Low-Profile ESPAR Using Metamaterial-Inspired Structure

This paper addresses the 3D nature of traditional Electronically Steerable Parasitic Array Radiators (ESPARs). Additionally, the required distance between the main radiator and the parasitic elements usually affects the antenna's electrical size and the frequency bandwidth. To overcome these issues, the cylindrical parasitic elements in conventional ESPARs are replaced with Metamaterial-inspired structures that mimic artificial magnetic conductors (AMC). The AMC is realized by a capacitively loaded loop (CLL). PIN diodes electrically control the CLL's behavior while radially loading a printed loop antenna. Switching ON/OFF the diodes changes the direction of the main lobe, resulting in a compact, single-layer, low-profile, and cost-effective structure. By replacing the PIN diodes with varactors, a dual-band and frequency-reconfigurable ESPAR are designed and implemented, which is not possible in traditional ESPAR structures.