## 4 Measurement Results  
The optimized 5G NR band circularly polarized antenna was finally fabricated to measure the experimental results. The photographs of the proposed prototype are presented in Figure 11. The closeup, front view, top view, and back view of the antenna are depicted in Figure 11a-d, respectively. The ECCOSTOCK HiK with permittivity, \(\epsilon_{r}=10\) having loss tangent (\(\$\)) of 0.002 was used as DR material. An 80 \(\times\) 80 mm aluminum ground plane was used. The feeding strip was cut from adhesive copper tape to easily stick to the surface of the DRA. An SMA was soldered at the feed point at the center of the DRA with the feeding strip. S\({}_{11}\) was measured using a vector network analyzer (VNA), while far-field parameters were measured in the anechoic chamber. A 50-\(\Omega\) coaxial cable was used to connect the SMA with the VNA. Double-sided copper tape was used to stick the DRA on the aluminum ground plane] to remove the possible air gap, according to the procedure explained in [26]. The resonant mode frequencies of the RDRA could be predicted using mathematical equations of the dielectric waveguide model, as explained in [27]. According to DWM TE\({}_{813}^{x}\) was estimated at 3.89 GHz and TE\({}_{181}^{y}\) at 4.53 GHz. The comparison between simulated and measured S\({}_{11}\) of the CP DRA is presented in Figure 12. TE\({}_{813}^{x}\) was simulated at 4.13 GHz and measured at 4.12 GHz while TE\({}_{183}^{y}\) was simulated at 4.52 GHz and measured at 4.51 GHz. A close comparison was observed between predicted, simulated, and measured values. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Antenna**} & \multirow{2}{*}{**Geometry**} & \multirow{2}{*}{**No of Strips**} & **10-dB S\({}_{11}\)** & **3-dB AR** & **Polarization** & **5G NR n79 Coverage** \\  & & & **Bandwidth (\%)** & **Bandwidth (\%)** & **(4.4–4.8 GHz)** \\ \hline Geometry 1 & & 1 & Nil & Nil & Linear & NO \\ \hline Geometry 2 & & 2 & Nil & Nil & Circular & NO \\ \hline Geometry 3 & & 3 & Nil & 2 & Circular & NO \\ \hline Geometry 4 & & 4 & 8.8 & 5.8 & Circular & NO \\ \hline Proposed CP & & **5** & **17** & **10** & **Circular** & **YES** \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Performance comparison of different geometries in the development of the CP 5G RDRA. Figure 10: The surface current distribution at the novel feed of the CP 5G RDR. (**a**) At 0\({}^{o}\); (**b**) At 90\({}^{o}\). The comparison of these values is presented ed in Table 3. The impedance matching bandwidth (\(\left|\text{S}_{11}\right|\leq 10\) dB) expanded from 4.05-4.81 GHz in simulation and 4.01-4.83 GHz in measurement. The antenna provided a measured S\({}_{11}\) over a bandwidth of \(\sim\)17%. A small marginal difference between simulation and measurement was observed, due to cable losses and measurement errors. Figure 11: The geometry of the Proposed CP 5G RDRA Photograph of the prototype of the CP 5G RDRA. (**a**) Closeup; (**b**) Front View; (**c**) Top view; (**d**) Back view. Figure 12: Simulated and measured S11 of the CP 5G RDRA. Figure 13 shows the simulated and measured CP response of the proposed RDRA in the boresight direction (i.e., \(\theta=0\lx@math@degree\), \(\Phi=0\lx@math@degree\)). As presented, the axial ratio extended from 4.4-4.84 GHz in simulation, while 4.38-4.82 GHz was measured during the experiment. Circular polarization of bandwidth of \(\sim\)10% was achieved, both in simulation and measurement. The minimum AR value was simulated at 4.44 GHz and measured at 4.43 GHz with a magnitude of 1.92 dB and 1.4 dB, respectively. The negligible difference between theory and experiment was due to cable losses and measurement imperfections. The successful overlap of S11 and AR bandwidths is depicted in Figure 14. As shown, the overlapped bandwidth was good enough to cover the targeted 5G NR Sub-6 GHz band i.e., n79 (4.4-4.8 GHz). A stable and satisfactory performance was offered by the antenna during the experiment.