Outphasing Energy Recovery Amplifier With Resistance Compression for Improved Efficiency

We describe a new outphasing energy recovery amplifier (OPERA) which replaces the isolation resistor in the conventional matched combiner with a resistance-compressed rectifier for improved efficiency. The rectifier recovers the power normally wasted in the isolation resistor back to the power supply, while a resistance compression network (RCN) reduces the impedance variation of the rectifier as the output power varies. Because the combiner requires a fixed resistance at the isolation port to ensure matching and isolation between the two outphased power amplifiers (PAs), the RCN serves to maintain high linearity as well as high efficiency in the switching-mode PAs. For demonstration, a prototype OPERA system is designed and implemented with discrete components at an operating frequency of 48 MHz, delivering 20.8 W peak power with 82.9% PAE. The measurement results show an efficiency improvement from 17.9% to 42.0% for a 50-kHz 16-QAM signal with a peak-to-average power ratio of 6.5 dB.