## 5 Conclusions  
In summary, a broadband polarizer was here presented using single-layered transmissive metasurfaces that can perform conversion operations in dual bands (11.05-16.75 GHz, 34.16-43.03 GHz: Ku/Ka band). The structure can perform transmission polarization conversion over a broad range of frequencies (bandwidths of 41% and 23%) for dual bands. It can convert linearly polarized waves into right-hand circularly polarized waves in the Ku band and left-hand circularly polarized waves in the Ka band. To validate the design strategy, a sample of the proposed polarization converters consisting of an array of 30 \(\times\) 30 unit cells was fabricated. Measurements were performed using free-space characterization techniques with a VNA and two sets of linearly polarized antennas. Simulated and measured results were coherent, which shows that the polarizer had remarkable performance in the polarization conversion operation. Such converters can be potentially applied for miniaturization and polarization control. Moreover, its polarization conversion performance using a single-side layered structure in dual bands may have diverse applications in wireless communication systems, including multiple-channel operations.  
The proposed dual-band polarizer integrated with a separate feeding structure can be used in different scenarios, such as vehicles on the move, communication systems, and satellite communication systems. Since the design is a universal design, the polarizer can be redesigned to operate in any frequency band of operation for integration with dual-band LP array structures to produce dual-band CP waves. In the future, tunability will be introduced using external controlling mechanisms. For example, controllable circuit elements, state-changing materials, and structural changing scenarios in the polarizers could result in reconfigurable dual-band polarizers.  
Writing--original draft preparation, A.K.F., writing--review and editing, A.K.F., C.R. and R.N., methodology, A.K.F., software, A.K.F., validation, R.N. and C.R., supervision, C.R., project administration, C.R. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China, grant number 61831001.  
Not applicable.  
The study did not report any data.  
The authors declare no conflict of interest.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Ref**} & **Frequency of** & **Operational** & **No. of** & **Operational** & **Stability** \\  & **Operations (GHz)** & **Bandwidth (\%)** & **Layers** & **Modes** & **with Change** \\ \hline
[21] & 19.6, 29.6 & 4, 2.7 & 3 & Same & - \\ \hline
[23] & 19.95, 29.75 & 2.5, 1.7 & 3 & Orth. & 30\({}^{\circ}\) \\ \hline
[24] & 7.6, 13 & 31.6, 13.8 & 4 & Same & \(\pm\)25\({}^{\circ}\) \\ \hline
[25] & 17.8, 36.5 & 25, 16.4 & 2 & Orth. & - \\ \hline
[31] & 20.6, 29.2 & 12.5, 8.7 & 6 & Orth. & \(\pm\)45\({}^{\circ}\), \(\pm\)30\({}^{\circ}\) \\ \hline
[28] & 18.5, 28.5 & 24, 11 & 2 & Orth. & - \\ \hline This work & 13.9, 38.59 & 41, 23 & 1 & Orth. & \(\pm\)45\({}^{\circ}\), \(\pm\)30\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table}
Table 2: Performance comparison with other state-of-the-art dual-band polarization converters (LC-to-CPs).