Some studies on designs of planar antennas for UWB applications

Abstract

In Ultra-Wideband (UWB) wireless system, considerable research efforts have been put into the design of UWB antennas and communication systems. These UWB antennas are essential for providing wireless wideband communications based on the use of very narrow pulses on the order of nanoseconds, covering a very wide bandwidth in the frequency domain and over very short distance at very low power densities. Also it is well known that, in traditional narrow-band communications, multiple antenna systems offer attractive aspects in wireless communication by means of Multiple-Input Multiple-Output (MIMO) techniques. These techniques either give out high channel capacities through spatial multiplexing, or offer an increase of link robustness. The present work deals with four new compact broadband antennas, suitable for portable applications are designed and characterized, namely-octagon shaped monopole, semicircular disk monopole, semi-octagon shaped diversity, semi-circular diversity. The performances of these designs have been studied using standard simulation tools used in industry or academy and experimentally verified. One of the major contributions of the thesis lies in the analysis of the frequency and time-domain response of the designed UWB antennas to confirm their suitability for portable pulsed-UWB system. A technique to avoid narrow band interference by etching narrow slot resonators on the antenna is also proposed and their effects on a nano-second pulse have been investigated.