## 5 Finite Array Experimental Results  
To meet the requirements for radar system, a 24 \(\times\) 16 (384-element) PAA of Array 3 was simulated, fabricated, and measured, as depicted in Figure 11a. Due to confidentiality requirements, the center operating frequency is replaced by \(f_{\rm o}\). As the fabricated array is a 24 \(\times\) 16 (384-element) array, the overall size of the array is 12.72 \(\lambda_{0}\)\(\times\) 8.48 \(\lambda_{0}\). The proposed array structure is a double-layer microwave board, which is manufactured on the basis of conventional PCB technology. The microwave board is welded onto the support metal plate via the tin-lead solder process after the subminiature version P (SMP) connectors \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Work**} & **Peak** & **Scan Loss/dB** & **Blind Spot** & \begin{tabular}{c} **X-Pol Level/dB** \\ **(45\({}^{\circ}\)/\(-\)45\({}^{\circ}\))** \\ \end{tabular} & **Pattern** \\ \hline Array 1 & 23.7 & \begin{tabular}{c} E: 2.3/3.8 \\ H: 3.3/3.3 \\ \end{tabular} & \(\oplus\)1.06\(f_{\rm 0}\) & \begin{tabular}{c} E: \(-66.2\) \\ H: \(-5.32\) \\ \end{tabular} & Asymmetry \\ \hline Array 2 & 23.7 & \begin{tabular}{c} E: 2.1/2.6 \\ H: 2.3/2.8 \\ \end{tabular} & \(\oplus\)1.09\(f_{\rm 0}\) & \begin{tabular}{c} E: \(-73.1\) \\ H: \(-8.97\) \\ \end{tabular} & Asymmetry \\ \hline Array 3 & 23.6 & \
\begin{tabular}{c} E: 2.3/2.3 \\ H: 2.1/2.1 \\ \end{tabular} & \(\oplus\)1.09\(f_{\rm 0}\) &
\begin{tabular}{c} E: \(-75.5\) \\ H: \(-74.5\) \\ \end{tabular} & Symmetry \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the three PAAs. Figure 10: Normalized patterns of Array 3 at \(f_{h}\): (a) E-plane, (b) H-plane, and (c) D-plane. have been soldered on it. Most notably, the SMP connector is the optimization choice for antenna at the Ku band. Uniform amplitude distribution is used in the PAA aperture. The 384-element PAA is tested using an active T/R module. The calibration of the 384-element PPA was initially conducted successfully using the method in [30] with a near-field antenna probe across the operating frequency range. However, only phase calibration was carried out for the phased array. Figure 11b shows the PAA during performance characterization measurements in the anechoic chamber. Since the active PAA only tests EIRP, the gain is not measured separately. Figure 12 plots the simulated realized peak gains and efficiency of proposed 384-unit PAA. The theoretical aperture gain is calculated using 4\(\pi\mathcal{S}/{\lambda_{0}}^{2}\), where S is the aperture area of PAA, and \(\lambda_{0}\) is the wavelength of operating frequency in free space. The simulated gain is higher than 31 dBi at broadside and higher than 28.4 dBi when steering up to \(\pm 45^{\circ}\). The simulated efficiency is higher than 85% at broadside in the operating bandwidth. We can see that the array gain gradually increases with frequency and decreases with scanning angle. Figures 13-15 present the measured and simulated scanning performances at \(f_{l},f_{0}\), and \(f_{h}\) in E- and H-planes. The scanning angles of the presented array are \(0^{\circ}\), \(\pm 30^{\circ}\), and \(\pm 45^{\circ}\) in the two orthogonal principal planes. The cross-pol levels in E- and H-planes were too low to be measured, and only simulated cross-polarization was provided. It can be seen that the proposed 24 \(\times\) 16 array showed the ability to scan up to \(\pm 45^{\circ}\) in E- and H-planes without grating lobes. Figure 11: Fabricated prototype: (**a**) photograph of the fabricated 24 \(\times\) 16 prototype; (**b**) pattern measurement setup. Figure 12: Simulated current distributions of the center element. Figure 14: Normalized patterns at \(f_{0}\): (a) E-plane and (b) H-plane. Figure 13: Normalized patterns at \(f_{1}\): (a) E-plane and (b) H-plane. At \(f_{l}\), the proposed PAA exhibits gain fluctuations of 1.2 dB and 2.1 dB in E- and H-planes, respectively, with a scanning coverage of 45\({}^{\circ}\).