## 3 Analysis of the Received Jamming Power in the UAV Jamming Link Due to the Attitude Change  
Figure 3 shows the configuration of a small hovering UAV jammed by a jammer on the ground. The positions of the UAV and jammers are defined in the global coordinate system. The UAV is at height \(h\) from the origin of the global coordinate system and the jammer is at \((x,\ y,\ z)\) on the ground. In Figure 3, \(\overline{\mathbf{R}}_{A}\) is the vector from the UAV position to the jammer position and \(EL\) is the elevation angle, which is the included angle between the vector \(\overline{\mathbf{R}}_{A}\) and the horizontal plane at the jammer position. If both the jammer antenna and the UAV antenna use an omnidirectional vertically polarized antenna, there is no polarization loss in the UAV jamming link, regardless of the height of the UAV and the position of the jammer. However, if the UAV attitude changes, polarization loss may occur. As an example of UAV attitude change, we considered UAV roll rotation. The UAV roll rotation has a roll axis \(\hat{\mathbf{n}}_{R}\) of \(\hat{x}\) and a roll angle \(\theta_{R}\) of \(20^{\circ}\). When the UAV has a constant height and the jammer is on a plane ground, the variation in the received jamming power due to the UAV roll according to the \((x,\ y)\) position of the jammer is shown as a contour and shadow map in Figure 4. The area where the UAV antenna gain in the initial attitude is less than 10 dB compared to the maximum gain is indicated by a dotted line and is called a blind zone. Figure 2: The elevation and azimuth location \(\theta_{A}\) and \(\phi_{A}\) for the jammer antenna on the ground in reference to the local coordinate system of the UAV antenna \((\hat{\mathbf{n}}_{A},\ \hat{\mathbf{\rho}}_{A},\ \hat{\mathbf{w}}_{A})\). Figure 4: Contour and shadow map of the variation in received jamming power due to the UAV roll (\(\hat{n}_{R}=\hat{x}\), \(\theta_{R}=20^{\circ}\)); where the UAV height \(h\) is at **(a)** 0 m, **(b)** 250 m, **(c)** 500 m, and **(d)** 1000 m, and the jammer is on plane ground. Figure 3: Configuration of the small hovering UAV jammed by a jammer on the ground considering the UAV roll (UAV height: \(h\), the roll axis: \(\hat{n}_{R}\), the roll angle: \(\theta_{R}\)). Figure 4a shows the case when the height of the UAV and the jammer are the same. The line with \(x=0\) m is perpendicular to the axis of rotation. Thus, there is no PLF variation. On the other hand, on the line with \(y=0\) m, there is no gain variation. Thus, the power variation shown in \(-0.76\) dB and \(-0.54\) dB in \(x=0\) m and \(y=0\) m are due only to gain and PLF variations, respectively. In other locations, the power variations are contributed both from the gain and PLF variations. Figure 4b-d shows the cases when the height of the UAV and the jammer are different. As in Figure 4a, the power variations in \(x=0\) m are due only to gain variation. In other locations, the power variations are contributed both from the gain and PLF variations. The variation is overall increased as the height difference increases because the jammer location is closer to the null direction of the omnidirectional antenna, where the gain and polarization variation is large. In order to show the contributions of the gain and PLF variations separately, they are separately shown in Figures 5 and 6. It can be seen that Figures 4 and 5 are almost the same because the gain variation is dominant in most locations. However, near the rotation axis, the two sets of figures are notably different because of the contributions from the PLF variation. The contribution from the PLF variation is shown in Figure 6. As shown in Figure 6a, when the height of the UAV and the jammer are the same, the maximum variation in the PLF of \(-0.54\) dB \(\left(=10\log\left(\cos(20^{\circ})^{2}\right)\right)\) occurs in \(y=0\) m, which is the axis of rotation.