Performance Analysis of Dipole Antennas Embedded in Core-Shell Spheres: A Green's Function Analysis

TL;DR

This paper theoretically investigates how embedding a dipole antenna in a core-shell sphere with magnetic and dielectric materials can achieve high bandwidths and low Q factors close to the Chu limit, using Green's function and MoM analysis.

Contribution

It introduces a Green's function based method to analyze the input impedance and bandwidth of embedded dipole antennas in core-shell structures, demonstrating near-Chu limit performance.

Findings

Embedding in magnetic shell reduces Q factor.

Core-shell structure enhances bandwidth.

Resonator approaches Chu limit.

Abstract

The main goal of this work is to theoretically investigate the behavior of an electrically small antenna enclosed in a concentric sphere. The Greens function analysis is applied to characterize the input impedance of a concentric resonator excited by a dipole located at its center. The method of moments (MoM) with Galrekin's procedure is used to determine the current distribution over the source excitation and hence the input impedance. The behavior of quality factor (Q) and bandwidths of the antenna is studied with the use of input impedance as a function of frequency. We illustrate that by embedding a dipole antenna inside a core-shell structure, with magnetic shell and dielectric core, a Q as low as the Chu limit can be approached. The obtained observations demonstrate how a resonator composed of magnetic shells can provide electrically small antennas with high bandwidths performance.