## 3 Results and Analysis  
### Simulation Results  
The simulated reflection coefficients for normal incidence, showing both the frequency dependence and the variation with polarization angle (\(\varphi\)) from \(0^{\circ}\) to \(180^{\circ}\), are shown in Figure 2.  
It is clear from Figure 2 that the metasurface of the unit cell in Figure 1 (for both models) exhibits a polarization-dependent characteristic when the polarization is varied from \(0^{\circ}\) to \(180^{\circ}\), especially around 5 GHz where the reflection becomes small (absorption becomes large). As shown in Figure 2, the minimum reflection coefficient occurs at 5.122 GHz (absorption \(>98\%\)) at \(\varphi=0^{\circ}\) and 5.144 GHz (absorption \(>99\%\)) at \(\varphi=10^{\circ}\), respectively, based on the two models. These shifts in resonant frequency are mainly caused by changes in the resistor position and structure. The frequency variations in S11 as shown in Figure 2 are mainly due to the resonant behavior of the unit cell, where the interaction between the incident electric field and the lumped resistor varies with polarization angle. Changes in polarization affect the current distribution and impedance matching, leading to variations in the reflection coefficient across frequencies. The voltage across the lumped resistor is obtained directly from the CST simulation results. This voltage represents the peak (not root mean square, or RMS) amplitude across the resistor. Based on the simulated voltage, the total power harvested across the load R can be calculated using Equation (1), which is as follows:  
\[P_{load}=\frac{V^{2}}{2R} \tag{1}\]  
Figure 2: Reflection coefficients for the unit cell in Figure 1 for normal incidence with different polarization angles. (**a**) Model A and (**b**) Model B.  
where \(V\) is the voltage amplitude (not the RMS value) of the lumped resistor and \(P_{l}\) is the total energy harvested on the lumped resistor \(R\). The lumped resistor was inserted in the unit cell. Choosing the right lumped resistor value can increase the absorption value through impedance matching with free space. The energy absorbed by our structure cannot be completely absorbed by the lumped resistor since some of it is dissipated by dielectric loss in the substrate. In this model, the energy dissipated by dielectric loss is 2.3%. This dielectric loss is frequency-dependent, primarily characterized by the loss tangent (tan \(\delta\)) which arises from polarization relaxation under time-varying electric fields. Effective metasurface design can minimize energy dissipation during electromagnetic interactions [31]. Figure 3 shows the voltage in each model for normal incidence. Maximum voltage occurs at polarization angles equal to \(\varphi_{p}=0^{\circ}\) and \(10^{\circ}\) for Models A and B, respectively. The polarization angle where the energy absorbed by the lumped resistor is minimum is shown in Figure 3 by the appearance of a minimum voltage that does not depend on frequency. We call this condition the dip phenomenon, which is clearly visible when the voltage across the lumped resistor changes with changing polarization angle, which is a polarization-dependent characteristic. For all models a voltage dip was always found at a specific angle. In the first model, the dip appears at a polarization angle of \(90^{\circ}\). In the second model, the dip appears at a polarization angle of \(100^{\circ}\). For a geometrical structure the dip phenomenon occurs when the position of the lumped resistor from the center of the patch has an angle of \(90^{\circ}\) to the direction of the electric field, as shown in Figure 3. It can be analyzed that when the electric field is perpendicular to the line connecting the lumped resistor position and the patch center no effective voltage is developed along that direction on the patch. As a result, no voltage difference is established between the patch and the ground and the lumped resistor does not absorb any current.