## 4 Experimental Verification and Analysis
The CNR variation curves over time for all angles at three operating frequencies are shown in Figure 16:8 Among them, the uniformity of the right-hand circularly polarized signal at the operating frequency \(f=2294.75\) MHz is \(2.379^{\circ}\), the uniformity of the right-hand circularly polarized signal at \(f=2242.8\) MHz is \(2.986^{\circ}\), and the uniformity of the left-hand circularly polarized signal at \(f=2242\) MHz is \(2.997^{\circ}\). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**R94 Frequency Point**} & \multicolumn{2}{c}{**R42 Frequency Point**} & \multicolumn{2}{c}{**L42 Frequency Point**} \\ \cline{2-6}
**Angle (Elevation,** & **Specification** & **Requirements** & **Measured Value** & **Specification** & **Requirements** & **Measureed Value** \\
**(dB/K)** & **(dB/K)** & **(dB/K)** & **(dB/K)** & **(dB/K)** & **(dB/K)** & **(dB/K)** \\ \hline \(10,0\) & & \(-8.69\) & & \(-8.14\) & & \(-7.82\) \\ \hline \(10,90\) & & \(-8.69\) & & \(-8.14\) & &  
From the experimental results in Figure 19, it can be seen that the beamforming algorithm used in this scheme achieves a beam uniformity of less than 3\({}^{\circ}\) at all three operating frequencies. Compared with other beamforming methods, the MVDR method is used for DBF with the array antenna. Due to the sensitivity of the MVDR beamformer to the mismatch between the theoretical and actual direction vectors, the beamforming consistency at the three frequency points mentioned above is greater than 5\({}^{\circ}\). However, by using the beamforming method proposed in this paper, which combines prior information and spatial domain search, the beamforming consistency is improved by more than 2\({}^{\circ}\). (5) Beam Pointing Accuracy Test  
Test Principle: At a specified frequency, a beam is formed to point to the theoretical beam pointing angle \(r_{1}\) within the range of pointing angles. The actual measured beam pointing angle is \(r_{2}\), where \(r_{2}\) is defined as the elevation angle (the angle between the direction and the XoY-plane), as shown in Figure 16:9  
The beam pointing error \(e\) for this instance (i.e., the angle between the two beam pointing vectors \(r_{1}\) and \(r_{2}\)) is  
\[ \begin{split}& e=\arccos\{\left[\sin\theta_{1}\cos\varphi_{1}, \sin\theta_{1}\sin\varphi_{1},\cos\theta_{1}\right]\cdot\\ &\left[\left[\sin\theta_{2}\cos\varphi_{2},\sin\theta_{2}\sin \varphi_{2},\cos\theta_{2}\right]\right]\}^{T}\end{split}  \tag{55}\]  
Figure 19: Beam uniformity test results for the three frequency points. (**a**) Beam uniformity test results for the right-hand circularly polarized signal at the operating frequency f = 2294.75 MHz. (**b**) Beam uniformity test results for the right-hand circularly polarized signal at the operating frequency f = 2242.8 MHz. (**c**) Beam uniformity test results for the left-hand circularly polarized signal at the operating frequency f = 2242 MHz. To assess the beam pointing accuracy, the antenna turntable should be turned to align the vertex of the spherical antenna with the auxiliary transmitting antenna. At this point, the pointing angle in the beam control system is recorded as the theoretical pointing angle. Adjusting the turntable in 0.5-degree steps determines the pointing angle that maximizes the CNR, and the beam pointing error (i.e., beam pointing accuracy) for this test is calculated using Equation (55). The process is repeated five times and the maximum value is taken as the beam pointing accuracy for this angle. The test angle and frequency are changed, and repeated experiments are conducted. The test results are shown in Table 4.  
From the experimental results in Table 4, it can be observed that the beamforming algorithm used in this scheme achieves measured elevation and azimuth angle errors of less than \(2^{\circ}\), with beam pointing errors also less than \(2^{\circ}\). (6) Evaluation of DBF Errors  
The quality of the antenna radiation pattern directly affects the performance of the DBF system.