MMIC Doherty power amplifier for a 5W pico-cell base station in GaN HFET technology

4G standards such as Long Term Evolution (LTE) use non-constant envelope modulation techniques with high peak-to-average ratios. Power amplifiers (PA) implemented in such applications are forced to operate at a backed-off region from saturation. Thus, to reduce power consumption, a design of a high efficiency PA that can maintain the efficiency for a wider range of RF signals is required. In this paper, a two-way 10W Doherty amplifier designed in a compact 10×11.5mm² monolithic microwave integrated circuit using GaN technology is presented. Suitable for a 4G LTE 5W pico-cell base station, which entails the frequencies from 2.62–2.69GHz, the design achieves high efficiencies of over 50% at both back-off and peak power regions without compromising on the stringent linearity requirements of 4G LTE standards. This demonstrates a 17% increase in power added efficiency at 6 dB back-off from peak power compared to conventional Class AB amplifier performance.