Broadband continuous Class-J GaN Doherty power amplifier using phase-controlled impedance synthesis methodology

Abstract

This letter presents a broadband GaN Doherty power amplifier (DPA) operating in continuous Class-J mode using a phase-controlled impedance synthesis methodology. The proposed method simultaneously constrains both fundamental and second harmonic impedances, explicitly incorporates the carrier amplifier’s intrinsic parasitic impedance, and performs a global co-design of the phase compensation line, output matching network, and post-matching network. The DPA achieves 60–80% drain efficiency at saturation and 45–58% at 6 dB back-off across 1.6–2.9 GHz (58% fractional bandwidth), with 12–13 dB gain and 43–44.5 dBm saturated output power. The moderate back-off efficiency variation reflects the inherent wideband design trade-off. Under a stringent 100-MHz 5G NR signal without digital predistortion, the ACPR ranges from −37.5 to −22.5 dBc at 36 dBm average power.