IJSRD || National Conference on Inspired Learning || October 2015 ©IJSRD 2015 Published by IJSRD 90 A Metamaterial based Microstrip Patch Antenna with Improved Directionality Nitin Kumar 1 Anumeha Badoni 2 Pravesh Belwal 3 Ranjita Singh 4 Sandeep Sharma 5 S. C. Gupta 6 1 Assistanr Professor 2,3,4 M. Tech Scholar 1,2,3,4,5,6 Department of Electronics and Communication Engineering 1,2,3,4,5,6 DITU, Dehradun Abstract— This paper focuses on improving the directive properties of a conventional patch antenna by using a known technique of applying metamaterial slab as a cover. The metamaterial under consideration is a modification of Pendry‟s SRR structure and is equivalent to two SRRs connected back to back. The unit cells were arranged in an array configuration, investigation of S- parameters was done for checking the Negative index property. As expected with the use of metamaterial as a cover, directionality of conventional patch antenna improved significantly and the 3 dB beam-width reduced. A conventional patch antenna generally shows 3 dB beam-width of ~80deg while the antenna presented in this paper with the metamaterial shows improved 3dB beam-width of 45 deg. Key words: HFSS, Patch Antenna, Metamaterial, Reduced Beam-Width I. INTRODUCTION Recently, there has been a growing interest in the field of metamaterials both theoretically and experimentally. Metamaterials are artificial materials engineered to have properties that may not be exhibited by its own constituting materials. In 1968 V. G. Veselago first proposed the idea of metamaterials with simultaneously negative values of dielectric permittivity and magnetic permeability [1]. However positive permittivity and permeability are the basic properties of conventional materials available in nature known as Double positive (DPS) materials. Metamaterials are termed as Double negative (DNG) materials due to the property of negative permittivity and permeability [2-4]. A microstrip patch antenna (MSA) in its simplest form consists of a radiating patch on one side of a dielectric substrate and a ground plane on the other side. Radiation from the MSA occurs from the fringing fields between the radiating patch and the ground plane. Deschamps first proposed the concept of MSA in 1953 [5] and practical MSA was developed by Munson and Howell in the 1970s [6]. The MSA offers numerous advantages for various applications which include low weight, small volume and ease of fabrication [7]. However MSAs suffer from some disadvantages also as compared to conventional microwave antennas such as narrow bandwidth, lower gain and broad beam-width. In recent years increasing interest has been focused on the use of metamaterials for improving the performance of conventional patch antennas [8-9]. A quick literature survey shows that DNG Materials can be used for directivity enhancement, radiated power enhancement, antenna performance improvement and bandwidth enhancement of the conventional patch antennas. In this paper work is done in order to reduce the beam-width and thus improve the directionality of a conventional patch antenna. The structure of the metamaterial unit cell is covered in [10], and in this paper unit cells of the metamaterial structure are combined to form an array to be used as a cover for reduction of 3 dB beam-width of patch antenna at 14 GHz. II. PROPOSED STRUCTURE A. Metamaterial- Figure 1 shows a unit cell of the proposed structure. It consists of 2 Split ring resonators connected back to back and a rectangular strip. It has been shown in various papers that a single SRR provides magnetic resonance and supports negative effective permeability. The split ring resonator (SRR) structure is printed on a dielectric substrate of thickness 0.9 mm and dielectric constant 5.7 (mica). Radius of the outer and inner ring of the SRR is 2.9 mm and 2.7 mm respectively. The length and width of the rectangular strip are taken as 5.4 mm and 0.2 mm respectively. The unit cell is simulated by HFSS by using PEC and PMC boundary conditions. The PEC boundary conditions are applied to those surfaces which are perpendicular to incident electric field vector whereas the PMC boundary conditions are applied to the surfaces perpendicular to the incident magnetic field vector. Two waveguide ports were set at the top and bottom of the Z- axis, where the wave penetrates the material [10-11]. Fig. 1: Metamaterial Unit Cell