## 2 Antenna Design and Optimization
### Parametric Analysis
#### 2.2.2 Axial Ratio  
To achieve effective circular polarization in the proposed antenna design, three critical parameters were identified: the length of the truncated corners (L1), the width of the added rectangular stubs (Ws), and the diameter of the arc added to the lower edge of the circular slot on the top side (arc_r). Extensive simulation studies revealed that the practical length of the truncated corners (L1) should be 9 mm, which represents an improvement over the 7 mm utilized in Antenna 1 and 8.25 mm in Antenna 2. Correspondingly, the width of the added rectangular stubs (Ws) was optimized to 4.75 mm, compared to 5.75 mm in Antenna 1 and 4.5 mm in Antenna 2. For the diameter of the added (arc_r), the optimal centered position was determined to be at 10.75 on the \(x\)-axis and 13.475 on the \(y\)-axis, originating from the left corner of the design, with a diameter of 3 mm as an adjustment from the 4 mm used in Antenna 1 and 2.55 mm in Antenna 2. These refinements collectively enhance the antenna's performance in achieving effective CP and broadening its operational capabilities. Changing the Parameter Element L1  
As shown in Figure 8, the design was simulated for different parametric values of (L1), which represents the length of the truncated corners. It was observed that the AR varies considerably with changes in this parameter. Specifically, when (L1) is set to 9 mm, the AR demonstrates optimal tuning across the entire established frequency range, indicating effective CP. Further simulations revealed that reducing (L1) to values below 9 mm resulted in a significant increase in the AR, exceeding the desired threshold of 3 dB, which compromised the antenna's polarization performance. Conversely, increasing (L1) beyond 9 mm led to a narrower operating bandwidth and a less stable AR, which negatively impacted the antenna's overall efficiency. These findings underscore the importance of fine-tuning the truncated corner lengths in the design process, as they not only influence the  
Figure 7: Return loss of the parameter WH_cut. AR but also have a cascading effect on the overall antenna performance. By systematically optimizing (L1) along with other parameters, the design achieves a robust configuration that effectively supports dual-band operation while maintaining the integrity of CP. Changing the Parameter Element Ws  
As shown in Figure 9, the design was simulated for different parametric values of (Ws), which represents the width of the two added stubs. It was observed that the AR varies considerably with changes in this parameter. Specifically, when (Ws) is set to 4.75 mm, the AR achieves optimal tuning across the entire established frequency range, indicating an effective CP performance. Further analysis revealed that decreasing (Ws) to values below 4.75 mm resulted in an undesirable increase in the AR, exceeding the target of 3 dB, which adversely affected the antenna's ability to maintain consistent polarization. Conversely, increasing the width of the stubs beyond 4.75 mm led to a reduction in ARBW, highlighting the importance of precise tuning. These results emphasize the critical role of stub width in the overall antenna design process. By systematically varying (Ws) alongside other key parameters, the antenna can maintain a robust performance across dual-band operations while effectively supporting the requirements for CP. This fine-tuning approach ultimately enhances the antenna's suitability for reliable communication in UAV applications. Changing the Parameter Element arc_r  
As shown in Figure 10, the design was simulated for different parametric values of (arc_r), which represents the diameter of the two added circular arcs. It was observed that  
Figure 8: Axial ratio versus frequency for different values of the parameter L1. Figure 9: Axial ratio versus frequency for different values of the parameter Ws. the AR varies considerably with changes in this parameter.