## 3 Simulation and Analysis
Interestingly, an additional advantage of the proposed structure is that it maintains its conversion performance when an incident vertical (y-polarized) wave is applied as an incident wave. However, this time, the resulting outgoing polarization sense is reversed; i.e., there is an RHCP and LHCP for the 11.05-16.75 GHz range (Ku band) and 34.16-43.03 GHz range (Ka-band), respectively (as shown in Figure 2d-f). Since the structure of the proposed polarizer is uni-layered, it can be insensitive to large changes in incident angles. Usually, while operating in transmission modes, such converters need to bear these changes and sustain performance for oblique incident angles. To investigate this, the unit cell was analyzed in Ansys HFSS using the change in incident angles of the applied TE wave, and the response variation in terms of the axial ratio was also analyzed. The results are presented in Figure 3 in steps of 10\({}^{\circ}\) from 45\({}^{\circ}\) to \(-\)45\({}^{\circ}\). It is clear that the polarizer performed equally well in the first band of operation (Ku band), which is a remarkable achievement for a transmission-based polarizer. For the second frequency band of operation, the performance in the lower half of the operational band remained unchanged, except for a small frequency shift. However, the polarization conversion performance degraded greatly for \(\pm\)45\({}^{\circ}\) in the operational frequency band higher than the center frequency of band. This performance remained good for \(\pm\)30\({}^{\circ}\) changes in incident angles. Thus, the proposed conversion performance remained stable for \(\pm\)45\({}^{\circ}\) for the first band of operation and \(\pm\)30\({}^{\circ}\) for the second band. To explain the physics behind linear to circular polarization conversion, surface current vectors were monitored at different time intervals: t = 0, t = T/4, t = T/2, t = 3T/4, with T being the time period for the incident wave at resonant frequency. Figure 4a-d show surface current vectors at 13.58 GHz, whereas Figure 4e-h show surface current vectors at 40 GHz. Figure 4a shows that, at t = 0, the resultant surface current vectors at the unit cells were directed at an angle of 270\({}^{\circ}\) from the +x-axis. For ease of understanding, we represent the magnitude of these vectors at the center with the help of a blue line, with an arrowhead showing the direction of surface currents. Figure 4b shows that, at t = T/4, the surface current vectors lay along the -x-axis, manifesting a rotation of 90\({}^{\circ}\) from t = 0. At t = T/2, the  
Figure 3: Simulated response for oblique incidences. Figure 2: Simulated transmission response for the proposed metasurface with incident horizontal (x)polarized wave: (**a**) transmission component; (**b**) phase difference; (**c**) axial ratio. Simulated transmission response with incident vertical (y)polarized wave: (**d**) transmission components; (**e**) phase difference; (**f**) axial ratio (AR). angle changed to 90\({}^{\circ}\) along the x-axis. For t = 3T/4, the surface current vectors were aligned with the x-axis, hence forming an angle of 0\({}^{\circ}\) along the x-axis. Thus, increasing the time interval by T/4 results in further rotations of the surface current vectors by an angle 90\({}^{\circ}\). This rotation of the current vectors was clockwise, meaning the outgoing wave was an RHCP wave; it is also well-explained electrically in Section 2, Figure 2b. Similarly, surface current vectors for other operational band at the center frequency of 40 GHz are represented in Figure 4e-h at different time intervals. In these figures, it is clear that, with every time duration of T/4, the rotation of surface currents is 90\({}^{\circ}\) counter-clockwise, resulting in an LHCP transmitted wave, as explained electrically in Figure 2e.