**6. Conclusions**

In conclusion, a dual-band high PCR cross-polarization converter is designed, fabricated and measured. This design is inspired by the concept of transmitarray. The cross-polarized transmittance is higher than 0.9 at 10.37 GHz and 11.71 GHz. The co-polarized transmittance is significantly suppressed below 0.005, which leads to an almost perfect PCR. Thus, the transmitted wave has an extremely high polarization purity. In addition, by varying *a* and *w*, the two working frequencies can be tuned independently. The presented design represents a basis for the development of transmissive metasurfaces for wavefront control by changing the length of the stripline on layer-3. The proposed design also can be used for transmissive linear-to-circular polarization converter by using a truncated square patch on the layer-5 instead. The proposed cross-polarization converter can be employed in antenna, radar or telecommunication applications.

**Author Contributions:** Conceptualization, S.H.; methodology, J.L. and F.J.; validation, J.L.; formal analysis, J.L. and F.J.; investigation, F.J. and H.S.; resources, A.Z.; data curation, B.L.; writing—original draft preparation, H.S.; writing—review and editing, H.S.; visualization, J.L. and F.J.; supervision, J.L. and J.C.; project administration, J.C., A.Z. and H.S.; funding acquisition, J.L.

**Funding:** This research was funded by National Natural Science Foundation of China gran<sup>t</sup> number 61871315, in part by Technology Program of Shenzhen gran<sup>t</sup> number JCYJ20170816100722642, JCYJ20180508152233431 and in part by the Natural Science Foundation of Guangdong Province, China gran<sup>t</sup> number 2018A030313429. The APC was funded by 61871315.

**Conflicts of Interest:** The authors declare no conflict of interest.
