Outphasing Energy Recovery Amplifier With Resistance Compression for Improved Efficiency

Abstract

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.

High efficiency resonant dc/dc converter utilizing a resistance compression network

“…Using fundamental frequency analysis, at the switching frequency the half-bridge rectifiers can be modeled as resistors [8], [16], as illustrated in Fig. 3.…”

“…The use of the resistance compression network reduces the change in impedance seen by the inverter as the effective rectifier resistance (R L ) changes due to variations in output voltage and output power [15], [16]. This compression effect can be seen in Fig.…”

“…The resistance compression network (composed of L s and C s ) is a special single input, multi-output matching network that provides desirable impedance control characteristics [15], [16], [23]. The RCN technique was originally proposed and applied for radio-frequency (RF) applications, such as very-high-frequency dc/dc converter systems [15] and RF power amplifiers [16]; here we exploit if for high efficiency power conversion. The function of the RCN is to automatically regulate the converter operating power and waveforms in a desirable manner as the input and output voltages vary.…”

High Efficiency Power Amplifiers for Modern Mobile Communications: The Load-Modulation Approach

“…In power back-off conditions, all the unnecessary output power from the branch PAs is wasted at the isolating port of the output combiner [100,101]. A possible way to improve efficiency is therefore to rectify the non-used power at the isolated port and reuse it for device bias [102]. However, with this approach, the impedance variation at the isolated port produces an undesired load modulation effect on the two PAs, with negative impact on their efficiency.…”

A New Power Combining and Outphasing Modulation System for High-Efficiency Power Amplification

“…This leads to a rapid degradation of efficiency as output power is decreased, diminishing the attractiveness of this approach [19]. This problem can be partially offset by recovering power not delivered to the output through a rectifier [20][21][22].…”