Surface-Wave Metaprism for Smart Surface Communications

We present a design technique and numerical validation for a surface-wave “metaprism" (MTP) acting as a frequency-dependent anomalous reflector for next generation communications in smart radio environment. This device holds promise for enabling physical layer frequency multiplexing and addressing waves in radio blind-spots. The proposed MTP is constituted by a passive and non-reconfigurable metasurface (MTS) comprising three sections. The first section (receiver) operates with low dispersion, receiving broadband signals coming from the base transceiver station (BTS) at a predefined angle and converting them into surface waves (SW). The subsequent transition section gradually increases the dispersion of SW, guiding it towards the highly dispersive transmitter section, which finally converts the SW into space waves radiated towards frequency-dependent angular directions. The latter property motivates the name “metaprism". The MTP is implemented by an array of sub-wavelength metallic patches printed on a grounded dielectric slab, initially modeled using a homogenized penetrable impedance boundary condition (PIBC). The dispersion analysis of the MTS unit cell reveals the impact of patch geometry on dispersion characteristics, which is important for achieving broad scanning performance. Full-wave simulations validate the design, demonstrating high power conversion efficiency and a reasonable frequency scan range. Moreover, the study compares the performance of SW-based MTP with that of a spatially dispersive reflecting intelligent surface (RIS), highlighting the advantages of the MTP. Additionally, the paper investigates an “around the corner" design, where the SW re-routes the signal around a bent transition section, shading light on the relationship between SW dispersion and power loss due to edge-diffraction.