An Efficient Load-modulated Outphasing Energy Recovery Amplifier with High Linearity Using a Complex-impedance Rectifier

A high-efficiency outphasing energy recovery amplifier (OPERA) is an attractive system to linearly amplify modulated signals with high peak-to-average power ratios (PAPRs). The deployed rectifier in the OPERA can recover otherwise wasted power from the isolation resistor to boost system efficiencies. However, rectifier performances are limited at high input power over the microwave frequency band. To further improve efficiencies, a load-modulated OPERA using a complex-impedance rectifier is proposed. Theoretical analysis indicates that the output combiner can introduce modulated loads for the OPERA and keep high power combining efficiencies when using the proposed rectifier. For validation, an OPERA system is implemented to deliver peak output power of 39.4-39.8 dBm across 3.35-3.5 GHz, with measured system efficiencies of 65.7%-70.4% at saturation and 40%-42.2% at 6-dB back-off. Excited by a 20-MHz 5G NR signal with 8-dB PAPR, an adjacent channel leakage ratio below -37.2 dBc is realized at 3.5 GHz.