INVESTIGATIONS ON WIDEBAND AND MULTIBAND FRACTAL SLOT ANTENNA DESIGNS

Abstract

In recent years, slot antennas have gained a wider popularity. Presently, the trend is to design highly efficient, high gain, compact, wideband and broadband antennas for modern wireless communication systems, which require greater capacities, secure and high-speed transmissions. Therefore, wideband antennas are required. Printed and slot microstrip antennas are widely used in high data rate wireless communication systems. They exhibit a low profile, small size, light weight, low cost, high efficiency, and ease of fabrication and installation. Furthermore, they are generally economical to produce because they are readily adaptable to hybrid and monolithic integrated circuits' fabrication techniques at RF and microwave frequencies. For antenna designers, fractal geometries have presented myriad exciting opportunities because of the unique electrical properties they exhibit. The space filling capabilities and self-similar properties of fractals have a paramount importance to design compact, multiband and wideband antenna elements. Ideally, high performance antennas can be designed by combining the unique features of fractals and slot structure. This dissertation presents design of fractal geometry based wideband slot antennas. The analysis tool used for the success of the work is high frequency structure simulator —HFSSv11 based on the finite element method. Different fractal geometry based coplanar waveguide(CPW) fed slot antennas are designed: dual band wide slot antenna with Bowtie-shaped tuning stub based on Sierpinski gasket, Wideband Sierpinski gasket based wide slot antenna, Wideband Hilbert curve based slot antenna, ultra wide band Koch snowflake based wide slot antenna and ultra wideband Sierpinskigasket based wide slot antenn.The performance characteristics of each antenna types are studied theoretically and compared with the experimental results. Each antenna type is designed to operate at wideband of frequencies after extensive parametric study is performed on HFSS. For the efficient simulation and time management, a Matlab code is developed for each fractal geometry to generate coordinate points recursively and to export them directly to the electromagnetic simulator-HFSS. Matlab and HFSS interact through port communication using a simple code developed in matlab