I. Introduction
Electrically small antennas and antenna arrays have been extensively studied for several decades due to their theoretical and practical importance [1]–[6]. As a result of their small electrical size, these antennas and antenna arrays find many applications, including wireless communications, electromagnetic (EM) sensors, small aperture radars, and compact microwave and millimeter-wave imaging systems [1], [6], [7]. Several interesting designs of electrically small antennas have been proposed recently. These include folded antenna geometries [1], [2], [6], [8], metamaterials [9]–[11], dielectric resonator antennas [1], [12], and biologically inspired resonantly loaded antennas [13], [14].