Compact ultra-wideband dielectric resonator antennas

Abstract

UWB communication systems were newly regenerated when the Federal Communications Commission (FCC) defined the 3.1-10.6 GHz unlicensed band for UWB applications. Based on an investigation in designing UWB antennas, researchers have encountered more difficulties compared to a narrow band antenna. UWBantennas should have extremely wide impedance bandwidth while preserving high radiation efficiency with compact size. In some cases, a band-notched function should have been created to avoid electromagnetic interference between nearby existing systems and UWB systems. In this research, various promising UWB Dielectric Resonator Antennas (DRAs) have been demonstrated to overcome several challenges. The impedance bandwidth of the UWB DRAs has been improved for more than 110% by using some techniques such as connecting a strip to the ground plane and modifying structure of Dielectric Resonator (DR). The efficiency issue of UWB antennas is overcome by implementing DR as a resonator element which is excited by various shape structures feed lines to achieve more than 90% efficiency. The electromagnetic interferences between UWB systems and nearby existing systems in the frequency bands of 3.22-4.06 GHz, 4.84-5.96 GHz and 5.71-6.32 GHz are eliminated by using a stub connected to the hollow centre of feed line, an inverted-T shape parasitic strip near DR and modified metallic sheet underneath the DR, respectively. Compared with UWB monopole antennas, UWB DRAs obviate the problem of radiation pattern by utilizing dielectric resonator characteristics. In parallel, the broadside radiation pattern is obtained by implementing various shapes of microstrip feed line at a proper location to excite the DRA that provides symmetry radiation patterns with a consistent stability across the desired bandwidth.