Metasurface-based Electronically Steerable Antenna arrays for Next Generation EHF Systems – MESANGES

The use of spectrum in millimeter bands is becoming essential to enable future wireless networks to offer significant capacity gains. However, as propagation losses become significant, antenna and beam formation become key elements in maintaining a reasonable range and limited infrastructure costs. Phased array antenna solutions require a very large number of RF chains and are expensive. The project aims to develop innovative alternative solutions based on reconfigurable metasurfaces. The work will focus on three areas of research: the practical implementation of such antennas in the EHF bands, technical and algorithmic solutions enabling the antennas to address several users simultaneously, and the rapid reconfiguration of the beams adapted to the radio channel.

To reach the aforementioned objectives, the project will first precise scenarios and usages, highlight mmWave radio channel constraints, and provide recommendations on metasurface based antenna design. This will be performed in WP1 during the first 6 months. WP2 addresses the design of electronically steerable antennas based on an array of unit cells having the possibility to reflect/transmit impinging waves from the feeder(s) with a phase shift in a predefined set including zero phase shift. To ensure reconfigurability of these unit cells, a control system will be defined and implemented. Unit cells will be optimized so that their phase shift remains within a given percentage of its nominal values over the bandwidth of interest. Two prototypes will be implemented in WP2: first a full antenna system including an electronically controlled transmitarray, the multi-element focal systems and the digital control will be designed, optimized, fabricated and fully characterized by CEA Leti in the 26-28 GHz band. The antenna system will be able to generate at least four independent beams. The know-how of CEA Leti on transmitarrays is almost unique and has been mostly developed during a long collaboration with the IETR antenna team.

Coding metasurface for cmWave and mmWave are currently developed in DOME group at IEMN. In the framework of a partnership with DGA, the main goal has been to propose artificial structures for Radar Cross Section reduction. In this project, as an alternative to absorbing layers previously studied in the group, the idea is to deviate the incident beam in one or several directions out of the detector spatial range. This approach can also be used to select the beam reflection direction. Regarding the size reduction inherent to frequency increase up to 60 GHz, an external company (INODESIGN) will be in charge of the fabrication. CSAM group of IEMN will bring its expertise in mmWave tune able structures using semi-conductor switching devices. The characterization of the reflectarray will be carried out at the telecom platform of IRCICA institute. To this aim, the 60 GHz anechoic chamber, already available at IRCICA, will be completed with a Newport monitored platform allowing an accurate angular control.

In WP3, BF will be studied for both single and multi-user cases assuming possibly more than one stream per user. The optimization of the grid can be performed off line (using predefined codebooks) or dynamically by applying algorithms such as particle swarm optimization (PSO), genetic algorithm (GA), or deep learning (DL) approaches. The CNAM and Orange will provide their expertise in that domain to design and implement these algorithms.

Performance evaluation of the prototypes and BF algorithms will be performed in a real environment in WP4 with channel sounder, or an SDR approach. This WP will be led by Orange, with contributions of all the partners, to ensure an efficient exploitation of MESANGES results in 5G+ and 6G networks.