  In the era of Internet of things, the emerging technologies require new
generation of small form-factor, narrowband, and highly directive antennas to
reduce the interference of radio-frequency waves. Here, on using a stochastic
optimization algorithm combined with a rigorous analytic solution, we show that
the classical directivity limit can be appreciably surpassed for electrically
small dielectric resonant antennas. We provide experimentally feasible designs
of superdirecrtive multilayer spherical antennas excited by a point electric
dipole.
