Broadband GaN Class-E Power Amplifier for Load Modulated Delta Sigma and 5G Transmitter Applications

Abstract

The paper presents a design of a broadband high-efficiency class-E power amplifier (PA) for the advanced efficiency enhancement architectures applications. A sequential load pull methodology to design broadband class-E power amplifiers using a packaged gallium nitride power transistor is presented. Two different broadband matching synthesis techniques have been proposed using lumped elements have been presented and implemented in the manuscript. A fourth-order low-pass impedance transformation topology is designed as the output matching network to provide the optimum load reflection coefficients in the targeted bandwidth (1.8-2.7 GHz). A combination of input and output matching network has been proposed in the manuscript to satisfy the given fractional bandwidth requirements. For practical validation, a Wolfspeed (Cree) CGH40025 package transistor has been used. Under continuous wave test condition the fabricated PA showed more than 50% power added efficiency (PAE) with up to 29 W output power for 40% fractional bandwidth from 1.8-2.7 GHz. Furthermore, the proposed broadband Class E PA is deployed in efficiency enhancement architecture like delta-sigma modulation based transmitters. The PA shows more than 48% PAE all over the frequency band when driven with a delta-sigma modulated LTE downlink signal while maintaining high signal quality and PA reliability.

Keywords

• broadband
• class-E
• delta-sigma
• gallium nitride (GaN)
• lumped element
• microstrip