# Exploring Carbon-Fiber UAV Structures as Communication Antennas for Adaptive Relay Applications
## 3 Results
### Propagation Models Results
Another important result obtained from the experimental campaign is the plotting of the Influence of the Polarization curve, presented in Figure 18.  
Figure 17: Influence of distance between the two antennas. Figure 18: Influence of polarization. As anticipated, even a slight misalignment in polarization leads to a significant drop in received power. Specifically, a 90\({}^{\circ}\) change in polarization results in a considerable 15 dBm decrease in received power. Hence, it can be seen that antennas have to be aligned properly and polarized for optimal performance. Figure 19 illustrates the elevation radiation pattern of Antennas A and B, measured after rotating Antenna A by 90\({}^{\circ}\) relative to Antenna B. This setup was designed to assess the influence of the relative angle between antennas on received signal strength. From the polar plot, a general decrease in received power is evident across most angles, confirming the expected behavior when antenna orientation is not aligned. Both radiation patterns exhibit a distinct directional profile, with signal strength primarily concentrated between 20\({}^{\circ}\) and 70\({}^{\circ}\), and noticeable reductions beyond these angles. Antenna B (red curve) shows slightly stronger and broader radiation in certain elevation sectors compared to Antenna A (blue curve), which appears more concentrated and narrower in its main lobe. The dip in signal amplitude, especially between 100\({}^{\circ}\) and 160\({}^{\circ}\), reflects the impact of polarization mismatch and misalignment, as the antennas are no longer optimally oriented for maximal power transfer. Reinforcing the fact that antenna alignment and polarization are critical factors for achieving optimal performance. In the second half of the graph, the two antennas exhibit a radiation pattern that closely mirrors the first half, demonstrating the expected symmetry in their polar response. This symmetry suggests that the antenna structures and their surrounding environments do not introduce significant distortion or asymmetry in the radiation behavior. While minor variations in amplitude can still be observed--particularly in the sidelobes--these differences are within acceptable limits and do not significantly affect the overall performance. Overall, Figure 19 demonstrates that even modest angular deviations between antennas can significantly affect the radiation pattern and received power, emphasizing the importance of precise orientation in UAV communication systems [23]. Following the experiment conducted using the two-ray model, this configuration allowed the formation of both a direct wave and a ground-reflected wave. Under these conditions, the received power dropped significantly to \(-57.42\) dBm. After the gaps were refilled with absorbers, the received power increased to \(-55.73\) dBm. Following the experiment, Figure 20 presents the Influence of the Position of a Hole, while Figure 21 illustrates the Influence of the Number of Holes. Figure 19: Radiation pattern in Elevation difference. Figure 20 shows the influence of the position of a single hole in the absorber arrangement on the received power level. The horizontal axis indicates the position (from \"No hole\" to \"Row 9\"), while the vertical axis represents the received power in dBm. It can be observed that the presence of a hole consistently decreases the received power compared to the case with no hole at all. However, the exact position of the hole matters, with Row 1 and Row 4 producing the lowest power values (around -57.5 to -58 dBm), suggesting stronger destructive interference due to multipath effects at those positions. In contrast, holes in Row 2, Row 5, and Row 7 resulted in higher received power, closer to \(-55\) dBm, implying more constructive interference or a lesser impact of reflection phase shift at those locations. The relative difference between the highest and lowest received power values is 5.13%, highlighting the measurable impact that even small changes in absorber configuration can have on signal strength.