Multifunctional passive metacrystals for enhancing wireless communications

Abstract: Intelligent surfaces have emerged as a promising solution to enhance coverage and mitigate signal fading in future wireless communication systems, thereby improving bandwidth and data rates. Passive intelligent surfaces, in particular, demonstrate significant potential for reducing both energy consumption and operational costs. However, their current functionalities are typically constrained to operation within a single polarization, frequency band, and angle of arrival, limiting their applicability in realistic scenarios. In this work, we introduce volumetric dielectric composites, referred to as metacrystals, which are designed through computer optimization to greatly extend the capabilities of intelligent surfaces. Owing to their three-dimensional geometry, which supports a large number of degrees of freedom, metacrystals can simultaneously provide complex multiplexing responses for multiple signals. Each signal can be characterized by distinct parameters, including polarization, angle of incidence, frequency, and/or orbital angular momentum. The proposed metacrystals feature binarized permittivity contrast between low-permittivity materials and air gaps, and can thus be fabricated using filament-based additive manufacturing, supporting frequencies up to 100 GHz. By being cost-effective and scalable, these structures are well-suited for industrial applications, such as integration into building walls, where they can redirect or absorb signals in both indoor and outdoor environments with high versatility at millimeter-wave frequencies and beyond.