Analytical and experimental study of gain enhancement in antenna arrays covered with high index metamaterial superstrate

Antenna arrays are used in communication applications where directive beams are required.In this article, we show analytically and experimentally that the gain of an antenna array can be further increased by covering it with a high refractive index superstrate. For the experimental demonstration, a corporate-fed 4 x 1 microstrip patch array is fabricated and the electromagnetic pattern measurements are performed on the array covered with a magneto-dielectric metamaterial. A fast analytical solution for the radiation fields of the superstrate-covered microstrip antenna array is also proposed. The analytical solution is based on the reciprocity theorem in conjunction with the transmission line analogy and the cavity model. The artificial superstrate is designed using broadside coupled split ring resonator inclusions and is placed at approximately one-tenth of a wavelength apart from the patch array operating at 2.2 GHz. A directivity increase of about 3.4 dB is achieved after covering the antenna array with the engineered magnetic superstrate. A comparison of results using the analytical model, the full-wave simulations and measurements show good agreement. The proposed analytical formulation requires only 2.5% of the time required by full-wave analysis. The superstrate-based directivity enhancement method can be used in commercial antennas to combat some of the downsides of the existing systems such as gain decrease due to surface waves and dielectric losses. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:215218, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27261