# A Wideband Circularly Polarized Antenna with a Multiple-Circular-Sector Dielectric Resonator
## 1 Introduction  
With the rapid development of wireless communication systems, the demand for high efficiency, wideband, and compact antennas has increased significantly [1; 2]. Various types of antennas, such as microstrip patch antennas [3; 4] and dielectric resonator antennas (DRAs) [5; 6], have been investigated and developed for wireless communications. However, microstrip patch antennas (known as metallic-based antennas) usually have low radiation efficiency levels, owing to conductor loss. Meanwhile, DRAs, with no conductor loss, offer the advantages of high radiation efficiency, ease of excitation, small size, and wide bandwidth [7; 8]. Therefore, DRAs have become an excellent candidate for use in wireless communication applications.  
DRAs with a diversity of antenna geometries and feeding schemes have been designed for both linearly polarized (LP) and circularly polarized (CP) systems. Compared to LP antennas, CP antennas are more feasible, because they can reduce the losses caused by propagation effects and misalignment between the transmitting and receiving antennas [9]. Thus, the designs of CP DRAs have received much attention recently [10; 11; 12; 13; 14; 15; 16]. The technique for realizing circular polarization through a DRA mostly requires either modifying the excitation mechanism or using a specially-shaped dielectric resonator (DR). CP DRAs with different excitation techniques to excite simple regularly-shaped DRs have been reported. For example, in one study [10], [PERSON] et al. proposed a rectangular DRA excited by concentric open half loops to achieve a 3 dB axial ratio (AR) bandwidth of 14%. [PERSON] et al. introduced a CP DRA fed by a lumped resistively loaded monofilar-spiral slot, resulting in an AR bandwidth of 18.7% [11]. A modified cross-slot design was also utilized to excite a rectangular DRA toproduce circular polarization with an AR bandwidth of 24.6% [12]. Meanwhile, designs of CP DRAs with specially-shaped DRs fed by the aperture-coupled feeding technique were also investigated. In one such study [13], an AR bandwidth of 11.57% was achieved using a Spidron fractal-shaped DR. A CP DRA with a grooved rectangular DR was also presented, reportedly showing an AR bandwidth of 23.75% [14]. [PERSON] et al. introduced a trapezoidal DRA [15] which offered an AR bandwidth of 21.5%. Recently, a CP DRA with an AR bandwidth of 18.2% was realized in a design which used two rectangular DR layers stacked together at a rotating angle relative to adjacent layers [16].  
In this paper, we propose a wideband CP DRA which uses a specially-shaped DR, referred to as a multiple-circular-sector DR. The cylindrical DR was divided into twelve circular-sector DRs having identical central angles of 30\({}^{\circ}\). Circular polarization is achieved in this design by optimizing the radii of the twelve circular-sector DRs using a genetic algorithm (GA), a technique which has been applied to solve many antenna optimization problems [17; 18]. As a result, the proposed antenna exhibits wideband CP characteristics. The proposed antenna was excited by the coupling between a narrow rectangular slot etched on the ground plane and a 50-\(\Omega\) microstrip feeding line located underneath the slot. A simulation was carried out using the ANSYS High-Frequency Structure Simulator (HFSS). An antenna prototype with optimal design parameters was fabricated and tested. This paper is organized as follows. Section 2 introduces the design concept of the proposed antenna. The experimental results and a comparison between measured and simulated results are presented in Section 3. Finally, the conclusion is given in Section 4.