Electromagnetic Diffraction Interpretation of Periodic Structures and Antennas Based on Asymptotic Analysis of Floquet Modes Decomposition

Periodic structures are popularly applied to form a class of electromagnetic devices, including phase arrays of antennas, frequency selective surfaces (FSS), reconfigurable intelligent surfaces (RIS) regarding reflectarrays and transmitarrays, meta-surfaces, etc. The radiation and scattering mechanisms are crucial to making an effective structural configuration, especially with a physically appealing interpretation. Floquet mode decomposition has been shown to be effective in interpreting electromagnetic (EM) wave propagation or evanescent behaviors. The interpretation can be further enhanced by performing the asymptotic evaluation of the resulting Floquet modes, which gives ray-type solutions. The advantage is that the ray solutions can be identified to provide different radiation, scattering, and diffraction mechanisms. By locally treating each mechanism and applying them to design the periodic structures, one can get a more reliable performance.