Efficiency vs. linearity trade-offs in outphasing power amplifiers

This paper presents an investigation of the trade-offs between efficiency improvement and linearity of the outphasing power amplifier. Simulations and experimental measurements are carried out to validate the theoretical analysis. Two types of digital modulation signals are used, namely 16-QAM and 64-QAM. The impact of the stub length on the efficiency and linearity is studied for both signals. Different Chireix combiners having stubs of varying electrical lengths combiners are fabricated for experimental validation of the theoretical results. The work shows that a trade-off can be made between efficiency and linearity, as measured by the error vector magnitude (EVM), for a given signal by proper choice of the outphasing combinerpsilas reactances. The resulting combiner ensures signal transmission with the maximum efficiency that meets the established linearity requirement.