Sub-THz Spatially Modulated Beam Splitting Reflectors for Potential RIS Implementations

Reconfigurable intelligent surfaces (RISs) promise to revolutionize wireless communications by creating a smart electromagnetic environment. They facilitate beamsplitting and beamsteering of EM waves in sub-THz communications. It's worth noting that implementing Reflective Intelligent Surfaces (RIS) in this high band using conventional concepts, such as metasurfaces or reflectarrays, requires individual control of elements or groups of elements, increasing fabrication complexity. In this study, we present a spatially modulated RIS concept, demonstrating its potential as a reconfigurable beam splitter. The proposed structures are first theoretically designed using theoretical calculations, followed by simulations and experimental validations. Unlike the traditional reflectors, this structure can manipulate sub-THz beams with a very simple reconfiguration, making it highly promising for dynamic sub-THz RIS implementation. By adjusting only the element spacing, it can split a 150 GHz normal incident wave into multiple beams at varying reflection angles. Such multi-beam control capability in reflectors promises a potential pathway towards enabling RISs in future joint communications and sensing systems.