A 2.14-GHz GaN MMIC Doherty Power Amplifier for Small-Cell Base Stations

A novel 2.14-GHz Doherty power amplifier (PA) was designed and fabricated using a 0.25-mu m GaN on SiC monolithic microwave integrated circuit (MMIC), to build small-cell base stations. To reduce the size and loss, lumped passive elements were employed in a manner of minimizing the device count. The core components of the PA were integrated on the MMIC die to reduce the area, and low-loss chip inductors were mounted around the die to enhance the efficiency. An unconventional uneven power splitting was also used to enhance the performance. For a continuous wave, a 2-dB-gain-compression power of 40.5 dBm was obtained with a drain efficiency (DE) of 60.4%. At 7.3-dB backed-off power, a DE of 52.2% was obtained with a power gain of 15.7 dB. When a 10-MHz-bandwidth long-term evolution signal with 7.1-dB peak-to-average power ratio was applied, an adjacent channel leakage ratio (ACLR) of -34.7 dBc with a DE of 51.8% was achieved at an average power of 33.2 dBm. After a digital pre-distortion process, the ACLR and DE were improved to -49.6 dBc and 52.7%, respectively.