A Novel 1.4–4.8GHz Ultra-Wideband, Over 45% High Efficiency Digitally Assisted Frequency-Periodic Load Modulated Amplifier

We report an ultra-wideband and high efficiency sub-6GHz power amplifier, which is based on periodically varied load modulation with frequency. Key novelties are frequency-periodic load modulation over multiple contiguous frequency bands combined with digitally assisted dual-input configuration, which provides optimum signal combination, magnitude and phase of dual-input signals. The amplifier using 0.15-µm GaN HEMT FETs achieved drain efficiency of 45–62% over 1.4–4.8GHz that is 110% fractional bandwidth at 6dB power back-off. This, to the best of the authors’ knowledge, is the widest fractional bandwidth reported so far for a load modulated amplifier at these frequency range. It is a very promising PA technology for 5G base station, enabling reduction of the total cost of ownership (TCO) for operators.