# A Compact Sequentially Rotated Circularly Polarized Dielectric Resonator Antenna Array
## 4 Measurement Results and Discussions
### SR 2 \(\times\) 2 Array Results  
Figure 10 shows the assembled geometry of the proposed CP DRA array. The proposed antenna uses Duroid RO4003C as a substrate with a dielectric constant of 3.38 from Rodgers. The substrate size was 54 \(\times\) 50 \(\times\) 0.813 mm\({}^{3}\). The DRs were made of E-11 material from T-cream with a dielectric constant of 11.5. The dimensions of the resonating elements were fine-tuned to achieve optimum performance. The DR dimensions were 9, 9, and 6 mm in length, width, and height, respectively. The elliptical slots were printed at the bottom of  
Figure 8: Reflection coefficient variation with respect to ES radii: (**a**) Radius \(a\); (**b**) Radius \(b\); (**c**) RDR dimensions variations.  
the substrate with radius \(a\) equal to 5.5 mm and radius \(b\) equal to 2.5 mm. On the other side of the substrate, copper was etched to form a microstrip feed network.  
Figure 11 shows the simulated and measured return losses. The minimal measured resonance was achieved at 5.87 of \(-\)15.72 dB, whereas the bandwidth ranged from 5.1 to 6.05 GHz. Meanwhile, the simulated resonance achieved a value of \(-\)15.28 dB at 5.85 GHz and a bandwidth that ranged from 5.078 to 6.08 GHz. The agreement between the simulated and measured return losses was acceptable, which was attributed to the accuracy of the simulation enivenment settings and measurement conditions.  
Figure 12 illustrates the simulated and measured electric fields at the electric co-polarized and electric cross-polarized planes at a frequency of 5.8 GHz. From the figure, we can infer that the polarization is a left-hand circular polarization (LHCP) in the broad side direction. The difference between the cross-polarization and co-polarization at the xz-plane was approximately \(-\)20 dB.  
Figure 13 shows the simulated and measured gains over the resonance ranges. The maximum simulated gain occurs at 5.35 GHz of 10.32 dBi, while that of the measured gain occurs at 5.34 GHz of 10.24 dBi. The measured gain was extracted using a gain transfer  
Figure 10: Photograph of the fabricated single element DRA: (**a**) The feeding network printed on the front plan; (**b**) The elliptical slots etched on the ground plan; (**c**) The dielectric resonators placed on the elliptical slots.  
Figure 9: The AR variation corresponding to elliptical slot radii alteration: (**a**) Radius \(a\); (**b**) Radius \(b\).  
method using a helical antenna as a reference. A reflector at the feeding network side might be used to increase the gain performance. The simulated total efficiency ranges from 0.7% to 0.9, confirming the effectiveness of the design.  
Figure 14 shows the simulated and measured ARs at the main angle of 0\({}^{\circ}\). The simulated AR bandwidth ranges from 5.08 to 6.08 GHz, while the measured AR ranges from 5.05 to 6.05 GHz. The simulated and measured AR impedance bandwidth was 17.9% and 18% respectively. The agreement between the simulated and measured results was fairly good.  
Figure 11: Simulated and measured return losses.  
Figure 12: Simulated and measured electric co-polarized and electric cross-polarized fields.