Improvement of the gain and the axial ratio of a circular polarization microstrip antenna by using a metamaterial superstrate

In this article, a new design of circular polarized (CP) microstrip antenna for 2.2 GHz band applications is introduced. This compact design has achieved return loss and axial ratio lower than -10 and 3 dB, respectively. Next, a polarized insensitive metamaterial surface acting as a superstrate is proposed for improvement of the antenna characteristics. By putting the suggested double stacked meta-surface layer over a CP microstrip antenna, the radiation pattern of antenna has been improved significantly. As a result, the antenna gain is enhanced about 4.7 dBi and simultaneously the overlap of return loss band and axial ratio band is increased about 3%. The structure is simulated in CST MICROWAVE STUDIO software and the results show reasonable conformity with the measurements.