A NOVEL CPW FED SUPER WIDEBAND HEPTAGONAL FRACTAL MONOPOLE ANTENNA

Abstract

Miniaturization has become a requirement of modern wireless systems. Majority of applications require low profile and wideband antennas. The reduction in size of antenna decreases its efficiency. Fractal shape antennas present the solution to design wideband and compact antennas without compromising the antenna efficiency. The Fractal geometry with properties like self similarity, jagged shapes, long electrical lengths provide the benefits of multiband behavior, effective radiation and miniaturization. Many Fractal geometries are available for wideband applications. The investigation of conventional fractal shapes like Koch, Minkowski, Sierpinski, Pythagorean Tree structures is made to find out new Fractal shapes. Ultra wideband (UWB) technology presents many advantages like immunity to multipath interference, security, low interference and high data rates. Antenna for UWB applications requires wideband impedance matching characteristic and compactness. This requirement resulted in a trend to design wideband and compact antennas for wireless systems. Long electrical lengths of patches are encapsulated in a small area which reduces efficiency. Fractal antennas present solution for designing compact and wideband antennas. Available fractal geometries for wideband applications are Sierpinski, Koch, Minkowski and Pythagorean tree. Various polygonal shape antennas are designed in HFSS to find desired polygonal geometry with wideband property. Proposed solution with heptagonal fractal antenna gives desired performance. Thesis work presents a comparison of novel heptagonal fractal monopole antenna design for two different substrates. A super wideband heptagonal fractal monopole antenna with coplanar waveguide feed is designed and fabricated. Fractal geometry has base shape of heptagon. Base shape is iterated four times. FR4 and Rogers RT/ Duroid 5880 substrates are used for antenna design and fabrication. Monopole configuration of antenna provides omni-directional radiation pattern. Simulated and measured results analysis shows that monopole fractal antenna with Rogers RT/ Duroid 5880 substrate has better performance than fractal antennas fabricated on FR4 substrate.