Building a Smart EM Environment - AI-Enhanced Aperiodic Micro-Scale Design of Passive EM Skins

Multi-Scale Single-Bit RP-EMS Synthesis for Advanced Propagation Manipulation through System-by-Design

“…Several research studies on the foundation, the modeling, the simulation, the design, and the test of EMSs are currently under development with a strong interdisciplinary effort combining chemistry, physics, metamaterial science, electromagnetic (EM) engineering, telecommunications, and signal processing expertises [1]- [3][7] [8]. As a matter of fact, starting from their early conceptualization as thin metasurfaces able to manipulate the wave propagation beyond Snell's laws [11], EMSs are considered as one of the key enabling factors of the revolutionary Smart EM Environment (SEME) paradigm in wireless communications [4]- [6][12] [13].…”

“…Within such a framework, the design of planar artificial materials with advanced propagation management capabilities has been recently demonstrated for static passive EM skins (SP-EMS) by exploiting artificial intelligence (AI) techniques within the System-by-Design (SbD) paradigm [5][6] [15]. Such an approach leverages on the decomposition of the problem at hand into a source design phase and a subsequent optimization of the surface descriptors of the SP-EMS within the Generalized Sheet Transition Condition (GSTC) framework [5] [6] [11]. Thanks to the modularity of such a synthesis tool and its multi-scale-oriented nature, the efficient de-sign of wide-aperture EMSs that enable advanced pattern shaping properties has been carried out [5] [6] despite the use of extremely simple unit cells.…”

“…Such an approach leverages on the decomposition of the problem at hand into a source design phase and a subsequent optimization of the surface descriptors of the SP-EMS within the Generalized Sheet Transition Condition (GSTC) framework [5] [6] [11]. Thanks to the modularity of such a synthesis tool and its multi-scale-oriented nature, the efficient de-sign of wide-aperture EMSs that enable advanced pattern shaping properties has been carried out [5] [6] despite the use of extremely simple unit cells.…”

“…From an applicative viewpoint, the implementation of a continuous control on each RP-EMS cell can yield to very expensive and complex architectures, thus it is generally avoided [19] and the RP-EMS analog states are often discretized using few bits, B, per cell [9] [19] or they are implemented by using binary switches [18]. Therefore, RP-EMSs are usually digitally-controlled systems [18]- [20] with relatively limited per-cell degrees-offreedom (DoFs) when compared to SP-EMSs [5] [6]. A key consequence of such a per-cell constraint, mainly when low-bit (B → 1) RP-EMS are at hand [19], turns out to be the very limited control of the shape of the reflected beam [19].…”

“…However, demonstrating more advanced footprint control/shaping with a digital RP-EMS would be of great interest in practice since it would allow one to efficiently concentrate the reflected power in arbitrary desired areas (i.e., roads, squares, streets, buildings) and not just in spots. Unfortunately, the approach derived in [5] [6] to design SP-EMSs affording shaped footprint patterns cannot be directly applied to RP-EMSs [5] [6]. Indeed, the synthesis of the reference surface current, which is performed in the first step of [5] [6] and that exploits the non-uniqueness of the associated inverse source (IS) problem to take advantage of the non-radiating currents (NRCs) [5] [21], assumes that the unit cell of the corresponding EMS allows a fine tuning of the reflection phase [5] [6].…”