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 solutions for a point …