Dual-Octave-Bandwidth RF-Input Pseudo-Doherty Load Modulated Balanced Amplifier with ≥ 10-dB Power Back-off Range
This paper presents the first-ever dual-octave bandwidth Pseudo-Doherty load-modulated balanced amplifier (PD-LMBA), well-suited for emerging 4G/5G communications and multi-band operations. This design is based on a special bias setting of balanced amplifier (peaking) and control amplifier (carrier), which are combined with proper amplitude and phase controls. The optimal load modulation (LM) of the balanced amplifier can be achieved together with reduced LM factor of the carrier amplifier, leading to maximized overall efficiency throughout extended output power back-off (OBO). With de-coupled cooperation of BA and CA, this architecture fundamentally breaks the bandwidth limitation imposed on load-modulated PAs. To demonstrate the principle, a ultra-wideband RF-input LMBA has been developed using GaN technology from 0.55-2.2 GHz. The experimental results exhibit an efficiency of 49-82% for peak output power and 40-64% for 10-dB OBO, respectively.