The Off-Shell Electromagnetic T-matrix: momentum-dependent scattering from spherical inclusions with both dielectric and magnetic contrast

Polarization of Charged Spherical Dielectric Core-Shell

Two point charges are placed in a spherical dielectric core-shell embedded in a dielectric environment, one of the charges being located in the core and the other in the shell. The core, shell, and environment are characterized by different dielectric constants. Analytical solutions for the electrostatic energy of the system and the polarization charge density at the core-shell and shell-environment interfaces are obtained by a classical approach.

Ultracompact all-dielectric superdirective antennas

We demonstrate a simple way to achieve superdirectivity of electrically small antennas based on a spherical dielectric particle with a notch. We predict this effect theoretically for nanoantennas excited by a point-like emitter located in the notch, and then confirm it experimentally at microwaves for a ceramic sphere excited by a small wire dipole. We explain the effect of superdirectivity by the resonant excitation of high-order multipole modes of electric and magnetic fields which are usually negligible for small perfect spherical particles.

Dielectric Screening in a Spherical Cavity

In this work we examine the electrostatic screening potential due to a point charge located off-centre in a spherical dielectric cavity. This potential is expanded for the case in which the dielectric constant $ε$ is large, several methods of finding the terms in the expansion are investigated, and closed-form expressions are found through third order in $ε$ along with error bounds. Finally, possible uses of these expressions in molecular dynamics simulations of isolated charged molecules is discussed.

超定向球形介质天线的实验演示

Experimental demonstration of superdirective spherical dielectric antenna

本文实验演示了球形高折射率介质天线突破 Kildal 极限的超定向性，在三分之一波长尺寸下实现约10的定向性和超过80%的效率，并验证了仿真与实验的高度一致。

Size-Dependent Bruggeman Approach for Dielectric-Magnetic Composite Materials

Expressions arising from the Bruggeman approach for the homogenization of dielectric-magnetic composite materials, without ignoring the sizes of the spherical particles, are presented. These expressions exhibit the proper limit behavior. The incorporation of size dependence is directly responsible for the emergence of dielectric-magnetic coupling in the estimated relative permittivity and permeability of the homogenized composite material.

Magneto-Dielectric Substrates in Antenna Miniaturization: Potential and Limitations

In the present paper we discuss antenna miniaturization using magneto-dielectric substrates. Recent results found in the literature reveal that advantages over conventional dielectric substrates can only be achieved if natural magnetic inclusions are embedded into the substrate. This observation is revised and the physical background is clarified. We present a detailed discussion concerning magnetic materials available in the microwave regime and containing natural magnetic constituents. The effects of magnetic dispersion and loss are studied: constraints on the microwave permeability are used…