Spatial Maps of Reactive Energy Density around Antenna Arrays: An EM Lagrangian Approach

In this paper, we present an EM Lagrangian based approach to quantify the distribution of reactive energy density around generic antennas, specifically multi-port excited arrays. FDTD-computed electric and magnetic field values are first used to obtain EM Lagrangian density in the antenna near-field, which is further time-averaged to obtain spatial patterns of capacitive/inductive reactive energy density. We demonstrate the significant alterations in reactive energy density distributions for thin-wire dipole based arrays, considering different port-excitation conditions and use of parasitic reflectors/directors.