Experimental demonstration of superdirective spherical dielectric antenna

TL;DR

This paper experimentally demonstrates superdirective spherical dielectric antennas exceeding the fundamental limit, achieving high directivity and efficiency with a small size, suitable for high-frequency applications like 5G and IoT.

Contribution

It provides the first experimental validation of superdirective dielectric antennas with directivities beyond the Kildal limit, using high-index ceramics for size reduction.

Findings

Achieved directivity factor of about 10 with over 80% efficiency.

Constructive interference of electric and magnetic modes enhances directivity.

Excellent agreement between experimental measurements and simulations.

Abstract

An experimental demonstration of directivities exceeding the fundamental Kildal limit, a phenomenon called superdirectivity, is provided for spherical high-index dielectric antennas with an electric dipole excitation. A directivity factor of about 10 with a total efficiency of more than 80\% for an antenna having a size of a third of the wavelength was measured. High directivities are shown to be associated with constructive interference of particular electric and magnetic modes of an open spherical resonator. Both analytic solution for a point dipole and a full-wave rigorous simulation for a realistic dipole antenna were employed for optimization and analysis, yielding an excellent agreement between experimentally measured and numerically predicted directivities. The use of high-index low-loss ceramics can significantly reduce the physical size of such antennas while maintaining their overall high radiation efficiency. Such antennas can be attractive for various high-frequency applications, such as antennas for the Internet of things, smart city systems, 5G network systems, and others. The demonstrated concept can be scaled in frequency.