Single-layer circular polarizer using metamaterial and its application in antenna

In this letter, we report a new type of circular polarizer using a single-layer metamaterial. The unit cell is composed of a metallic annular-ring and an embedded strip. Numerical and experimental results show that the linearly polarized plane wave can be converted to circularly polarized wave with a 3-dB axial ratio bandwidth of about 17%, which is from 13.25 to 15.7 GHz. The polarizer can also keep good circular polarization with incident off-normal angle in the range of +/- 30 degrees. Subsequently, this polarizer is applied in the linearly polarized microstrip patch antenna as superstrate, making this antenna composite radiate circularly polarized wave. In addition, the antenna gain is enhanced by about 3 dB in comparison with conventional patch antenna without polarizer. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:17701774, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26884