A Compact Circularly Polarized Antenna Based on Metasurface

This paper designs a circularly polarized antenna based on metasurface for internet of things (IOT) applications. The proposed antenna includes two parts, a 4x4-unit mushroom metasurface plane, and cross-shaped slot feeding structure. The metasurface is designed by adjusting the dispersion curve of a unit cell. According the composite right/left hand transmission line (CRLH-TL ) theory, negative 1st order mode is expected in the metasurface. The corss-shaped slot on the defected ground is coupled by a meander microwave line. Thus, the metasurface is excited the -1<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">st</sup> mode at 2.5 GHz with left hand circular polarization. The whole dimension of the antenna is (45×45×3.8 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>) at 2.5 GHz, and the simulated -10 dB impedance bandwidth is from 2.16 GHz to 2.8 GHz with 25.6% fractional bandwidth. The maximum realized gain is 4.1 dBic and it has a broad side radiation pattern. This compact circular polarization antenna is a competitive candidate for IOT applications.