Spectral Floquet-spatial modulations devoted to strongly coupled periodic arrays: metasurfaces, dense massive MIMO, reconfigurable-intelligent-surfaces (RIS), 5G and 6G uses

In this paper, we propose a spectral modulation technique with its spatial equivalent to studying the coupled largely finite and infinite periodic arrays, useful for 5G and 6G applications (e.g., reconfigurable smart surfaces for 6G systems). Several forms of spectral and spatial modulations are presented. The sum of these modulations based on their large spatial periods allows the estimation of the total large array response (and to control their beam orientation in any desired direction) in the presence of a large number of elements (e.g., dense massive MIMO). The decomposition into sub-arrays where each of them has its own modulation character is demonstrated based on the Floquet analysis (steering the beam of each modulation zone independently of the other neighboring zones is possible in the same panel structure). Various numerical methods use these modulation properties in their kernels, including the MoMGEC.