Linear to circular polarization converter using ultrathin and Bi-functional metasurface

An ultrathin linear to circular polarization converter based on bi-functional metasurface is designed for simultaneous manipulation of reflection and transmission polarization conversion. The unit cell consists of a square ring and a central slant dipole loaded with two U-shaped stubs. The simulated results demonstrate that the proposed converter can transform the x(y)-polarized incident wave into left(right)-handed circularly polarized wave in the reflection mode, whereas into right(left)-handed circularly polarized wave in the transmission mode. Compared with other polarization converters, the proposed design can simultaneously provide reflection and transmission polarization conversion with opposite rotational directions in the range of 24.58–26.64 GHz. Besides, the angular stability of 3 dB axial ratio is up to 45° for two different working modes in the frequency range of 24.58–25.18 GHz. Furthermore, this design is built on a single metallic layer and a substrate in thickness 0.254 mm, making it easier to be fabricated and integrated. The experimental results demonstrate a good agreement with simulated ones. It is envisaged that the metasurface provides a new avenue for applications in polarization-controlled devices and microwave communications.