Concept, realization, and applications of coding metasurfaces

Coding metasurfaces, characterized by processing the electromagnetic waves for specified functions through predesigned coding sequences either in space or time, can manipulate the electromagnetic waves in both space frequencies and time frequencies. They have been emerging as the revolutionary platforms for metasurface technologies in recent years. In this paper, we first introduce the general concept and operating principle of the coding metasurfaces. Then, two design strategies for realizing the coding metasurface particles, altering resonant states and switching current phase, are provided, respectively. Next, two recent reported applications that are based on space-coding metasurface for RCS reduction and time-coding metasurface for spread-spectrum wireless communication are presented, respectively. Finally, existing challenges and potential future research directions in coding metasurfaces are discussed.