## 2 Proposed Antenna Structure  
### Antenna Design and Configuration  
The proposed wide-band CP monopole antenna with the complete geometrical configuration is shown in Figure 1. FR4 with a total size of 32 \(\times\) 30 \(\times\) 1.6 mm\({}^{3}\) and \(\varepsilon\)r = 4.4, tan \(\delta\) = 0.025 was used as a substrate. The suggested antenna was connected to a 50 \(\Omega\) microstrip feed line with an optimal position to enhance the matching of the antenna. An L-shaped connected to a C-shaped mirror to compose a suggested U-shaped radiator was added to the front side. Moreover, a partial ground plane with two rectangle slots and a quadrilateral-shaped parasitic strip was added to the back side of the substrate. The two rectangle slots were cut from the edge of the ground plane to achieve CP modes at high frequencies. The wide CP generation was achieved by adding a quadrilateral strip to the bottom of the substrate, as illustrated in Figure 1. It was used to create a CP mode at a lower frequency that, in turn, improved the AR over the desired frequency. Table 1 presents the dimensions of the antenna. The suggested structure was passed through four stages to achieve the desired final design. The four-step antenna design procedure is illustrated in Figure 2. In Ant. #1, an L-shaped radiator on the front side with the partial ground on the bottom was designed, as shown in Figure 2. As displayed in Figure 3 (the green curve), the antenna is operated at dual-wide-band ranges. The first started from 3.5 to 5.9 GHz and the second worked from 6.5 up to 10 GHz. To extend the impedance bandwidth to cover the two ranges from 4 up to 9 GHz, as shown in Figure 3 (the red curve), the mirror of a C-shaped radiator was connected to an L-shape to achieve the U-shaped radiator, as shown in Figure 2 (Ant. #2). From the two steps, the desired wide-band operating bandwidth can be achieved; however, the CP behavior is not generated, which is related to AR, as shown in Figure 4. Therefore, to achieve the CP feature, a rectangular part was cut from the two edges of the ground plane as Ant. #3 was introduced to improve the antenna matching, as shown in Figures 2 and 3 (blue curve). Moreover, a CP mode was excited at 5.5 GHz, as shown in Figure 4. The 3 dB AR was operated from 5.2 to 6 GHz. The CP radiation can be obtained by achieving two orthogonal modes with equal amplitudes and a 90\({}^{\circ}\) phase difference. However, the conventional monopole antenna, as shown in Figure 2 (Ant. #1, Ant. #2), has little radiation in the horizontal direction. In addition, the horizontal currents in the ground plane moved in opposite directions; therefore, the horizontal current was annulled, which decayed the horizontal polarization. Therefore, linear vertical polarization was generated, as illustrated in Figure 4. Thus, by modifying the ground plane and adding the parasitic strip, as shown in Figure 2 (Ant. #3, Ant. #4), orthogonal horizontal and vertical currents were produced. Moreover, the direction of the current distribution in the ground plane changed, generating CP and increasing the AR value, which tended to increase the bandwidth of the axial ratio, as shown in Figure 4. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Parameter** & **Length [mm]** & **Parameter** & **Length [mm]** & **Parameter** & **Length [mm]** \\ \hline \(L_{sub}\) & 30 & \(L_{3}\) & 4.5 & \(L_{g}\) & 2.8 \\ \hline \(L_{p}\) & 12 & \(L_{4}\) & 4.45 & \(h\) & 1.6 \\ \hline \(L_{f}\) & 11 & \(L_{5}\) & 5.77 & \(W_{sub}\) & 32 \\ \hline \(L_{1}\) & 3.5 & \(L_{6}\) & 2.5 & \(W_{p}\) & 19.25 \\ \hline \(L_{2}\) & 5.5 & \(L_{gnd}\) & 9 & \(W_{f}\) & 3 \\ \hline \(W_{1}\) & 1.4 & \(W_{3}\) & 6 & \(W_{5}\) & 4.45 \\ \hline \(W_{2}\) & 2.5 & \(W_{4}\) & 5.77 & \(W_{6}\) & 2.5 \\ \hline \(W_{7}\) & 10 & \(d\) & 9.9 & & \\ \hline \end{tabular}
\end{table} 
Table 1: The antenna dimensions. Figure 1: The antenna’s complete geometrical configuration. Finally, in Ant.