# A Wideband Circularly Polarized Antenna with a Multiple-Circular-Sector Dielectric Resonator
## 3 Experimental Results and Discussion  
Based on the optimized design parameters listed in Table 1, a prototype of the proposed antenna was fabricated. A 99.5% alumina ceramic material with a dielectric constant of 9.8 and a loss tangent of 0.0001 was utilized to fabricate the proposed DR. Figure 7 shows a photograph of the fabricated antenna. Epoxy adhesive was used to glue the bottom layer of the multiple-circular-sector DR to the ground plane. An Agilent 8510C network analyzer was used to measure the reflection coefficient of the fabricated antenna. The measured and simulated results of the reflection coefficients are illustrated in Figure 8. Good agreement between the measurement and simulation results was achieved. It was found that the measured and simulated \(-10\) dB reflection bandwidths were 31.39% (1.88-2.58 GHz) and 29.33% (1.91-2.58 GHz), respectively. Figure 8: Measured and simulated reflection coefficients. Figure 7: Photograph of the fabricated antenna. For the measurement of the radiation characteristics of the proposed antenna, a dual-polarized rectangular horn antenna in a RF anechoic chamber was utilized. The measured and simulated results of the ARs and LHCP gains of the proposed antenna in the broadside direction (\(\theta\) = 0\({}^{\circ}\)) are shown in Figure 9. As can be observed in Figure 9, the measured and simulated 3 dB AR bandwidths were 19.30% (2.06-2.50 GHz) and 21.17% (2.07-2.56 GHz), respectively. Within the measured 3 dB AR bandwidth, a measured peak LHCP gain of 7.65 dBic at 2.225 GHz and gain variation of less than 2.70 dBic were achieved, as shown in Figure 9. Reasonable agreement was noted between the measured and simulated results, with some discrepancies mainly attributed to experimental tolerances, fabrication imperfections, and the existence of a slight air gap between the DR layer and the ground plane during the gluing process, as discussed in Figure 6.  
Figure 10 plots the measured and simulated radiation patterns of the proposed antenna on the \(xz\)-plane (\(\phi\) = 0\({}^{\circ}\)) and \(yz\)-plane (\(\phi\) = 90\({}^{\circ}\)) at the three frequencies of 2.1 GHz, 2.3 GHz, and 2.5 GHz. It is evident that the proposed antenna is an LHCP antenna, and that the radiation patterns are directional toward the broadside direction. In addition, on both planes, the LHCP gains are 20.30 dB, 20.38 dB, and 14.50 dB higher than the right-handed circular polarization (RHCP) gains in the broadside direction at these three corresponding frequencies. The deterioration of the radiation patterns is due to the asymmetry of the proposed DR configuration along the x-axis and y-axis. This effect becomes stronger at higher frequencies. Figure 9: Measured and simulated results of: (**a**) Axial ratios; (**b**) Left-handed circular polarization (LHCP) gains. In order to evaluate the performance of the antenna, a comparison of the proposed antenna and antennas presented in earlier works [11; 12; 13; 14; 15] was performed. These results are illustrated in Table 2. It is evident that the proposed antenna exhibits a wider 3 dB AR bandwidth and a higher peak gain compared to the earlier antennas [11; 13]. Two antennas [12; 14] produced a wider 3 dB AR bandwidths, but their peak gains were lower than that of the proposed antenna. Another antenna [15] employed a trapezoidal DR with overall dimensions of \(1.16\lambda_{0}\times 1.16\lambda_{0}\times 0.44\lambda_{0}\) (\(\lambda_{0}\) is the wavelength corresponding to the center frequency of the AR band). Meanwhile, the overall dimensions of the proposed antenna were only \(0.84\lambda_{0}\times 0.84\lambda_{0}\times 0.39\lambda_{0}\). Therefore, compared to antennas presented in earlier works, the proposed antenna exhibits good performance in terms of antenna gain and 3 dB AR bandwidth, as well as small size. Figure 10: Measured and simulated radiation patterns of the proposed antenna at: (**a**) 2.1 GHz; (**b**) 2.3 GHz; (**c**) 2.5 GHz. RHCP: Right-handed circular polarization.