Continuous Class-J/F<sup>-1</sup> Mode Asymmetrical Doherty Power Amplifier With Extended Bandwidth and Enhanced Efficiency
Jiaxing Sun, Feng Lin, Bo Li, Houjun Sun, Wenhua Chen
Abstract
This article presents a design method of continuous class-J/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> mode asymmetrical Doherty power amplifier (DPA) using the phase tuning technique. By properly adjusting the phase characteristics of the output matching network (OMN) of the carrier amplifier (CA) and the harmonic impedances of the postmatching network (PMN), the load impedance of CA can be effectively tuned to meet the impedance requirements of continuous class-J and continuous class- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> modes at the power back-off point, which thus extends the bandwidth with enhanced power back-off efficiency. In addition, the proposed DPA can theoretically achieve saturation efficiency of more than 58.7% over the working frequency. Based on the proposed method, a broadband continuous class-J/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{F}^{-1}$ </tex-math></inline-formula> mode asymmetrical DPA operating from 1.3 to 2.5 GHz (63%) is designed and measured. Under the continuous wave stimulation, the measured 9-dB back-off, 6-dB back-off, and saturation efficiencies are 55%–62.5%, 52.4%–65.6%, and 62.5%–81%, respectively. The measured 9-dB back-off and saturation gains are 8.8–11.3 and 7–10.6 dB, respectively. When driven by a 20-MHz long-term evolution (LTE) modulated signal with 9.9-dB peak-to-average power ratio (PAPR), the measured average efficiency is 47%–59% and the adjacent channel power ratio is from −23.6 to −31.7 dBc.