## 3 Metasurface Simulation Results  
The MS reflector structure, including the DC bias circuit, is shown in Figure 5. The MS structure and the simplicity of DC biasing reduces the complexity and the absorption of the unit cell (Figures 3 and 4). The via and the clearance add losses to the unit cell due to the need to provide a DC bias to each varactor. The stripes of the unit cells are used as a DC ground for the varactors in one stripe column, eliminating the need for an additional via in each unit cell. The shorter strip is used for supplying the DC bias through a via, enabling each MS unit cell to be independently biased. Figure 5 describes the MS structure including the DC bias circuit where \(\Delta\phi_{x}\) and \(\Delta\phi_{y}\) are the reflected phase differences between two adjacent unit cells in X and Y, respectively. The array size was 40.8 mm \(\times\) 40.8 mm with 12 rows and 16 columns of unit cells, yielding 192 independent unit cells with a separate DC voltage connection, as required. Beam steering in one dimension (the X axis, in this case) requires that every unit cell in each column is connected to the same DC voltage/basis to get the desired \(\Delta\phi_{x}\) while \(\Delta\phi_{y}\)= 0\({}^{\circ}\). The steering angle \(\theta\) for each angle was calculated, as shown in Table 3 using (1). \[\theta=\sin-1\ (\lambda\cdot\Delta\phi_{x}/360\cdot\Delta X) \tag{1}\]  
where \(\Delta X\) is the distance between the center of two adjacent unit cells, and \(\lambda\) is the operating frequency wavelength. The MS was simulated using CST code for a normal incident TEM plane wave of approximately 28 GHz. The simulation results are shown in Figure 5. Results show the main lobe difference to the side lobe at more than 10 dB. The results can be improved by approximately 3 dB by using the optimal phase dynamic range with the stripes configuration. For the beam-steering mode, considering the dynamic phase range and MS size, the phase difference parameter \(\Delta\phi_{x}\) is limited according to Equation (2) for type A and Equation (3) for type B.  
\[236^{\circ}\geq 11\times\Delta\phi_{x} \tag{2}\]  
\[140^{\circ}\geq 7\times\Delta\phi_{x} \tag{3}\]  
In Figure 6a, beam steering at \(\theta\) = 0\({}^{\circ}\) around the resonant frequency with the highest absorption is shown. The solid red line describes the beam reflected gain of one stripe (uniform) MS and the solid green line describes the beam reflected gain for the three stripe configuration. The three-stripe gain curve showed significantly better performance compared to the gain in the one-stripe configuration (red line) by approximately 3.6 dB. Fur  
Figure 5: MS structure with varactor DC biasing method. (**a**) MS top layer. (**b**) MS back layer with varactors’ DC bias indexes. (**c**) 3D inside view of the MS with the closure of the electrical circuit for each varactor [8]. The co-polarization and cross polarization properties of the proposed three-stripe MS was investigated for the case of 9\({}^{\circ}\) beam steering. The simulation results show that most of the transmitted power was reflected in the co-polarization. The cross polarization was below 50 dB, referring to the co-polarization, as seen in Figure 8.  
There was a correlation between the calculation in Equation (1) for beam steering and the simulation results. The stripes configuration improved the performance of the reflected beam gain by 3 dB. A significant improvement in the reflected beam angle \(\theta\) for different frequencies around the operating frequency (bandwidth) was obtained with the three-stripe configuration, compared to the typical uniform configuration (one stripe). Figures 9 and 10 show the influence of a slight change in the operating frequency of the MS. The accuracy in the beam steering angle for the three-stripe configuration was about 50% better than for the typical one-stripe configuration.