Electromagnetic Information Characterizations for Information Metasurface Systems

Electromagnetic (EM) fields reflect the spatio-temporal characteristics of information as its carrier. Analyzing information parameters under EM theory to interpret spatial properties has received attention in recent years. In this paper, we proposed an approach for analyzing EM information characteristics of information metasurface systems by applying principles of electromagnetics. The designed system takes a coded information metasurface with a probability distribution of each coding pattern as the source. And the receiver measures far-fields in free space at given positions. A Fourier transform (FT) method is applied to evaluate the scattering far fields. The posterior probabilities under each receiving scattering field are obtained based on Bayes’ theorem. Parameters including entropy, non-average mutual information (NAMI) and average mutual information (AMI) are then obtained from the posterior probabilities. Channel capacity is then derived from AMI, and its influencing factors are analyzed. Furthermore, field correlation information parameters in the far fields are proposed to analyze the correlation degree, from which the mutual information of joint observation is then analyzed. The proposed method provides references for analyzing information metasurface systems like the emergent direct digital modulation (DDM) system with strong application potentials. This method can also be readily extended to other electromagnetic information systems.