# A Circularly Polarized Non-Resonant Slotted Waveguide Antenna Array for Wide-Angle Scanning
## 4 Verification and Comparison
### Simulation and Measurement Results  
The prototype antenna was verified, and the simulation and measurement results are presented below. The VSWR and S21 of the eight- and nine- element linear arrays were measured, respectively, abd the results are shown in Figure 17. It is observed that the measured results closely align with the simulation, indicating good agreement.  
Figure 18 presents the radiation patterns of the proposed antenna. Figure 18a-c depict the elevation radiation patterns at 6.6 GHz, 6.8 GHz, and 7.0 GHz, respectively. The majority of the simulation and measurement results exhibit close agreement. However, there are slight discrepancies in the right side-lobe level (SLL) at 6.8 GHz, although all measured SLL results remained below \(-20\) dB. Furthermore, the frequency scan angle results align well with those of the simulation. The azimuth radiation pattern results are depicted in Figure 16d-f; all measured azimuth radiation results exhibit good concordance with the simulation data. Additionally, the achieved side-lobe levels (SLLs), at approximately \(-14\) dB, are attributed to the utilization of an equal-amplitude power divider.  
Figure 16: (**a**) The fabricated antenna. (**b**) The power divider. (**c**) The experimental setup for measurements.  
this problem, the circular polarizer layer and the waveguide layer should be connected using both screws and conductive adhesive, and the position of the screws needs to be redesigned to address the deformation problem after assembly. Enhancing the fabrication accuracy and applying an adhesive to the metal layers can mitigate the frequency offset.  
The advantage of the proposed antenna is the wide beam scan angle; the phase scan radiation pattern in 6.8 GHz is plotted in Figure 20. The results show that the antenna can realize beam scanning in the range of \(-45^{\circ}\)\(\sim\)+\(45^{\circ}\) without a grating lobe; the phase mismatching effect is entirely suppressed. Table 4 shows the axial ratio result in the phased scan condition; the scanned beam can still maintain a 3 dB axial ratio under the machine error.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Scan Angle** & \(-\)**45\({}^{\circ}\)** & **0\({}^{\circ}\)** & **+45\({}^{\circ}\)** \\ \hline Axial Ratio (Sim.) & 3.33 dB & 0.23 dB & 2.69 dB \\ Axial Ratio (Mea.) & 2.3 dB & 2.9 dB & 2.2 dB \\ \hline \hline \end{tabular}
\end{table}
Table 4: A comparison of the measured (Mea.) and simulated (Sim.) axial ratio results for a 6.8 GHz phase scan.  
Figure 19: The measured and simulated axial ratios at 11\({}^{\circ}\), 12\({}^{\circ}\), and 13\({}^{\circ}\) at 6.6–7.2 GHz.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Frequency/GHz** & **AR at 11\({}^{\circ}\)/dB** & **AR at 12\({}^{\circ}\)/dB** & **AR at 13\({}^{\circ}\)/dB** \\ \hline
6.7 & 2.01 & 2.01 & 2.00 \\
6.8 & 0.24 & 0.10 & 0.12 \\
6.9 & 1.44 & 1.43 & 1.41 \\
7.0 & 3.76 & 3.71 & 3.64 \\ \hline \hline \end{tabular}
\end{table}
Table 3: The simulated axial ratio (AR) results in the azimuth plane.  
Figure 20: The measured and simulated phased scan radiation patterns in the azimuth plane: **(a)** in the normal beam direction; **(b)** in the +45\({}^{\circ}\) beam direction; **(c)** in the \(-45^{\circ}\) beam direction.