A New Technique for the Analysis of Energy Coupling and Exchange in General Antenna Systems

This paper provides a deeper insight into the nature of electromagnetic interactions by studying practical settings of strong and weak mutual coupling involving typical antenna elements coupled through the near field. We develop new techniques capable of analyzing the dynamic structure of generic antenna-antenna interactions by describing how energy exchange is divided between propagating and nonpropagating parts in a way reflecting the geometrical shapes and interelement distances of the coupled antennas. The proposed method is implemented through a special method-of-moment (MoM) numerical model and is used to give information about how energy is localized between antennas or electromagnetic objects, which is directly related to the physics of complex systems and the problem of energy storage, transfer, and manipulations. The work utilizes some recent developments in which a spectral near-field theory and the antenna current Green's function formalism were proposed to analyze and describe general electromagnetic systems. The present formulation is developed in conjunction with the special MoM implementation to generate various numerical illustrations and new field energy density pictures combined with analysis of the physics of near-field coupling as revealed through the new results. The technique realized here can be easily integrated into existing full-wave solvers such as MoM to provide systematic pictures of near-field interactions and coupling with more comprehensive and detailed information compared with conventional port parameters such as the S-matrix. The method is suitable for applications such as near-field detection, energy transfer, and near-field communications, besides its fundamental importance for mutual coupling in antenna arrays in general.