Predavanje "Retrieval of Constitutive Parameters in Metamaterials"

Abstract:
The amazing interest on metamaterials, which has been growing for a decade, has in parallel posed a lot of questions about the most reliable and accurate approach to the characterization of their electromagnetic behavior.  Most of the metamaterials can be described as a periodic repetition of some inclusions in a host medium; the inclusions can be made resonant despite their small dimension in terms of a wavelength. It is well accepted in various scientific communities to consider this type of artificial structures as effective media, described by a set of equivalent constitutive parameters. These parameters can be obtained by using analytical models, measurements or full-wave simulations in conjunction with numerical retrieval algorithms. However, the procedure for the definition of the equivalent parameters is not univocally defined, and different approaches may be used depending on the metamaterial characteristics and on the goal of the homogenization process. The analysis methodologies for retrieval of constitutive parameters include those based on a microscopic-equivalence and those based on a macroscopic-equivalence. The former set up a model relating each element of the periodic arrangement to an equivalent particle with electric and/or magnetic dipolar moment. This requires constituent particles small in terms of a wavelength, since the response of the single particle is approximated by the dominant term of a multi-polar expansion. On the other hand, macroscopic-equivalence approaches identify equivalent wave impedance and propagation constant for the field propagating inside the metamaterial, and they look for a homogeneous medium supporting the same modal structure. In this case the restrictions on the electrical size of the inclusion may be less severe, and it is possible to correctly retrieve the scattering parameters from a metamaterial sample. However, there could be some intrinsic ambiguities in the extraction of the equivalent parameters. In this lecture, after the review of the literature, an original method of retrieval of the metamaterial constituent parameters is described, with emphasis on removing ambiguity and on the role played by the spatial dispersivity of the constituent parameters. The special class of metamaterials formed by periodic multilayer arrangements of 2D printed structures will be considered with much attention. Anisotropy and special case of gyrotropy, as well as bianisotropy and the special case of chirality will be considered in the parameter retrieval.

CV:
Stefano Maci is a Professor the University of Siena (UNISI), with scientific responsibility of a group of 15 researchers (http://www.dii.unisi.it/~lea/).  He is the Director of the UNISI PhD School of Information Engineering and Science, which presently includes about 60 PhD students. His research interests include high-frequency and beam representation methods, computational electromagnetics, large phased arrays, planar antennas, reflector antennas and feeds, metamaterials and metasurfaces. Since 2000, he was responsible of 5 projects funded by the European Union (EU); in particular, in 2004-2007 he was WP leader of the Antenna Center of Excellence (ACE, FP6-EU) and in 2007-2010 he was International Coordinator of a 24-institution consortium of a Marie Curie Action (FP6). He also carried out several projects supported by the European Space Agency (ESA-ESTEC), the European Defense Agency (EDA), the US-Army Research Laboratory (ARL), and by various industries and research institutions: EADS-MATRA, (Toulouse, France), IDS (Pisa, Italy), TICRA (Copenhagen, Denamrk), ALENIA MARCONI SYSTEM (Rome, Italy), SAAB-ERICSON SPACE (Gotheborg, Sweden), THALES (Paris, France), TNO (Hague, The Netherlands), OTO MELARA (La Spezia, Italy), OFFICINE GALILEO (Florence, Italy), SELEX Communication (Rome, Italy), Thales Alenia Space (Rome, Italy).
Since 2001 he was a member the Technical Advisory Board of 11 international conferences, member of the Review Board of 6 International Journals; in the same period, he organized 23 special sessions in international conferences, and he held 10 short courses in the IEEE Antennas and Propagation Society (AP-S) Symposia about metamaterials, antennas and computational electromagnetics. He was an Associate Editor of IEEE Trans on EMC and of IEEE Trans. on AP and two times Guest Editor of special issues of the latter journal. In 2003 he was elected Fellow of IEEE. In 2004 he founded the European School of Antennas (ESoA), a PhD school that presently comprises 30 courses on Antennas, Propagation, Electromagnetic Theory, and Computational Electromagnetics. ESoA counts about 150 among the best teachers of Europe (which include eleven IEEE Fellows) and it is frequented by an average of 220 students per year. The ESoA consortium presently comprises 33 European research centers and offers 12 one-week courses per year.
In 2005-2007, he was Italian National representative of the NATO SET-TG 084 "Emerging Technology for Sensor and Front-ends”, and he is presently involved as co-representative in the NATO SET-181 RTG on "Metamaterials for Defense and Security Applications".
Stefano Maci was co-founder of two spinoff-companies and since 2008 he is honorary President of LEAntenne e Progetti SPA (Valeggio sul Mincio, VE).
Stefano Maci is presently Director of ESoA, a member of the Board of Directors of the European Association on Antennas and Propagation (EuRAAP), a member of the Technical Advisory Board of the URSI Commission B, a member elected of the AdCom of IEEE Antennas and Propagation Society, a member of the Governing Board of the European Science Foundation (ESF) Project “NewFocus”, a member of the Governing board of the FP7 coordination action “CARE” (Coordinating the Antenna Research in Europe), a member of the Award Committee of the IEEE Antennas and Propagation Society (AP-S), a member of the Antennas and Propagation Executive Board of the Institution of Engineering and Technology (IET, UK), and a member of the Focus Group on METAMATERIALS in the Finmeccanica project “Mind-Share”.  
His research activity is documented in 10 book chapters, 110 papers published in international journals, (among which 76 on IEEE journals), and about 300 papers in proceedings of international conferences. His h index is 24, with a record of more than 2000 citations (source Google Scholar).