Small Antenna Design Challenges

Bio

Ala Sharaiha received the Ph.D. and Habilitation à Diriger la Recherche (HDR) degrees in telecommunication from the University of Rennes 1, France, in 1990 and 2001 respectively. Currently, he is a Full Professor at the University of Rennes 1 and the Co-Head of the Antennas and Microwave Devices Department at the IETR research Laboratory (Institute of Electronics and Telecommunications in Rennes). He has graduated/mentored more than 40 Ph.D. students/postdocs and co-authored with them. He has authored or co-authored more than 450 journal and conference papers, concerning antenna theory, analysis, design and measurements. He holds 12 patents. His published works have been cited over 2000 times in Google Scholar. His current research interests include small antennas, broadband and UWB antennas, reconfigurable antennas, printed spiral and helical antennas, absorbers, innovative materials for antennas and antennas for mobile communications.

He is presently a French delegate member of the European Association on Antennas and Propagation (EuRAAP) and a member of the small antennas working group of EuRAAP. He is a senior member of the IEEE and is a reviewer for the IEEE APS, IEEE AWPL, the IET Letters and the IET Microwave Antennas Propagation. He was the conference Chairman of the 11th International Canadian Conference ANTEM (Antenna Technology and Applied Electro-Magnetics), held at Saint-Malo in France, 2005.

Abstract

The rapid evolution in the wireless communication systems requires more miniaturization of various electronic components in addition to the major element of the wireless technology: the antenna. In this case, an antenna occupying a limited space should be miniaturized in order to operate at the desired communication bands. The performance in terms of bandwidth, gain and so on for these antennas is extremely critical and is governed by fundamental limitations in size, i.e. Chu’s limit. Classical size reduction techniques with material loading and geometry shaping of the antenna suffer from narrow bandwidth and low radiation efficiency. On the other hand, attempts to increase the directivity of small antennas using superdirective arrays are also associated with low radiation efficiency and very narrow bandwidth.

The recent state-of-the art in the field of miniature antennas shows new perspectives for the development of compact antennas presenting directivities higher than accepted normal limits (super-directivity properties) as well as large bandwidth behavior.

By combining the characteristic mode analysis with an optimization algorithm, it becomes possible to optimally manipulate the currents inside the antenna to achieve wideband, superdirective and efficient designs. This presentation gives some results and examples on improving performances of electrically small antennas.