Essential Maintenance: All Authorea-powered sites will be offline 9am-10am EDT Tuesday 28 May
and 11pm-1am EDT Tuesday 28-Wednesday 29 May. We apologise for any inconvenience.

loading page

A Theory for Electromagnetic Radiation and Coupling
  • Gaobiao Xiao
Gaobiao Xiao
Shanghai Jiaotong University, Shanghai Jiaotong University, Shanghai Jiaotong University, Shanghai Jiaotong University, Shanghai Jiaotong University

Corresponding Author:[email protected]

Author Profile


A theory for analyzing the radiative and reactive electromagnetic energies of a radiator in vacuum is presented. In vacuum, the radiative electromagnetic energies will depart from their sources and travel to infinity, generating a power flux in the space. However, the reactive electromagnetic energies are bounded to their sources. They appear and disappear almost in the same time with their sources, and their fluctuation also causes a power flux in the space. In the proposed theory, the reactive electromagnetic energies of a radiator are defined by postulating that they have properties similar to the self-energies in the charged particle theory. More importantly, in addition to a main term of source-potential products, the reactive energies contain a special energy term which will last to exist a short time after the sources disappear. This oscillating energy is related to the electric displacement and the vector potential, and seems to be responsible for energy exchanging between the reactive energy and the radiative energy in the radiation process, performing like the Schott energy term. As the Poynting vector describes the total power flux density related to the total electromagnetic energy, it should include the contributions of the propagation of the radiative energies and the fluctuation of the reactive energies. The mutual electromagnetic couplings between two radiators are also defined in a similar way in which the vector potential plays a central role. The reactive electromagnetic energies can be evaluated with explicit expressions in time domain and frequency domain. The theory is verified with the Hertzian dipole and numerical examples.
25 Sep 2023Published in Electronics volume 12 issue 19 on pages 4031. 10.3390/electronics12194031