Novel and Compact Reconfigurable Antennas for Future Wireless Applications

Abstract

The development of reconfigurable antennas is considered to be very promising in modern and future communication systems. Reconfigurable antennas have made use of many reconfiguration techniques that are centred upon switching mechanisms such as p-i-n diodes or MEMS. Other techniques such as optical switches, mechanical structure changing or the ability to change the permeability or permittivity of smart substrate materials have also been used. Reconfigurable antennas have created new horizons for many types of applications especially in Cognitive Radio, Multiple Input Multiple Output Systems, personal communication systems, satellites and many other applications. Cognitive Radio is one of the potential wireless applications that may place severe demands on RF systems designers and particularly antenna designers, when it comes to providing exible radio front-ends capable of achieving the set objectives of the technology. The aim of this work is to investigate possible roles that different categories of reconfigurable antenna can play in cognitive and smart radio. Hence, the research described in this thesis focuses on investigating some novel methods to frequency-reconfigure compact ultra-wideband antennas to work in different bands; this will offer additional filtering to the radio front-end. In the ultra-wideband mode, the antenna senses the spectrum for available bands with less congestion and interference and hence decides on the most suitable part to be reconfigured to, allowing reliable and efficient communication links between the radio devices. Ultra-wideband antenna with reconfigurable integrated notch capability is also demonstrated to provide further enhancement to interference rejection and improve the overall communication link. Furthermore, the design of novel pattern and polarisation reconfigurable antennas will be also investigated to assist Cognitive Radio through spatial rather than frequency means. An ultimate target for this research is to combine different degrees of reconfiguration into one compact, state of the art antenna design that meets the growing demand of cognitive and smart radio devices for more intelligent and multi-functional wireless devices within the personal area network domains and beyond.