The evolution of cellular wireless communication networks toward distributed MIMO infrastructures requires a rethinking of antenna architectures to adapt them to advanced signal-processing strategies and to ensure optimized, continuous, and robust connectivity. In this context, the use of new frequency bands around 7 GHz opens new opportunities for the development of compact antenna architectures capable of increasing antenna directivity, generating multiple beams, and electronically steering them in different angular directions, both at the user-terminal level and at the radio access points that are expected to become increasingly dense in future networks.

The objective of this PhD thesis is to develop a compact multi-port antenna solution adapted to a hybrid analog-digital beamforming strategy, enabling the transmission of independent data streams while optimizing the spectral and energy efficiency of the communication link. The proposed approach will rely on an original multi-beamforming concept combining superdirectivity with a high-efficiency radiating surface.

The development of such a solution raises several scientific and technological challenges that must be addressed jointly with the development of the required analysis, modelling, and design tools. Particular attention will be devoted to the control of electromagnetic coupling between the different ports of the MIMO antenna, as well as to the energy consumption of the complete electronic system required for multi-beam generation and steering.

The research work will be organized around the following activities:

- State-of-the-art analysis of scientific and technological developments related to distributed MIMO networks, compact antennas, superdirectivity, and hybrid and multi-beamforming techniques.
- Development of numerical tools for antenna analysis, design, and optimization, including approaches based on spherical-wave decomposition and characteristic mode theory.
- Electromagnetic simulation and evaluation of antenna architectures for multi-beam generation and beam steering. This activity will investigate, in particular, holographic-volume architectures based on the concept of superdirectivity, canonical unit cells, and electronic beam-control architectures. Particular attention will be paid to controlling the electromagnetic coupling between the different antenna ports.
- Design of a compact electronically steerable multi-beam antenna system, including the design of the radiating cells, the development of a low-power RF control architecture, the optimization of the control electronics, and prototype fabrication.
Fabrication and experimental characterization of the electronically steerable multi-beam antenna system, including the evaluation of its radiation performance, port-to-port coupling, directivity, angular scanning capability, and power consumption.

The research will be conducted within the framework of the EXCELL-FR3 project, funded by the PEPR Future Networks program under France 2030.