A 4.3-5.6GHz ultra-wideband 10-W GaN Doherty power amplifier with enhanced load modulation bandwidth extension technique

Abstract

In this paper, a design methodology of a novel ultrawideband (UWB) Doherty power amplifier (DPA) monolithic microwave integrated circuit (MMIC) fabricated in a 0.25 µm GaN-HEMT process is presented. To improve the saturated and 6-dB backoff efficiency of the DPA, an ultra-wideband enhanced load modulation technique is presented. A dual-frequency output impedance transformer (OIT) of the peaking amplifier is proposed to extend the enhanced load-modulation bandwidth. For verification, an ultra-wideband high efficiency DPA working over 4.3-5.6 GHz has been designed and fabricated. The measurement results show that the DPA exhibits a small-signal gain of 12.2-14.5 dB, an output power of 39.5-41 dBm, a 6-dB back-off power added efficiency (PAE) of 40.2%-47.4%, and a saturated PAE of 47%-54.6% over the entire band. The proposed DPA demonstrates the highest saturated and 6-dB back-off PAE among published broadband GaN MMIC DPAs operating in similar bandwidth.