Novel digital microwave PA with more than 40% PAE over 10 Db power back-off range

This paper presents a novel GaN-based digital power amplifier (PA) circuit with a high overall power-added efficiency (PAE) over a 10 dB power back-off range for the 800 MHz LTE-band. It includes an optimized 2%-stage driver circuit for a push-pull final-stage with minimized losses proposed for the first time. High PAE is reached by resonant commutation of the final-stage and a novel driver circuit for the upper finalstage transistor. Applying a PWM input signal the digital PA achieves an overall PAE of 48% and 40% at 6 dB and 10 dB power back-off, respectively. PAE peaks at 62% while maximum output power is 4.7 W. This is the first digital PA exhibiting a very low PAE-drop of only 19%-points over a 10.5 dB power back-off range. These results are competitive to the common analog PA concepts while maintaining higher flexibility and compactness.