Millimeter-Wave High-Efficiency Doherty Power Amplifiers in Gallium Nitride High-Electron-Mobility Transistor Technology

The global demand for high data rates is pushing wireless systems into the millimeter-wave (mm-wave) band, where broader spectrum bandwidths can unlock the potential of 5G and future 6G. However, this shift creates a critical efficiency challenge for the power amplifiers that form the heart of base stations. This work addresses the urgent need for energy-efficient amplification to ensure sustainable, high-performance next-generation networks. This dissertation presents a comprehensive advancement in the design of high-efficiency Doherty Power Amplifiers (DPAs) using Gallium Nitride (GaN) technology for mm-wave applications. It introduces innovative solutions to the key limitations of efficiency, bandwidth, and gain. Through novel harmonic-tuning networks and second-harmonic injection techniques, the research delivers state-of-the-art prototypes. Demonstrators like the SAFI DPA achieve record-breaking performance, covering crucial 5G bands with exceptional power-added efficiency and circuit bandwidth. The work establishes a foundational design framework, paving the way for energy-efficient mm-wave transmitters that reduce operational costs and environmental impact.