Analog & Digital Envelope Tracking Power Amplifier Reduced Bandwidth Techniques for 5G NR

Envelope tracking power amplifiers (ETPAs) with either analog or digital modulators are described and compared, with emphasis on 5G NR applications. The analog modulator reproduces the envelope amplitude signal with a goal of higher fidelity, while digital envelope modulators produce a discrete stepwise approximation of the envelope signal with a goal of higher efficiency. Analog series-parallel hybrids vs digital power-DACs, tap-changers, and multi-switchers, paired with RF power amplifier such as Class J, E, or F will be reviewed. Linearization schemes for the analog and digital techniques will be shown, with memory effect mitigation and adaptive digital predistortion, including multidimensional linearization for reduced bandwidth envelope tracking.