Amping Up the PA for 5G: Efficient GaN Power Amplifiers with Dynamic Supplies

Signals designed for high-capacity communications result in high peak-to-average ratio (PAR) waveforms that the transmitter power amplifier (PA) must amplify with low distortion. With emerging fifth-generation (5G) wireless systems, carrier frequencies and signal bandwidths are expected to increase significantly from the current S- and C-band allocations. All these factors are contributing to the increasingly challenging goals of maintaining transmitter PA efficiency for the following reasons: efficiency is not constant over output power; Highly efficient PAs are usually nonlinear; RF load variations can adversely impact efficiency. This article briefly reviews supply modulation to enhance the efficiency of several PA types, followed by a discussion of the main challenges and some predictions about where this technology might be headed in the future.