Abstract
An effective and digitally tunable reflective multi-function metasurface in the THz band is proposed. The introduced planar structure consists of an array of a well-designed double-split SRR (DSSRR) utilizing phase-change materials (PCMs) in the gap regions, leading to the controllable function of the metasurface due to the tuning of the crystallization level of PCMs. According to Pancharatnam-Berry's principle, this effect creates different electromagnetic responses only by employing two types of unit cells (bit-0 and bit-1) based on the proper addressing of the PCMs in the structure. It is reported that by digitally changing the coding sequence of the metasurface, it is individually capable of performing different functions such as polarization rotation, beam steering, and RCS reduction. The computational results have been verified by appropriate analytical equivalent electric-circuit modeling and the theory of antenna-arrays. The studied planar-structure with its tunable and coding properties might be suggested for advanced applications in THz sensing, communications, and imaging systems.