DESIGN OF ULTRA WIDEBAND ANTENNA WITH TUNABLE NOTCH

Abstract

Ultra wideband communications area has been growing since the opening of 7.5 GHz frequency spectrum from 3.1-10.6 GL-lz because of its many inherent advantages such as high data rate, consumption of less average power, decreased vulnerability to multipath cancellation, higher range measurement accuracy and range resolution, low cost. UWB is a game changing technology to achieve huge data rates. New technologies call for new improvements. UWB technology poses many challenges on the design of antennas. The aim of this thesis is to design, implement and analyze the performance of compact printed UWB antennas which uses Coplanar Waveguide (CPW) feeding mechanism with tunable notch. First, a UWB antenna has been designed and analyzed for its efficacy. Then the UWB antenna designed has been modified to produce a notch at upper Wireless Local Area Network (WLAN) 91 band (5.725-5.825 GHz). Finally tunability of notch frequency in 5-6 GHz has been attained using varactor diode. Several bandwidth increment techniques used in designing UWB antennas have been outlined. An amalgamation of the bandwidth increment techniques has been used in designing the proposed UWB antennas. The designed antennas have been studied extensively using designed parameters with regard to their effect on antenna's performance. All the proposed antennas printed on 24 mm x 30 mm FR4 substrate have an impedance bandwidth covering the whole UWB band, show omnidirectional radiation characteristics, gain less than 5 dBi over the whole UWB band. The performance parameters required to analyze UWB antennas have been calculated for UWB antenna, UWB antenna with notch, namely Group delay, Ringing duration and System Fidelity Factor. The calculated results show that the designed antennas produce very less dispersion of the input signal. The experimental and numerical results of the designed antennas in frequency domain and time domain show that the proposed antennas satisfy all the requirements for use in portable UWB devices.