Satellites in low Earth orbit will soon need to handle thousands of simultaneous mobile phone calls and video streams, but the power amplifiers that drive their antennas currently waste too much energy to make this work. The problem is a fundamental mismatch in how antennas and amplifiers interact. Today’s satellite engineers place bulky isolators between each antenna element and its power amplifier to prevent interference, but these components block the dense integration needed for direct-to-cell services. When amplifiers face a shifting, non-standard electrical load—as happens during multibeam scanning—their efficiency plummets. This project replaces the traditional fixed 50-Ohm matching approach with a holistic design that accounts for the dynamic “load-pull” interactions between antenna arrays and amplifiers. If successful, the research could cut the energy consumption of low Earth orbit satellites enough to allow deployment of thousands of integrated transceivers per satellite. That would make high-capacity direct-to-cell connectivity feasible for rural areas, flights, and ships at sea—without requiring ground infrastructure. The work is applied engineering, not fundamental science, but it tackles a specific bottleneck that currently blocks a major step in satellite communications.
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Direct-to-cell connectivity is the next milestone for New Space, paving the way toward 6G through low Earth orbit (LEO) satellites to deliver seamless global mobile coverage, including in rural and remote areas, as well as in-flight and maritime communications. To manage the massive data traffic in direct-to-cell services, such as video streaming and internet browsing for numerous mobile users, LEO satellites are expected to highly integrate thousands of transceivers and antenna elements, known as integrated active antenna arrays. This level of integration differs from current practices, where components like ferromagnetic isolators, which are incompatible with high integration, are typically placed between each antenna element and its corresponding power amplifier (PA) to minimise impedance mismatch issues. In the context of antenna mutual coupling, a significant challenge for the integrated active antenna array is the dynamic and nonlinear "load-pull" interactions between the antenna arrays and PAs. The PA loads will shift to other loads and become dynamic instead of remaining at the standard 50 Ohms during multibeam scanning implementation. Since PA performance (i.e., efficiency and output power) relies heavily on the PA load, traditional PA design approaches, which generally focus on fixed 50-Ohm matching, become impractical. In this project, by leveraging knowledge of multibeam antenna arrays and waveform characteristics, a holistic PA design approach for integrated direct-to-cell active antenna arrays will be developed. This innovation will significantly enhance the energy efficiency of integrated active antennas, meeting the strict energy consumption requirements of LEO satellites. As a result, this project will facilitate the deployment of LEO satellites with thousands of integrated active antenna arrays, enabling high-capacity direct-to-cell connections.
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