Investigation ff Microstrip Patch Antenna Using Complementary Split Ring Resonators for Wireless Applications

Abstract

Microstrip has emerged as the most revolutionary antenna technology ever. Microstrip patch antennas (MPAs) are preferred over other antennas in today’s scenario for their compatibility to be fit in mobile, aircraft, satellites owing to very small sizes. Hence design and development of superior and cost effective MPAs has become an active research area. Moreover, considerable development work in the field of MPAs has been going on in trying to meet the increasingly demanding systems requirements such as size miniaturization, improved bandwidth, multifrequency operations etc. This thesis work focuses mainly on design and analysis of MPA using metamaterial. Metamaterials are the artificial materials engineered to impart properties which may not be easily procurable in nature. These materials generally inherit their properties from structure instead of composition, utilizing the inclusion of slight inhomogeneities to accomplish effective macroscopic behaviour. The metamaterial used in this thesis work is Complementary Split Ring Resonator (CSRR). A CSRR is a highly conductive structure in which the capacitance between the two rings balances its inductance. When time-varying electric field is applied parallel to the rings surface, it induces currents which, in dependence on the resonant properties of the structure, produce a magnetic field that may either oppose or enhance the incident field, thus resulting in positive or negative effective є. The presented work includes designing and simulation of two designs, one having coplanar rectangular MPAs with slotted CSRR in the ground plane and other without slotted CSRR. The effect of CSRR inclusion on different parameters such as return loss, bandwidth and mutual coupling has been studied. The simulation results confirm that slotted CSRR shows significant reduction of return loss along with improvement in the bandwidth. In addition, reduction in the mutual coupling between two antenna elements has been observed, thereby making the structure suitable for minimizing coupling and co-channel interference in multiband antennas. The research work also includes simulation of a dual band MPA with two side-by-side CSRR structures on a single patch fed by a microstrip line covering the two WLAN bands in 2.4 (2.4–2.484 GHz) and 5.2 (5.15–5.35 GHz). The dimensions of the complementary ring elements as well as microstrip feed-line width have been varied for required resonant frequencies and return loss characteristics. Simulated results including current distribution and radiation pattern have been analysed. This design has been extended for a multiband MPA which consists of two open-circuited stubs added on each side of the antenna along

with two side-by-side CSRR structures on a single patch. The suggested antenna finds applications in various wireless systems since it covers different IEEE standards which include WLAN bands in 2.4 (2.4–2.484 GHz) and 5.8 (5.725–5.825 GHz), Bluetooth (2.4-2.5 GHz) and WiMAX bands of (2.5-2.69 GHz and 5.25-5.85 GHz) and X-band satellite downlink (7.25 GHz-7.75 GHz).. The designed antenna has been simulated using the commercially available software CST Microwave Studio 2010. With the help of the simulated results, various parameters like return loss, gain, directivity, VSWR and bandwidth have been discussed. The multiband antenna has been fabricated and the fabricated antenna has been tested in VNA (Vector Network Analyser). Finally, the simulated results have been compared with measured results obtained from the fabricated antenna.