Novel Design Space of Broadband High-Efficiency Parallel-Circuit Class-EF Power Amplifiers

Abstract

This article proposes a broadband high-efficiency parallel-circuit (PC) class-EF power amplifier (PA) along with a quarter-wavelength stub for the first time. By adding a reactive element <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> , the design space is expanded so that the impedance terminations of the fundamental and harmonics are no longer fixed points. Based on the broadband capability of the proposed structure, using a GaN HEMT transistor, a proof-of-concept circuit implemented with the Chebyshev impedance transformation network is designed and fabricated. Experimental results demonstrate a high-efficiency broadband PA operating from 2.6-3.9 GHz, with the average efficiency of 71.5%, the measured output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\textit {out}}$ </tex-math></inline-formula> ) of 38.8-40.9 dBm and the power gain of 8.5-10.6 dB.