DESIGN AND ANALYSIS OF FRACTAL ANTENNA FOR UWB COMMUNICATION AND BIOMEDICAL APPLICATIONS

Abstract

Various characteristics of fractals have been used in making antennas for a very long time. Fractal geometries have made it possible to use a single antenna for various applications due to its wideband and multiband property, as it maximizes the effective length of the antenna without any use of inductors or capacitors.

Multiband Fractal antenna designs have been proposed in this thesis. Analysis of fractal antenna was done by using the software named Ansys HFSS 15.0. Antenna simulated showed multiband characteristics with compact, light-weight, and easy to fabricate the design. The first antenna is based on Sierpinski Gasket geometry. It operates in a multiband frequency range of 4.1- 10.9 GHz and 20.7-33.4 GHz. The second antenna is based on Sierpinski Carpet geometry. It operates in a multiband frequency range of 5.2-6.4 GHz, 7.6- 11.3 GHz, and 19-30.9 GHz. The third antenna is based on Koch curve geometry. It operates in a multiband frequency range of 4.6- 11.1 GHz and 20.8-28.1 GHz. Biomedical implantable antenna using fractals have been designed which requires properties like compact size, low specific absorption rate, flexibility, and wideband characteristics. For proper positioning of the antenna inside the human body, the size of the antenna must be small. Various techniques are used for the miniaturization of the antenna, including concentric ring slots in the shape of a rectangle. Flexibility is another requirement for the implantable antenna. This prevents the breakage of the antenna with any movement of the body part of the muscle. Thin and flexible layers of substrate and superstrate are used to provide flexibility. Also, these layers should be biocompatible. The antenna is covered with a thin layer of biocompatible material to enhance its performance by reducing the absorption in the lossy environment. A reduced antenna gain has been observed due to the absorbing nature of the human body. So, to improve the antenna gain, different techniques are used, namely external parasitic ring and hemispherical lens along with the encapsulation layer around the antenna.