization is necessary to comply with adjacent channel spectral mask requirements, to reduce BER, and to achieve acceptable amplifier efficiency. Predistortion can be used to convert a nonlinear amplifier into a linear amplifier. This paper describes a novel method for linearizing EER RF power amplifiers using adaptive subband predistortion.