Microstrip Antenna Gain Enhancement using Near Zero Refractive Index Metamaterials

Some useful features of microstrip patch antennas are low profile, low weight and easy fabrication. However this type of antenna suffers from having a low gain, caused by propagation surface waves. In this paper, a new near zero refractive index metamaterial (MTM) unit cell is designed and fabricated as a superstrate over a Rectangular Microstrip Patch Antennas (RMPA). In order to obtain a maximum gain, the distance between the superstrate and the microstrip of the antenna has been optimized. Additionally, the feed position has been optimized to minimize the return loss. The operation frequency set at 10.3GHz and there are two resonance frequencies, one at 10.1GH and the other one at 11.68GHz. The simulations and measured results indicated that the superstrate MTM structure, designed to place horizontally over the antenna, increases the gain to almost 2.4dB and 2.62dB at 10.1GHZ and 11.68GHZ respectively. Moreover, the radiation efficiency and directivity of the antenna are improved significantly.