Combining Frequency-Selective Scattering and Specular Reflection Through Phase-Dispersion Tailoring of a Metasurface

Reflective metasurfaces (or meta-mirrors) composed of artificially engineered subwavelength structures provide an alternate paradigm for arbitrarily controlling wave reflection with high efficiency. We introduce the concept of frequency-selective coding of a meta-mirror to perform desired scattering properties in different frequency bands by tailoring the phase dispersion of the metasurface. As a particular example, broadband backward-scattering reduction and high-efficient specular reflection are combined by a single meta-mirror in a frequency-selectivemanner. Twometa-atoms with optimized metallic patterns are used as the binary coding elements to realize an out-of-phase function in two side-bands, while the in-phase function is in the center frequency window. Then, we experimentally demonstrate that polarization-insensitive diffusion-like scatterings can be achieved by the proposed meta-mirror with randomly distributed metaatoms in two side-bands from 7.5 to 9.5 GHz and 11.6 to 15 GHz, while in the selected center frequency window around 10.7 GHz, a high-efficient specular reflection property is realized. The experimental results are in good agreement with the full-wave simulations. Compared with the conventional metasurface designs for scattering reduction, the proposed concept exhibits a frequency-selective effect and hence can be used in many practical applications, for example, working as the ground plane of antennas to enable a high-efficient in-band radiation with out-of-band low-backward scattering.