Reconfigurable Electrically Small Huygens Dipole Antenna with Full Space Radiation Coverage

Abstract

A reconfigurable, electrically small Huygens dipole antenna (HDA) with full space (quasi-isotropic) radiation coverage is reported. One unique feature of the design is its uniform polarization across the entire space. The HDA consists of two metamaterial-inspired electrically small radiating elements: an Egyptian axe dipole (EAD) and a reconfigurable capacitively loaded loop (CLL), and a small driven dipole. The width of the top strip of the CLL is reconfigured slightly by controlling the on/off states of two PIN diodes located between a thin strip and the CLL. Because the coupling effect between the EAD and CLL is dependent on the width of the top strip of the CLL, the phases of the currents on the EAD can be changed by 180° by varying it. As a result of the Huygens radiation physics, such a phase change alters the radiation pattern between the broadside forward- and back-directed modes. Because of the extremely broad beamwidth of the ensuing Huygens patterns, quasi-isotropic radiation coverage is realized. Furthermore, the length of the short-driven dipole is also reconfigured by one PIN diode to maintain consistent impedance matching at 915 MHz in the ISM band for both modes. It is an ideal candidate for indoor wireless power transfer (WPT) enabled IoT applications.