Bandwidth Extension of Three-Way Doherty Power Amplifier With Reactance Compensation Using Parallel Peaking Amplifiers
Wa Kong, Jing Xia, Xin Yu Zhou, Tianqi Zhang, Wence Zhang, Xu Bao
Abstract
This paper presents a new methodology for designing a broadband three-way Doherty power amplifier (DPA), which utilizes a reactance compensation generated by parallel peaking amplifiers to extend the bandwidth and improve the back-off efficiency. By analyzing the load impedance and efficiency of the reactance-compensated DPA, the optimal reactance at the output of the peaking amplifier required for bandwidth extension can be obtained. Then, a structure using two parallel peaking amplifiers is proposed to reduce the output reactance for the desired distribution. Using a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> /4 transmission line, a sufficiently large output reactance of the peaking branch can be realized at the combining point over a wider frequency band, which can compensate the effective load impedance of the carrier amplifier and improve its efficiency and bandwidth. A wideband three-way DPA is designed and fabricated to verify the proposed method. Measurement results indicate that an efficiency of 50–53% at 10 dB output power back-off and a saturated efficiency of 54–68% can be achieved over the frequency range from 1.6 to 2.7 GHz.