A Multifunctional Patch Antenna Loaded with Near Zero Index Refraction Metamaterial

In this paper a multifunctional patch antenna loaded with near zero index refraction metamaterial (NZIM) is presented. This multifunctional antenna operates at 5.8 GHz and provides high gain and beam steering capability. The proposed configuration comprises a patch antenna placed below an NZIM superstrate. The rectangular microstrip antenna is used as a radiation source to demonstrate the performance of this design. The NZIM superstrate, which behaves as an NZIM, based on 9 x 9 resonating unit cells of split ring resonators (SRRs), allows gathering radiated waves from the antenna and collimating them toward the superstrate's normal direction, which results in gain enhancement. The beam-steering in the E-plane is obtained by slowly tilting the NZIM over the patch antenna. The main characteristics of the antenna placed near the NZIM superstrate are studied numerically and experimentally to successfully demonstrate this dual function feature. It is found experimentally that the gain enhancement of 8 dB with improved directivity and radiation efficiency are obtained in comparison with the antenna without the NZIM metasurface. In addition, we were also able to steer the direction of the main beam just by tilting the NZIM superstrate from -20 degrees to 20 degrees. with a gain variation of 5 dB and without changing the whole dimension of the structure.