# A Two-Port Dual-Band Dual-Circularly-Polarized Dielectric Resonator Antenna
## 3 Experimental Results and Discussion  
To corroborate the simulated results, an antenna prototype based on the optimal parameters was made and tested. A picture of the fabricated prototype is shown in Figure 11a. The DR was made of an alumina (\(Al_{2}O_{3}\)) ceramic material having a dielectric constant of 10 and a loss tangent of 0.0001. This material has high stability and excellent mechanical properties such as outstanding strength, hardness, heat insulation, oxidation resistance, corrosion resistance, and high-temperature capability [23]. At the same time, the high coefficient of thermal expansion (CTE) (\(\alpha_{20-1000^{\circ}\mathrm{C}}=8\times 10^{-6}\) K\({}^{-1}\)) helps minimize the expansion at elevated temperatures to avoid manufacturing tolerances [24]. Therefore, alumina ceramic materials are compatible with computer numerical control (CNC) machining. In addition, with the advancement of current technology, we can completely control and adjust the temperature during the machining process to be compatible with each specific material, ensuring the accuracy of the processed prototype. A specific-shaped prototype of the main DR is set up with computer-aided design (CAD) software version 23.0, and then fed into a CNC milling system. The milling process will be programmed to operate automatically to accurately remove each part that needs to be cut from the workpiece. The milling machine will include three main axes to position and move the DR workpiece to be machined to different positions along the 3 axes X, Y, and Z. Combined with two 360\({}^{\circ}\) rotation axes to machine and cut corners, slots, and grooves of any shape and position on the DR workpiece. Based on the geometric structure of the main DR in this study, the first step is to cut the workpiece into a cube with dimensions \(a_{2}\times a_{3}\times(d_{1}+d_{2})\). Next, two opposite truncated diagonal corners of the cube with side length \(b\) and height \((d_{1}+d_{2}-d_{3})\) are cut out from the main DR. After that, the four diagonal corners below the DR are removed to form the cross-shaped DR. Finally, two diagonal grooves at the bottom and one longitudinal groove at the top are cut out of the DR workpiece. The ground plane and the microstrip feedline are mounted on the top and bottom layers of a Taconic TLY-5 dielectric substrate with a dielectric constant \(\varepsilon_{r}\) = 2.2, a loss tangent tan\(\delta\) = 0.0009, and a thickness of 0.76 mm. The ground plane is 41 mm \(\times\) 41 mm in size. The fabricated DR was attached to the ground plane using epoxy glue. Two  
Figure 10: Simulated results of (**a**) reflection coefficient, (**b**) AR when P1 excited and (**c**) AR when P2 excited for the proposed DBDCP in terms of \(w_{sub}\). SMA connectors were used for the experiment. The inner pins of the SMA connectors are soldered to the feedlines. An Anritsu MS46122B vector network analyzer was utilized to attain the \(S\)-parameters characteristic of the proposed DRA, whereas the radiation properties, such as gains, ARs, and radiation patterns, were measured inside a small RF anechoic chamber in which a dual-band polarized horn antenna was utilized, as shown in Figure 11b. The horn antenna is mounted at the far-field tower and connected to a spectrum analyzer to test and measure the radiation pattern of the antenna under test. The radiation pattern is measured at each 1\({}^{\circ}\) step interval in the anechoic chamber with a range of 0-360\({}^{\circ}\), over an operating frequency band of 3.0-6.5 GHz with each frequency step being 0.25 GHz. Figure 12 depicts a comparison of the measured and simulated \(S\)-parameters of the proposed two-port DBDCP DRA. Good agreement is achieved between the measured and simulated results. When P1 is excited, the antenna operates at the LB with a \(-\)10 dB IBW of 3.35-4.42 GHz (27.5%) in simulation and a \(-\)10 dB IBW of 3.52-4.5 GHz (24.4%) in measurement.