## 6 Conclusions  
In this paper, an effective method is developed to improve the scanning performances of PAAs. Both modified SIW cavities and SQTs were used. The proposed array-simulated results achieve excellent scanning performance with 2.2 dB gain fluctuation and better than \(-68.1\) dB cross-polarization levels both in the E- and H-plane when scanning up to \(\pm 45^{\circ}\) over the whole working band. Moreover, the proposed PAA achieved symmetric scanning pattern in E-plane. Without any parasitic structure, the array has the advantages of low cost and a simple structure. A 24 \(\times\) 16 array was simulated, fabricated, and measured. The measured scanning radiation patterns demonstrated good agreement with the simulated results. As a result, the presented array is a good candidate for high-performance PAA applications with fixed dimensions. Although it has a wide range of applications and enormous potential, more research and development are required. For example, as proof-of-concept, this study only shifted the blind spot and had a narrow operating bandwidth. Therefore, future research will focus on how to improve the array performance by eliminating blind spots.  
Conceptualization, A.Q. and X.L.; methodology, H.L.; software, T.G.; validation, C.F. and S.Z.; formal analysis, H.L. and X.X.; investigation, T.G.; resources, C.F. and S.Z.; data curation, Z.X.; writing--original draft preparation, H.L. and T.G.; writing--review and editing, H.L.  
\begin{table}
\begin{tabular}{c c c c c} \hline  & \multicolumn{2}{c}{**Simulated**} & \multicolumn{2}{c}{**Measured**} \\ \hline
**Frequency** & **E-Plane** & **H-Plane** & **E-Plane** & **H-Plane** \\ \hline \(f_{l}\) & 1.23 dB @\(\pm 45^{\circ}\) & 2.06 dB @\(\pm 45^{\circ}\) & 2.9 dB @\(\pm 45^{\circ}\) & 2.14 dB @\(\pm 45^{\circ}\) \\ \hline \(f_{0}\) & 1.45 dB @\(\pm 45^{\circ}\) & 1.92 dB @\(\pm 45^{\circ}\) & 2.9 dB @\(\pm 45^{\circ}\) & 2.9 dB @\(\pm 45^{\circ}\) \\ \hline \(f_{h}\) & 1.98 dB @\(\pm 45^{\circ}\) & 1.8 dB @\(\pm 45^{\circ}\) & 3.8 dB @\(\pm 45^{\circ}\) & 3.7 dB @\(\pm 45^{\circ}\) \\ \hline \end{tabular}
\end{table}
Table 2: Simulated/measured scanning loss.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Work**} & **Gain** & **-Pol Level/dB** & **Approaches** & **Pattern** \\  & **Fluctuation** & **(45\({}^{\circ}\)/\(-45^{\circ}\))** & **-** & **SIW cavity** & **Symmetry** \\ \hline
[15] & E: 3 dB @\(\pm 45^{\circ}\) & E: \(-64\) dB @\(45^{\circ}\) & SIW cavity & Asymmetry \\ \hline
[16] & E: 0.5 dB @\(\pm 15^{\circ}\) & E: \(-64\) dB @\(45^{\circ}\) & SIW cavity & Asymmetry \\ \hline
[21] & E: 4.1 dB @\(\pm 60^{\circ}\) & E: \(-29\) dB @\(60^{\circ}\) & SQT & Symmetry \\ H: 5.2 dB @\(\pm 60^{\circ}\) & H: \(-23\) dB @\(60^{\circ}\) & & \\ \hline This work & E: 2.9 dB @\(\pm 45^{\circ}\) & E: \(-72.3\) dB @\(45^{\circ}\) & & \\ \hline \end{tabular}
\end{table}
Table 3: A comparison with the state-of-the-art proposed PAA.  
and A.Q.; supervision, A.Q., and X.L.; project administration, X.L.; funding acquisition, H.L., X.X., and X.L. All authors have read and agreed to the published version of the manuscript.  
This work was supported in part by the Key Research and Development Program of Zhejiang Province under Grant No. 2022C01093, in part by National Natural Science Foundation of China under Grant No. 62271122, in part by Huzhou Municipal Natural Science Foundation of China under Grant Nos. 2023 YZ19, and in part by Scientific Research Foundation for Yangtze Delta Region Institute of University of Electronic Science and Technology of China, Huzhou, under Grant No. U03220083.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors declare no conflicts of interest.