## 4 Unit Cell Simulations and Experimental Results  
The proposed unit cell properties and the MS reflection were simulated using the TEM Floquet port with 3-D electromagnetic simulation software, namely, CST. Reflection simulations of a unit cell for normal incidence were carried out according to the polarization given in Figures 2 and 5b. For the more accurate simulation in the 3-D simulated model, the rectangular dielectric slab with the varactor package size, shown in Figure 5a,b in green, was defined with an effective varactor package dielectric constant \(\varepsilon_{\mathit{eff}}\). The value of the effective dielectric constant was \(\varepsilon_{\mathit{eff}}=6\) based on our previous work, with a good agreement to the experimental results [18]. The dissipation resistivity of the unit cell \(R\) was composed of \(R_{\mathit{did}}\) and \(R_{\mathit{ohm}}\), which were the intrinsic dielectric and ohmic losses, respectively; \(R_{S}\), which was the varactor serial resistance; and \(R_{P}\), which related to inaccuracies and parasitics in the manufacturing process. The values of \(R_{\mathit{did}}\) and \(R_{\mathit{ohm}}\) were well defined and quantified in CST simulation, while the \(R_{S}\) value was not provided in the datasheet, and the \(R_{P}\) value depends on the manufacturing process quality and not only on the unit cell's inherent properties. The MS experimental measurements were carried out using two wideband 4 to 40 GHz, double-ridge horn antennas, model PowerLOG 40400, from the Aaronia Company. The two antennas were placed at about 60 cm perpendicular to the MS, one as a transmitter Tx and the other as a receiver Rx. The Tx and Rx antennas were connected to a Vector Network Analyzer (VNA) from the Keysight Company, model P9375A. The measurement setup is shown in Figure 9.  
Figure 9 shows the measurement setup with the arrangement of the antennas and the MS prototype. The Tx's vertical height was lowered and tilted relative to the MS center. The Rx's vertical height was raised and tilted relative to the MS center to avoid radiation blockage between the Tx and the Rx. The MS columns were uniformly set with DC voltage or capacitance values for extracted unit cell reflection properties. The unit cell reflection simulation results for the max and min capacitance values compared to the measurement results for 0 V and 16 V reverse bias voltages are shown in Figure 10.  
In Figure 10, the unit cell reflection simulation results as a function of frequency in dashed lines for \(C_{\mathit{max}}=0.216\) pF and \(C_{\mathit{min}}=0.033\) pF were compared to the measurement results in continuous lines for varactors reverse bias voltages of 0 V and 15 V, respectively. The MS reflection results were normalized to a copper plane surface reflection of the same size. The MS reflection results were normalized to a copper plane surface reflection of the same size. The \(f_{\mathit{res}}\) value could be controlled along the entire X-band and the low Ku-band from 7.8 to 15 GHz, depending on the \(C_{d}\), providing an almost 100% \(f_{\mathit{res}}\) tuning and maximum dynamic reflection phase range of 323\({}^{\circ}\) and over 300\({}^{\circ}\) in the entire X-band. Figure 9: The reflection measurement setup. Thus, the MS reflection allowed for wide bandwidth and significant continuous change in the reflection phase. The resistance values of \(R_{S}+R_{P}\) were considered in the simulation for each \(C_{d}\) value. The values of \(R_{S}+R_{P}\) in the simulation results were 19 \(\Omega\) and 10.5 \(\Omega\) for \(C_{max}\) and \(C_{min}\), respectively. The simulation results showed good agreement with the measurement results. Furthermore, compared to our previous work with the same varactor diode in which the \(R_{S}+R_{P}\) values were about 7.5 \(\Omega\) for all \(C_{d}\) capacitance values [18] and compared to another work where the resistance value was 8.5 \(\Omega\) based on the panel [46], it was shown that not all the measured resistance was related to the varactor, namely, \(R_{S}\).