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Electrically Small Huygens Dipole Rectennas for Wireless Power Transfer Applications

A series of electrically small Huygens dipole rectennas are reviewed in this paper. Their design concepts rely on the integration of electrically small Huygens dipole antennas with a highly efficient AC-to-DC rectifier circuit. The basic radiating elements of these Huygens systems are two metamaterial-inspired, electrically small, near-field resonant parasitic (NFRP) elements: an Egyptian axe dipole (EAD) and a capacitively-loaded loop (CLL), and a dipole antenna. The AC-to-DC conversion circuit is a full-wave rectifier circuit based on two Schottky diodes and lumped RLC elements. By properly integrating and arranging the NFRP and dipole elements with the rectifier, four rectennas have been developed. They are a low-profile electrically small Huygens linearly-polarized (HLP) rectenna, a low-profile electrically small Huygens circularly-polarized (HCP) rectenna, a dual-functional HLP rectenna and antenna system, and an ultra-thin electrically small HLP rectenna. They are ideal candidates for wireless power transfer applications in 5G Internet-of-Things (IoT) ecosystems.