Highly efficient GaN Doherty power amplifier with 100 MHz signal bandwidth for 3.5 GHz LTE-Advanced application

This paper presents a highly efficient GaN Doherty power amplifier (DPA) with 100 MHz signal bandwidth and 40 dBm average output power for 3.5 GHz LTE-Advanced application. The carrier and peaking amplifiers are fabricated using 60-W GaN HEMT and implemented with unequal saturation power (Psat) in order to maintain high efficiency at large backed-off power (BOP). The highest drain efficiency (DE) at 6-dB BOP for continuous wave (CW) signal reaches 52.6%. Meanwhile, the DE achieves 40.2% for 100 MHz LTE-Advanced signal with adjacent channel leakage ratio (ACLR) less than −32 dBc at output power of 40 dBm. Furthermore, the linearization of the DPA is realized by using digital pre-distortion (DPD) technique. The ACLRs are improved to −51.5 and −50 dBc for 40 and 50 MHz LTE-Advanced signal respectively at 40 dBm with DE of 40.5%.