Experimental demonstration of superdirective spherical dielectric antenna

High directivity of spherical high-index dielectric antennas with an electric dipole excitation is associated with constructive interference of particular electric and magnetic modes of an open spherical resonator at certain frequencies. An experimental demonstration of the directivities exceeding the fundamental Harrington-Chu and Kildal limits -- a phenomenon called superdirectivity -- is provided. We study the performance of such antennas and obtain 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. The demonstrated concept scales to other frequency ranges.