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In this article, we review recent advances in static and reconfigurable Huygens’ metasurfaces (HMSs) for antenna beamforming and beam steering. First, the fundamental theory of HMSs is summarized along with basic approaches for their physical realization. Subsequently, precise antenna beamforming without feeding networks by utilizing static HMSs is described. This is followed by the description of using HMSs as radomes for extending the scan range of phased arrays. Finally, several strategies are described for realizing reconfigurable HMS by means of electronic control devices. [ABSTRACT FROM AUTHOR]

An accurate equivalent circuit model (ECM) for general multiwire multiorder printed circuit board (PCB) metagratings (MGs) is developed. The effective impedances of the grating wires are modeled as lumped loads in the ECM. The numerous propagating Floquet harmonics supported by the grating are modeled as circuit ports. Based on the desired field transformation for the MG, a set of required scattering parameters for its ECM is derived. The equivalent lumped loads are subsequently optimized to realize these parameters, which is analogous to shaping the diffraction pattern of the MG to match the desired functionality. Within this framework, it is possible to encode multiple functions into a single device by simultaneously optimizing all relevant entries of the ECM scattering matrix. Using the proposed technique, an angle-multiplexed multifunctional MG is designed and investigated. [ABSTRACT FROM AUTHOR]

A new topology for Huygens’ metasurfaces (HMSs) is proposed as a means for dramatically simplifying the design of metasurface-based devices. Traditionally, the constituent unit cells for such metasurfaces are designed and optimized with many assumptions such as local periodicity, normal incident rectilinearly propagating excitation, etc. For applications demanding precise wave transformation, it is necessary to further optimize all the cells collectively to compensate for the inaccuracies of these assumptions. For complex designs with many degrees of freedom, this can be extremely time-consuming. In this paper, we propose a new unit cell topology, which intrinsically enforces the aforementioned assumptions, enabling rapid construction of metasurfaces from a library of preoptimized cells without the need for any subsequent tuning. To illustrate the effectiveness of the proposed topology, several devices are designed and verified numerically. For practical demonstration, a wide-angle reflectionless refracting metasurface employing the proposed unit cells is fabricated and experimentally tested. [ABSTRACT FROM AUTHOR]