# A Compact Planar Wi-Fi Antenna with Optimized Radiation Patterns for Small UAV Applications
## 4 The Comparisons of Simulated Data and Measured Results of The Prototype
### Radiation Patterns  
Figures 14-16 show the comparisons of the simulated and measured radiation patterns of the proposed antenna in the x-y, x-z, and y-z planes. The simulated data show that the proposed antenna has good vertically polarized radiation. Figure 14a,b show the radiation patterns of the proposed antenna in the x-y plane at 2.4 and 5.8 GHz, respectively, and the vertically polarized radiations are quasi-omnidirectional. Due to the hand-soldered tins on the main radiation areas of 2.4 GHz, the measured horizontally polarized radiation is larger than the simulated one, as shown in Figure 14a.  
In the x-z and y-z planes, due to the cable effect, the measured horizontally polarized radiations are much larger than the simulated data, as shown in Figures 15 and 16. In addition, due to the cable effect, the measured vertically polarized radiation is larger than the simulated one at \(-120^{\circ}\) to \(+120^{\circ}\) in the y-z plane at 5.8 GHz, as shown in Figure 16b.  
Figure 14: Comparison of the proposed antenna’s simulated and measured radiation patterns in the x–y plane. (**a**) 2.4 GHz; (**b**) 5.8 GHz.  
Figure 13: The comparison of the simulated and measured reflection coefficients of the proposed antenna.  
The simulated vertically polarized radiation patterns at 2.4 GHz are quasi-omnidirectional, and the maximum radiations in the x-z and y-z planes are near the horizontal plane, as shown in Figures14a, 15a and 16a. The simulated vertically polarized radiation patterns at 5.8 GHz have stronger radiation in the upper hemisphere (below the UAV), as shown in Figures 15b and 16b. Its maximum radiations in the x-z and y-z planes are in the upper hemisphere and between 14 and 29\({}^{\circ}\) from the horizontal plane.  
Table 2 displays the characteristics of the simulated vertically polarized radiation patterns. Ignoring the influence caused by the hand-soldered tin and the measurement system's cable effect, all measured radiation pattern results agree with simulated data. In E-planes, the beamwidths of relative \(-10\) dB at 2.4 GHz are no less than 142\({}^{\circ}\). Moreover, at 5.8 GHz, maximum gain angles are between 17 and 29\({}^{\circ}\) off the horizontal.  
Table 3 compares the proposed antenna and published works on planar antennas. The proposed planar antenna has the following advantages. First, it has a single-sided structure, which has a relatively low cost to make small UAVs more affordable. Second, it has a minimum electrical length (L) of 0.132 \(\lambda_{0}\) and a low profile (h) of 0.0128 \(\lambda_{0}\) to meet the portability and aerodynamic requirements for small UAV applications. Third, at 5.8 GHz, it has stronger radiation in the upper hemisphere (below the small UAV) to reduce interference from rare-use directions. Its maximum radiations are below the UAV and between 14 and 29\({}^{\circ}\) from the horizontal plane to provide more antenna gain when the small UAV flies farther in urban areas. At 2.4 GHz, it has quasi-omnidirectional radiation to ensure a stable link in all directions. Its maximum radiations are near the horizontal  
Figure 16: Comparison of the proposed antenna’s simulated and measured radiation patterns in the y–z plane. (**a**) 2.4 GHz; (**b**) 5.8 GHz.  
Figure 15: Comparison of the proposed antenna’s simulated and measured radiation patterns in the x–z plane. (**a**) 2.4 GHz; (**b**) 5.8 GHz.  
plane to provide more antenna gain when the small UAV flies farther in open areas. Finally, it has good vertically polarized radiation at 2.4 and 5.8 GHz for long-distance applications.