A Low-Profile Multilayer Cylindrical Segment Fractal Dielectric Resonator Antenna: Usage for wideband applications

Until the 1980s, shielded dielectric resonators (DRs) were used as high-quality factor energy storage devices for filter and oscillator applications [1]. Later, they gained status as effective radiators due to the efforts of Long, McAllister, and Chen [2]. Since then, enormous DR antenna (DRA) designs have been explored and different feeding techniques introduced to achieve optimum antenna characteristics like high gain and low quality factor (Q-factor), etc. Compared to microstrip antennas, DRAs offer attractive features such as low loss, high efficiency, and wide impedance bandwidth (BW). Low-profile design and BW enhancement are two important aspects of effective antenna synthesis. Various BW enhancement techniques-like the compact slot DRA [3], aperture feeding, perturbation, cavity-backed disk, ring-shaped DRA, and the stacking of two or more dielectric layers [4]-can be applied on DRAs for this purpose. The stacked DRA, dual-segment, hybrid DRA, and slots in ground-plane approaches were also well suited to improve the impedance BW of DRA [5]-[10]. Various multilayer cylindrical DRA (MCDRA) structures have been proposed and investigated for BW enhancement like the stacked cylinder approach [11], [12], slotted coaxial layered structure [13], etc. More recently, various fractal geometries have been introduced for antenna applications. The main objective of fractal applications is to reduce the size of the antenna for wideband characteristics, while maintaining other design parameters at an acceptable level. Several antenna configurations based on fractal geometries have been previously examined [14].