A High Efficiency 3.6-4.0 GHz Envelope-Tracking Power Amplifier Using GaN Soft-Switching Buck-Converter

We report a high efficiency sub-6GHz wideband Envelope-Tracking Power Amplifier (ET-PA) including a soft-switching buck-converter and a wideband RF-PA, used in conjunction with a digital front end (DFE) environment for signal generation and predistortion. Both buck-converter and RF-P A were fabricated using an 0.15um GaN HEMT process. The DFE can generate the input signals for both buck-converter and RF-P A, capture the output signal for feed-back and perform digital predistortion (DPD). The overall ET-P A achieves total efficiency of 39.5-46.7% and output power of 31.2-31.5dBm over 3.6-4.0GHz with 20MHz L TE signals. With DPD, ACLR was below -45dBc with total efficiency reaching 47% at 3.6GHz. This, to the best of the authors' knowledge, is the highest efficiency yet reported for an ET-PA at this carrier frequency.