Asymmetric Chiral Metamaterial Superstrate for Patch Antenna Polarization Transformation

Planar superstrates constituted by Chiral Metamaterials structures can transform the radiation properties of an antenna. In this communication, an asymmetric chiral metamaterial based structure is proposed. Due to the lack of C4 symmetry in the design, the transmission coefficients depend on the incident wave polarization and display high transmission for one circular polarization but low transmission for the other one. The proposed structure is then used to improve the radiation characteristics of a microstrip patch antenna. Taking advantage of the properties of the asymmetric chiral structure, the polarization of the radiated field is modified, transforming the linear polarization of the microstrip antenna into a circular one.