## 3 Unit Cell Design  
Figure 2 presents the structure of a multi-layer unit cell. Roger RT 6006 is used as a substrate. The strategic deployment of the middle and top layers is aimed at achieving the utmost efficiency in both transmission and reflection. The outcomes substantiate that the metasurface allows for the conversion of the transmission frequency range into a fully encompassing reflection frequency range, and vice versa. Table 1 lists the dimensions associated with a single unit cell.  
Figure 1: Conceptual illustration for the proposed TRA metasurface (**a**) TM waves and (**b**) TE waves.  
Figure 2: Structure of a unit cell with three metal layers and its perspective view.  
Figure 3 displays the S-parameter characteristics of a unit cell for both the TM and TE modes. The analysis reveals that in the TM mode, the unit cell functions as a transmission mode element at lower frequencies, specifically around 6.3 GHz, whereas it operates as a reflective mode element at higher frequencies, such as 9.3 GHz. Conversely, in the TE mode, the unit cell behaves as a reflective element at a lower frequency, approximately 6.3 GHz, and shifts to a transmission band role at a higher frequency, around 9.3 GHz.  
Figure 4 depicts the phase responses for reflection and transmission in both the TM and TE modes. These phase responses are observed for both lower- and higher-frequency bands.  
The reflection phase of the proposed TRA metasurface can be controlled by varying the width (Wp) of the patch.  
The influence of the \"Wp\" variation in the reflection phase response is demonstrated in Figure 5. Examination of Figure 5 reveals that within the realm of the transverse electric (TE) mode, altering \"Wp\" across 2 to 5 mm elicits a fluctuation in the reflection phase from 100\({}^{\circ}\) to -100\({}^{\circ}\). Conversely, for the transverse magnetic (TM) mode, the reflection  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Parameter** & **Size (mm)** & **Parameter** & **Size (mm)** & **Parameter** & **Size (mm)** \\ \hline J\({}_{W}\) & 7.5 & Wp & 4.2 & J4 & 0.4 \\ J1 & 7.5 & Lp & 3.8 & J5 & 0.5 \\ Tw \& TI & 3.2 & J1 & 0.6 & J6 & 1.6 \\ T\({}_{W}\) & 3.8 & J2 & 6 & J7 & 0.3 \\ h & 0.8 & J3 & 1.4 & J8 & 0.3 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Attributes of the proposed unit cell.  
Figure 4: Reflection and transmission phase of the unit cell: (**a**) TM mode and (**b**) TE mode.  
Figure 3: S-parameters: (**a**) TM mode and (**b**) TE mode.  
phase experiences a transformation spanning from 160\({}^{\circ}\) to \(-\)140\({}^{\circ}\), as illustrated in the same figure. This intricate relationship between \"Wp\" adjustments and the resultant shift in the reflection phase underscores the dynamic control and adaptability achievable in the proposed system, affording tailored electromagnetic responses in tune with specific operational requirements. Likewise, the impact of \"Wp\" on transmission phase characteristics is elucidated in Figure 6. The discernible trend showcases that, through the manipulation of \"Wp\" within the interval of 3 to 4.5 mm, a consistent transmission phase of approximately 100\({}^{\circ}\) manifests itself in both TE and TM modes. This result underscores the controllable and robust nature of the proposed system, wherein adjustments to \"Wp\" engender uniform transmission phase behaviors across different polarization states, ensuring coherent and desirable electromagnetic propagation outcomes.