The Case for Switched-Mode Transmitter Architectures in Efficient 5G/6G Mobile Networks Based on Power Amplifier Survey

In current mobile networks, the amplification stage is the factor which limits the Radio Access Network (RAN) energy efficiency, with the most impactful blocks being the Power Amplifiers (PAs) and power combiners. This is because available solutions have to accommodate strict linearity requirements, leading to sacrifices in efficiency. A survey was performed for the energy efficiency of common PA solutions, such as standalone, Doherty and outphasing PAs, highlighting how they either fail to offer efficient operation or do so while posing significant trade-offs, which includes addressing the issues with circuit-based power combiners. In alternative, parallel switched-mode PA and over-the-air (OTA) power combination structures are highlighted, which consider the opposite design approach, by maximizing efficiency through simultaneous PA and architecture-level optimizations, then fulfilling linearity requirements through signal processing techniques, meeting the necessary requirements for next-generation mobile networks. Optimizations for further energy-efficiency improvement as well as currently open problems are presented.