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publicly available, any such claims remain unverifiable. The Global Fund and other multi national funding organisations are required to engage in an open and honest dialogue about the impact their investments are making to secure financial commitments by donors into the future. RF received personal fees from the Global Fund for work unrelated to the Results Report 2018. All other authors declare no competing interests.

This paper proposes a modified Doherty power amplifier (DPA) configuration for bandwidth and efficiency operations. To mitigate the efficiency degradation resulting from the incomplete load modulation network (LMN) and the knee voltage effect, the carrier transistor's optimum load impedances based on related constant voltage standing wave ratio (VSWR) circle theory are introduced. Meanwhile, a innovative LMN with broadband matching technologies is adopted, which plays a guiding role on the bandwidth expansion from the theoretical point of view. In order to verify the practical feasibility of the design scheme, two 10 W GaN HEMT transistors are used to design a broadband DPA. The measurement results show that the working bandwidth of the power amplifier is from 1.6 GHz to 2.6 GHz. The saturated output power of the whole frequency band is about 41.7-44 dBm and the drain efficiency (DE) is more than 50.8% at the input power of 33 dBm. In addition, the DE is 41.5-45% at 6-dB back-off power. Measurement results verify that the proposed enhancement techniques of bandwidth and efficiency are effective for DPA.

This paper proposes a broadband Class EF power amplifier based on a low-pass filter matching structure. Based on the theory of Class EF power amplifiers, the optimal fundamental load impedance required is derived. A broadband matching circuit is then designed using a low-pass filter prototype. In the meantime, a compact harmonic control circuit is proposed to meet the harmonic impedance requirements of class EF power amplifiers. In order to validate the effectiveness of the proposed method, a 2.6-3.6 GHz broadband class EF power amplifier is designed and fabricated. Measurement results show that the output power is between 40.68 dBm and 41.6 dBm at 1 dB compression point in 2.6-3.6 GHz. From 62% to 78% drain efficiency is obtained with gain greater than 10 dB.