Symmetrical Doherty Amplifier with High Efficiency over Large Output Power Dynamic Range

For the conventional Doherty power amplifiers, asymmetrical cells are used to achieve high efficiency over large (> 6 dB) output power dynamic ranges, i.e. larger class-C cell. In this paper, it will be theoretically proven that high efficiency over large dynamic ranges also can be achieved using symmetrical devices, while still maintaining full voltage and current swing of both transistor cells. Using a smaller class-C cell compared to the asymmetrical Doherty has the advantages of higher gain and power added efficiency (PAE). The proposed symmetrical Doherty concept is experimentally verified by a 3.5 GHz 28 Watt circuit demonstrator fabricated using identical GaN HEMT devices. An average power added efficiency of 52 % and adjacent power leakage ratio of -52 dB is obtained with 9 dB peak-to-average power-ratio 20 MHz LTE test signals.