Innovative Techniques for Antenna Synthesis in Modern Wireless Communication Systems

This thesis deals with the study and development of innovative techniques for the synthesis of antennas able to fulfill the tight requirements of modern wireless communication systems. By exploiting the advantages given by the use of geometries based on spline and fractal shapes, the aim of the proposed synthesis techniques is the design of small Ultra-Wideband (UWB) and multi-band antennas. The synthesis of UWB antennas is carried out by means of two different approaches which consider the antenna characterization in the frequency and in the time domain, respectively. The antenna structure is based on a spline representation which allows the description of complex contour by means of a limited set of control parameters. Regarding the synthesis of multi-band antennas, an approach based on the perturbation of fractal geometries is proposed. The perturbation breaks the fixed relationships among resonances typical of standard fractal geometries, allowing the use of fractal antennas for practical applications. By exploiting the knowledge acquired during the synthesis of UWB spline-shaped antennas, a preliminary assessment of an approach for the design of multi-band antennas with spline-based geometries is also reported. Finally, the integration of UWB antennas in array layouts is addressed. Towards this end, first a methodology for the design of aperiodic UWB linear arrays populated by spline-shaped radiating elements is proposed. Successively, the design of an array of UWB elements for imaging applications is described. In order to assess the effectiveness as well as the reliability of the proposed antenna synthesis approaches, both numerical and experimental results are reported.