Analysis and Development of a Two RF Input Load Modulated Envelope Tracking PA

This work introduces the load-modulation technique to improve the power handling capabilities of envelope tracking (ET) power amplifiers. It is based on an auxiliary amplifier capable to inject at the main amplifier output terminal a copy of its input signal, properly phased and scaled in magnitude. By this approach, the ET output termination can track the bias supply thus maintaining the maximum dynamics of both current and voltage at the device output terminal. The proposed load-modulated envelope tracking (LM-ET) is demonstrated through the design analysis, and the development of a prototype characterized in the 3600 – 3800 MHz frequency bandwidth. Experimental results demonstrate an improvement of 3 dB at 5 dB power back-off maintaining the overall efficiency degradation of maximum 9%.