Development of single-stage and doherty GaN-based hybrid RF power amplifiers for quasi-constant envelope and high peak to average power ratio wireless standards

This article describes the design, realization, and characterization of a set of hybrid medium-power RF power amplifiers, based on a commercial packaged GaN HEMT and developed through a low-cost microstrip process. Two different design solutions suitable for wireless applications are presented: the first, intended for a constant envelope modulation (with reference to the GSM standard) is a Class F amplifier exhibiting at 900 MHz an efficiency of 72% with an output power of 37.5 dBm; the second, optimized for nonconstant envelope signals with high dynamics (with reference to the UMTS WCDMA standard) is a Doherty amplifier showing, at 2.14 GHz, an efficiency higher than 40% at 6 dB of output power back-off with a maximum output power of 40 dB