In this paper, we present electromagnetic signal and information theory (ESIT). ESIT is an interdisciplinary scientific discipline, which amalgamates electromagnetic theory, signal processing theory, and information theory. ESIT is aimed at studying and designing physically consistent communication schemes for the transmission and processing of information in communication networks. In simple terms, ESIT can be defined as physics-aware information theory and signal processing for communications. We consider three relevant problems in contemporary communication theory, and we show how they can be tackled under the lenses of ESIT. Specifically, we focus on (i) the theoretical and practical motivations behind antenna designs based on subwavelength radiating elements and interdistances; (ii) the modeling and role played by the electromagnetic mutual coupling, and the appropriateness of multiport network theory for modeling it; and (iii) the analytical tools for unveiling the performance limits and realizing spatial multiplexing in near field, line-of-sight, channels. To exemplify the role played by ESIT and the need for electromagnetic consistency, we consider case studies related to reconfigurable intelligent surfaces and holographic surfaces, and we highlight the inconsistencies of widely utilized communication models, as opposed to communication models that originate from first electromagnetic principles.

翻译：本文提出电磁信号与信息理论（ESIT）。ESIT是一门融合电磁理论、信号处理理论与信息理论的交叉学科，旨在研究与设计通信网络中信息传输与处理的物理一致性通信方案。简言之，ESIT可定义为面向通信的物理感知信息理论与信号处理。我们探讨了当代通信理论中的三个相关问题，并展示了如何通过ESIT视角予以解决。具体聚焦于：（i）基于亚波长辐射单元间距的天线设计的理论与工程动机；（ii）电磁互耦的建模机理及其作用，以及多端口网络理论对其建模的适用性；（iii）揭示近场视距信道性能极限并实现空间复用分析的工具。为阐明ESIT的作用及电磁一致性的必要性，我们选取可重构智能表面与全息表面作为案例，指出广泛使用的通信模型相较于基于第一性电磁原理建立的通信模型所存在的非一致性。