Aligned Current Response in Peaking Way of Doherty Amplifier to Improve the Efficiency Consistency for LTE Advanced Application

This paper proposed a design method to improve the load modulation mechanism and efficiency of Doherty by adopting the broadband input matching circuit to align the output current of peaking power amplifier (PA). From analytical investigation, the current response of the peaking PA in Doherty gives an inconsistent turn on behavior due to the deep class C bias condition. To remove this inconsistent turn on behavior, simplified real frequency technique (SRFT) is proposed. To verify this proposed method, two Doherty PAs with different input match are designed to work at 2. 15GHz for comparison. These simulated and measured results show that the output of PAs is higher than 49dBm. At 7dB backoff power region, PA with broadband input matching gives a lowest efficiency of 42% and an improved efficiency deviation from 10% to 2% in working band. Excited by 100MHz LTE A signals, with digital predistortion (DPD) PA presents an higher and lower band ACLR of -45. 1/ -44.9dBc around output power of 40dBm and efficiency of 40.5%, which is both better than narrow band design.