APPLICATION OF METAMATERIALS FOR PERFORMANCE ENHANCEMENT OF PLANAR ANTENNAS

Abstract

The ever growing communication system industry and the development of the communication techniques in the last one decade have thrown great challenges to microwave engineers to enhance the performance of the existing systems to cope up with the new wireless communication standards. Antennas, considered as the backbone of the wireless communication system, have to function at par with the other subsidiary microwave circuitry. In this regard, the challenges faced by the antenna engineers are to enhance the performance of the antennas and at the same time to shrink the size of the antenna system. As planar antennas are preferred mostly in wireless industry, because of some of its advantages like light weight, flexibility, conformability etc., constant efforts have been made to enhance its performance, since its inception. The research done in this thesis is an attempt in that direction and the metamaterial concept is used for the performance enhancement of planar antennas. The pioneering work by Veselago in 1968, followed by Pendry in 1996 has made the foundation of the metamaterial concept and since then this artificial material has been adopted by microwave engineers for various activities. Antenna engineers are not exceptions and have used this material for many antenna applications. A glance over the related literature reveals that, most of the works are either results from the full-wave simulators or experimentally verified structures. An analytical approach for metamaterial based planar antenna was absent from the literature. An attempt has been made in this thesis to develop an analytical model and to find out a closed-form expression for the resonant frequency of a metamaterial based planar antenna. Although a specific type of metamaterial (CSRR) structure is used for the analysis, but the same can be extended for other structures also. After attempting the analysis problem, the design aspect of such structures was explored. The aim was to develop a fast, user-friendly module to fix the design dimensions of metamaterial based antennas, for it to work at desired frequency. The task was approached as an optimization problem and with the help of machine learning approaches, was solved successfully. In order to validate the working of the developed module, few typical cases were considered. The rest of the work done in this thesis is to use different metamaterial structures IV to overcome some of the drawbacks of simple patch antennas. Design of simple multiband patch antennas, enhancement of directivity and design of compact planar antenna structures are the works attempted in this thesis. Laboratory prototype of almost all the antenna structures is made and experimentally measured for cross-verifying the results from the analysis or from the full-wave simulators. Although some specific metamaterials are used in this thesis, but the concepts developed can be extended to other structures also, giving a scope for future research work. The authors are sure that the work done in this thesis will certainly help the antenna community in a big way.