Electrically small antennas embedded in metamaterials: Closed-form analysis and physical insight

The main goal of this work is to understand the behavior of electrically small antennas embedded in metamaterials. To do so, the Green's function for small-size antenna located in small-size metamaterial sphere is approximated, then by applying the method of moment with Galerkin's procedure the probe current and input impedance as a function of sphere radius, antenna length, and material properties are derived. The results clearly demonstrate that in most of the designs considering the first dominant mode is not sufficient and one needs to consider higher order terms in Green's function expansion to provide an accurate analysis for antenna performance. A physical insight is highlighted.