2D Non-radiating Sources in Mie Scattering and Inverse Problems

Since the early work on a set of theorems to define a general class of non-radiating currents [1], a growing recent interest has been established towards non-radiating sources as the fundamental mechanism behind invisibility cloaks or as a degree of freedom in the design of antenna elements. By imposing the zeros of the external scattered fields, a unified theory of non-radiating currents for volumetric devices and surface structures is derived in terms of cylindrical harmonics field series (Mie scattering) and Field Integral Equation formulation (FIE). Analytical formulas and numerical examples for 2D objects beyond the subwavelength limit highlight the novelty of the present work. For Mie Scattering, the concept of Parity-time cloaking is directly generalized for a homogeneous dielectric cylinder with a balanced loss-gain impedance metasurface cloak, investigating the relation between the number of cylindrical harmonics M to be suppressed and the complexity of a thin surface cloak. For the FIE formulation, non-radiating sources are analyzed in terms of elementary TM and TE non-radiating sources, modeled as a proper set of equivalent electric and magnetic current configurations.