International Journal of Innovative Technology and Exploring Engineering (IJITEE) ISSN: 2278-3075 (Online), Volume-8 Issue-12, October 2019 496 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: L3387081219/2019©BEIESP DOI: 10.35940/ijitee.L3387.1081219 Journal Website: www.ijitee.org Abstract: A Near Zero refractive Index (NZIM) metamaterial inspired UWB circular antenna as a superstrate for gain and directivity improvement’s is presented and investigated in this work. The frequency range with S 11 less than -10dB is from 4.5GHz to 12.5GHz. The permeability and permittivity of the (NZIM) has an extraordinary property that could be optimized to synchronously approach zero and have an effective wave impedance matching with air and near-zero index simultaneously, this feature of metamaterial gives the NZIM the ability to collimates the incident bending waves and gather it’s towards the normal direction. Hence the antenna performances in term of the gain and directivity will be enhanced. The studied metamaterial design is optimized and analyzed using CST microwave. Obviously, the antenna gain and directivity are enhanced by 4.8 and 4.89 respectively. The simulation of this developed metamaterial antenna has been optimized and performed by using Computer Simulation Technology- Microwave Studio (CST) and Ansof High Frequency Structure Simulator (HFSS). Keywords: Near Zero Index Metamaterial, Gain, Directivity, UWB circular antenna. I. INTRODUCTION In recent years, several metamaterials inspired the microwave device have been developed and used to improve their performance especially antennas [1],[2] .In 2002, Enoch et al, investigated the metamaterial and found that using the near zero index (NZIMs) as a superstrate could achieve the directive emission on antenna. Backward Cerenkov radiation, simultaneously negative permeability and permittivity, negative index, backward wave, and so on are the most attractive extraordinary properties of metamaterials [3]. The near-zero index metamaterials (NZIM) have a kind property that can control the antenna radiation wave and gather it to be in a normal direction, to more clarify the principle procedure, Revised Manuscript Received on October 30, 2019. * Correspondence Author Mourad Elhabchi*, LASTID Laboratory, Department of physics, Faculty of Sciences, Ibn Tofail University ,Kenitra, Morocco .Email mouradelhabchi@hotmail.fr Mohamed Nabil Srifi, Electronics and Telecommunication Systems Research Group, National School of Applied Sciences (ENSA), Ibn Tofail University, kenitra, Morocco. Email srifimn@ieee.org Raja Touahni, LASTID Laboratory, Department of physics, Faculty of Sciences, Ibn Tofail University ,Kenitra, Morocco . © The Authors. Published by Blue Eyes Intelligence Engineering and Sciences Publication (BEIESP). This is an open access article under the CC-BY-NC-ND license http://creativecommons.org/licenses/by-nc-nd/4.0/ we will use the Snell’s law, when the ray is incident from inside the NZIM into free space, the angle of refraction will be normal to the interface because the refracted rays will be controlled and closed to near zero. As a result, the metamaterial will improve the antenna performance in terms of gain and directivity [4]. To extract the S-parameters from CST to MATLAB software’s, the computation method using Nicolson Ross algorithm was used for retrieving the permeability, permittivity and refraction index of metamaterial. Some metamaterial antennas have been implemented and studied [5], an anisotropic ZIML was theoretically presented with proper design 2016, A near-zero index metamaterial lens as superstrate and an Artificial Magnetic Conductor (AMC) substrate are used respectively to improve the antenna directivity and to reduce the height of a low profile antenna. An improved gain with good impedance matching based on ZIMLS of Vivaldi The antenna is studied in [6]. The gain of bow-tie antenna is increased by The ZIMLS property used the split ring resonator (SRR) array is presented in [7]. A Fabry-Perot resonant cavity (FPRC) is another technique to increase the antenna gain, it is obtained using a frequency selective surface (FSS) or an electromagnetic band-gap (EBG). A metamaterial using the frequency selective surfaces (FSSs) superstrate on the top side of a metallic ground plane containing a compact antenna are also used and implemented. In this paper, an UWB circular compact monopole antenna [8] which is suffering from a low directivity and gain is inspired as superstrate with a one layer metamaterial unit cell near zero refractive-index layer (NZIM). From the obtained results, both the gain and directivity of the proposed design are effectively increased respectively by 4.8dB and 4.89dB using the mentioned technique based on metamaterial. Finally, an antenna performance comparison between the conventional small circular UWB antenna the modified proposed loaded metamaterial UWB circular antenna is presented as well as a comparison with recently similar works[9]. II. ANTENNA DESIGN PROCEDURE The design geometry together with dimensions of the reference low gain circular UWB antenna without MTM superstrate is illuminated in Fig. 1. A Metamaterial Inspired UWB Circular Antenna as Superstrate for Gain and Directivity Improvement’s Mourad Elhabchi, Mohamed Nabil Srifi, Raja Touahni