Implementation of a superdirective dielectric resonator antenna with a symmetrical electric dipole feed

This paper presents an experimental demonstration of superdirective spherical dielectric antennas smaller than a wavelength and having a high overall efficiency. The antennas are designed for 2.4 GHz but can be scaled to other radio frequencies. The proposed antennas with a size less than a wavelength exceed the Kildal limit, have a directivity from 6 to 10 with a total efficiency of at least 80% at a bandwidth of 10-20 MHz. Such high directivities are obtained by constructive interference of the electric TM
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and magnetic TE
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modes of an open spherical resonator. Theoretical models yielding higher directivity and total efficiency are also presented, and ways to improve them further are discussed. The experimental results are in excellent agreement with numerical simulations. Features of various dipole designs and multiport measurements, which are important for antennae implementation are discussed. Additionally we provide a comparison of the obtained directivities with those ones of other known antennas, and analyze spherical, spheroidal and cylindrical geometries excited by a point electric dipole.