Design and Analysis of Fractal Antennas for wideband Apllications

Abstract

The use of fractal geometries has significantly impacted many areas of science and engineering; one of which is antennas. Antennas using some of these geometries for various telecommunications applications are already available commercially. The use of fractal geometries has been shown to improve several antenna features to varying extents. Wide band fractal antennas geometry has been proposed in this thesis. Fractal shapes and their properties are discussed. The proposed antennas are microstrip line fed and their structure are based on fractal geometry where the resonance frequency of antenna is lowered by applying iteration techniques. The bandwidth was optimized by combining different geometries resulting in a hybrid Fractal Antenna. Analysis of fractal antenna was done by using the Software named CST Microwave Studio Suite 12. This antenna has low profile, lightweight and easy to be fabricated and has successfully demonstrated wideband characteristics. The first Fractal antenna is based on the Koch curve geometry. It is operating in a wideband frequency range of 3.31-7.84GHZ hence giving a bandwidth of 81.26% and achieves an efficiency of 83.2% with a peak Gain of 3.66 dB. The second proposed Fractal antenna is a modified version of the 1st one and has a wide operating bandwidth of 85.37% from 3.31-8.4GHz.The antenna achieves an efficiency of 87.6% with a peak Gain of 3.05dB.The third proposed antenna is a Hybrid Fractal antenna that achieves an efficiency of 86.7% and has a peak gain of 3.4dB. It has a bandwidth of 85.05% from 3.3-8.18GHZ.The proposed antennas exhibit omnidirectional radiation behaviour. The measured bandwidth meets the requirements of many commercial bands such as WI-FI 802.11y (3.6-3.7GHZ), WiMAX (3.4-3.6 GHZ and 3.7-4.2 GHZ) and WLAN 802.11(5.31-6.32GHZ).