Advanced design of an extended GaN HEMT Doherty amplifier using uneven saturation power for WiMAX applications

This paper reports the advanced design of an extended GaN HEMT Doherty power amplifier (DPA). For high efficiency over a wide output power range, the DPA is designed using two cells with uneven saturation power (P_sat). A cell with lower P_sat is used as the carrier cell. For experimental validations, the carrier and peaking cells are designed and implemented with 25-W GaN HEMTs at world interpretability for microwave access (WiMAX) band of 2.6 GHz, and then show the P_sat of 40.9 dBm and 43.8 dBm, respectively. For the proposed DPA, the continuous wave results show the power-added efficiency (PAE) of 37.5% at an output power of 36 dBm (10-dB back-off power from P_sat). For a WiMAX signal, the PAE of 36.9% with an relative constellation error (RCE) of -31 dB is obtained at 36 dBm, which is 7.8% improvement compared to the conventional DPA.