# Higher-Order-Mode Triple Band Circularly Polarized Rectangular Dielectric Resonator Antenna
## 2 Materials and Methods
### Double stub Feed DR Antenna with Parasitic Patch (DRA3)  
The optimized circularly polarized DRA has been excited in higher-order mode by feeding it with double stub and parasitic patch coupling at optimized lengths and widths, as illustrated in Figure 1. The parasitic patch increases the impedance match of the antenna as well as widening the bandwidth. The final dimension of the proposed antenna is given in Table 1. In the proposed DRA, it is found that both fundamental mode \(\text{TE}^{\text{x}}_{\beta 11}\) and higher-order mode \(\text{TE}^{\text{x}}_{\beta 23}\) were generated. The higher mode \(\text{TE}^{\text{x}}_{\beta 23}\) at 4.9 GHz and 5.4 GHz help in  
Figure 5: The proposed double stub DRA (DRA2).  
Figure 6: Result for a double stub DR antenna (DRA2). (**a**) Reflection coefficient and (**b**) axial ratio.  
enhancing the circularly polarized bandwidth [11] and the gain of the antenna. Moreover, the higher-order mode has been excited using a low-cost, simple excitation mechanism without compromising on the size and shape of the DRA.  
The result showed in Figure 8, where the dotted line gives the optimized design. The antenna resonates at three different frequencies: at 2.88 GHz with an impedance bandwidth of 1.6 GHz (46.24%), 5.2 GHz, and 5.69 GHz with bandwidth 6.3% and 2.5%, respectively. Adding parasitic elements at an optimized distance to the feed strip improved the antenna's impedance matching and resulted in a wider bandwidth and operate in the higher mode, TE\({}_{\theta 23}^{\rm{E}}\). Comparing the optimized design to the previous method can be seen in Figure 8. The final design exhibits better impedance matching and broader bandwidth.  
The intensity of current distribution for the DRA increases as the metal strip is added to the DRA, as illustrated in Figure 9. The proposed DRA exhibits the highest current distribution, which is indicated by the red color. The mode generated is depicted by Figure 10, fundamental mode TE\({}_{\theta 11}^{\rm{S}}\) is excited at 3 GHz and higher mode, TE\({}_{\theta 23}^{\rm{S}}\) excitation at 4.9 GHz and 5.4 GHz.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **Dimension (mm)** & **Parameter** & **Dimension (mm)** \\ \hline B & 25.4 & H\({}_{1}\) & 11 \\ C & 14.3 & H\({}_{2}\) & 10.1 \\ H & 26.1 & b\({}_{1}\) & 7.1 \\  & & b\({}_{2}\) & 5.27 \\ \hline \hline \end{tabular}
\end{table}
Table 1: The optimized DRA dimension.  
Figure 8: The comparison of the reflection coefficient for the proposed DRA.  
Figure 9: Current distribution of the DRA, (**a**) DRA1, (**b**) DRA2 and (**c**) the proposed DRA.  
The variation of AR as a function of elevation angle is shown in Figure 11 at 3 GHz frequency. Comparing the three DRA configurations, the DRA1 and DRA2 have negative 23\({}^{\circ}\) and positive 30\({}^{\circ}\) of beamwidth, while the proposed DRA provide a wide beamwidth of circular polarization with \(\sim\)135\({}^{\circ}\) (\(-\)77\({}^{\circ}\) to 58\({}^{\circ}\)) in phi = 90\({}^{\circ}\) plane. On that account, the proposed CP DRA will have better signal reception as the wide beamwidth assist the antenna to receive signals uniformly over a wider range [28].