A study and design of frequency-notched planar UWB antennas with reconfigurable functionality using PIN diodes

Abstract

This dissertation is a report of the work carried out in the design of microstrip planar antennas for Ultra-wide bandwidth (UWB) applications. It is divided into three broad sections as follows: The first section (chapters 1, 2 and 3) is concerned with an investigation of designs and results reported in technical literature. It also includes the design of a novel antenna. This design was underpinned by three important constraints: -10 dB bandwidth across the whole UWB spectrum (3.1 to 10.6 GHz), dimensions small enough to ease its integration in small portable devices, and low manufacturing costs (by adopting a simple design and using a cheap substrate). In the second section (chapter 4) the various frequency notching techniques in existence are reviewed and reported. It then continues to report the modification carried out on the antenna, designed in the first section, in order to render it frequency selective. The technique applied for frequency selectivity is more aptly referred to as frequency notching, as the band of frequencies to be selected (or rejected) is only 0.68 GHz wide. The method used for frequency notching is a new one, developed in this work and not encountered in the literature reviewed. The final section (chapters 5 and 6) deals with reconfigurability techniques. These techniques adopt a switching element (usually this is a MEM device or PIN diode), included on the antenna, which is switchable, by an electrical bias, such that the antenna's configuration is subtly modified thereby rendering it reconfigurable (and frequency dependent). The concluding chapter puts forward recommendations for possible future work.