## 5 Conclusions  
This paper presents a systematic investigation into the polarization characteristics of a symmetrical, square patch metasurface unit cell designed for RF energy harvesting, using a single via and a single lumped resistor. Both simulation and experimental results exhibit polarization-dependent characteristics and confirm the existence of a voltage dip at specific polarization angles, which occurs when the direction of the electric field is perpendicular to the position of the resistor relative to the center of the patch. This behavior reveals a fundamental sensitivity to polarization in such structures.  
The key novel contribution of this work is the establishment and experimental validation of a linear relationship between the geometric position angle of the resistor and the resulting polarization dip angle. This relationship is consistently demonstrated across both simulation and measurement and is independent of frequency. Unlike previous studies that only reported polarization characteristics at a limited number of polarization angles, this paper presents a predictive design rule that enables engineers to determine the dip angle directly from the resistor's geometric placement. This insight sets the present work apart and provides a quantitative foundation for future metasurface design strategies involving polarization-dependent behavior.  
Additionally, this study explored, through both simulation and measurement, an asymmetric patch design as a potential approach to mitigate sharp voltage dips and improve stability under varying polarization conditions. While asymmetry reduces dip sharpness it also leads to a decrease in absorption efficiency under linearly polarized waves. Therefore, designers must balance robustness to polarization variations with maximum energy harvesting performance depending on the intended application. In conclusion, the findings of this study provide a new framework for designing metasurface energy harvesters based on predictable and tunable polarization behavior. Further analysis of polarization-dependent behavior based on detailed analysis through equivalent circuit models or field distribution theory will enhance the applicability of this work. Future research may also include further exploration of both various symmetric and asymmetric geometries, investigation over wider frequency bands, and consideration of fabrication-related effects that may influence dip characteristics and measurement accuracy.  
Conceptualization, E.M.P. and S.Y.; methodology, E.M.P.; validation, E.M.P. and S.Y.; formal analysis, E.M.P.; investigation, E.M.P. and S.Y.; resources, S.Y.; writing--original draft preparation, E.M.P.; writing--review and editing, S.Y., T.I. and M.O.; supervision, S.Y. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding authors.  
The first author would like to express gratitude to the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) Japan and the Japan International Cooperation Agency (JICA) for providing the scholarship during the study at Kanazawa University, Japan.  
The authors declare no conflicts of interest.