A 3-bit, 2-watt, digital-analog gallium nitride power amplifier for 64-QAM bandwidth efficient modulation with 25% power savings

A 3-bit digital-analog power amplifier using 28-V 0.2-μm AlGaN/GaN HEMT, for high-power, high-rate, linearized transmitters, is presented. Efficient amplification of complex digitally-modulated RF signals is achieved using a constantly active main transistor cell and 3-bit unary-weighted, digitally-controlled auxiliary cells that are enabled/disabled based on signal envelope power. The auxiliary cells efficiently linearize the AM-AM response, compensating for gain compression and extending P1dB by 2.5dB. Dynamic simulations with a 50MHz, 64-QAM signal predict 50% EVM
_RMS
improvement and 25% power savings compared to a Class-A amplifier. Static measurements of the digital-analog power amplifier demonstrate 9.6dB linear gain, 2.2W P
_1dB
, and 39.3% PAE
_P1dB
at 7GHz.