ISBN 9783843958141

978-3-8439-5814-1, Reihe Elektrotechnik

Andreas Illmer
Adaptive Linear Drive of GaN-on-Si Doherty Power Amplifiers for 5G Applications

163 Seiten, Dissertation Universität Erlangen-Nürnberg (2026), Softcover, A5

Zusammenfassung / Abstract

This dissertation introduces an adjustable splitter architecture for Doherty power amplifiers in 5G New Radio base transceiver stations. The concept combines drain voltage switching with adaptive control of the drive conditions to enhance efficiency over a wide output power range. Depending on the required output power, the drain voltage is switched between a nominal and a reduced level, improving efficiency at lower output powers. Since this reduction alters the optimal excitation of the Doherty amplifier, conventional fixed analog splitters become suboptimal. The proposed splitter therefore adjusts the relative phase and the power ratio between the Main and Auxiliary paths, adapting the drive conditions to the selected drain voltage. The concept was evaluated in a measurement campaign using a gallium nitride-on-silicon Doherty power amplifier with independently driven inputs to determine the required parameter ranges and resolutions. A dedicated dual-input measurement setup and a novel calibration routine were developed, enabling accurate characterization under modulated excitation while continuously verifying calibration integrity. Reducing the drain voltage from 28 V to 18 V increases the frequency-averaged modulated power added efficiency by 2.5 percentage points for a 20-MHz signal at reduced output power of 4 W instead of the nominal 8 W. Additionally adapting the power ratio and relative phase raises the total improvement to 4.9 percentage points compared to nominal operation, validating the need for adaptive drive control. Only moderate resolution is required, with phase steps of 5.625 degrees and power ratio increments of 0.2 proving sufficient. To the best of the author's knowledge, this work represents the first dual-input measurement study based on gallium nitride-on-silicon technology and the first systematic investigation of linearizability as a function of drive conditions and drain-voltage-dependent splitting parameters of Doherty power amplifiers.