Design and Implementation of a High-Power and High-Efficiency RF Class-E Parallel Amplifier with Hybrid Coupler Using GaN HEMT Transistors for Wireless Power Transfer

Abstract

Rapid advances in wireless energy technology have increased the demand for highly efficient RF power amplifiers capable of handling high power for Wireless Power Transfer (WPT) systems. This study presents the design and implementation of a high-power RF amplifier based on a parallel Class-E topology that integrates a hybrid power combiner, using GaN HEMT transistors. The proposed architecture aims to overcome the power capacity limitations of a single Class-E amplifier by connecting multiple transistors in parallel and combining their outputs through a low-loss -3 dB hybrid combiner, allowing for a higher total output power while maintaining excellent operational efficiency and stability. GaN HEMT transistor technology is applied due to its superior electrical and thermal properties, such as high breakdown voltage, high current density, fast switching operation, and better thermal resistance. These characteristics make GaN devices suitable for Class-E operation at high voltages (28 V) with output power above 10 W and power added efficiency (PAE) exceeding 80%. The comprehensive design process includes non-linear device modeling, Class-E load network synthesis, hybrid coupler optimization, impedance matching, and electromagnetic co-simulation using Advanced Design System (ADS). This power amplifier is implemented on a Rogers RO4350 20 mils substrate with a PCB layout optimized for current distribution, minimal input loss, phase symmetry, and thermal management. Practical measurements confirm efficient power combining, stable amplifier operation under load variations, and reliable thermal performance under continuous high-power conditions. The developed amplifier offers a practical and scalable solution for high-power WPT transmitters that can be used in wireless electric vehicle charging, UAV power transmission platforms, and renewable energy distribution systems in remote areas, setting a new standard in RF efficiency, power density, and operational reliability.