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Enhancement of the broadband efficiency of a class-j power amplifier with varactor-based dynamic load modulation

: Amirpour, Raul; Darraji, Ramzi; Ghannouchi, Fadhel; Quay, Rüdiger


IEEE microwave and wireless components letters 27 (2017), No.2, pp.180-182
ISSN: 1051-8207
ISSN: 1531-1309
Journal Article
Fraunhofer IAF ()
class-J; DLM; GaN; power amplifier (PA); varactor; wideband

A broadband Class-J power amplifier (PA) with dynamic load modulation (DLM) is presented. It is theoretically shown that a PA with judicious variation of the load resistance and a purely reactive load modulation can maintain 70% drain efficiency over 73% fractional bandwidth and 8.5 dB dynamic range. The theory is verified by a demonstrator PA based on a gallium nitride (GaN) device and a varactor as the tuneable element. The load modulation shows good results from 1.7 GHz to 2.3 GHz and up to 50% of power added efficiency (PAE) is obtained. It is shown that the average PAE for a modulated signal with 7 dB peak-to-average ratio is improved by 15%.