Odjel za teoriju i primjenu mikrovalova (MTT), Odjel za antene i širenje elektromagnetskih valova (APS), Zajednički odjel AES i GRS, Zavod za radiokomunikacije Fakulteta elektrotehnike i računarstva, Znanstveni centar izvrsnosti za znanost o podatcima i kooperativne sustave te Odjel komunikacijskih sustava HATZ pozivaju vas na predavanje:
"Higher symmetries for the design of periodic structures"
koje će održati Dr. Oscar Quevedo-Teruel s KTH Royal Institute of Technology, Stockholm, Švedska u utorak, 5. prosinca 2017. godine, u 14:00 sati, u Sivoj vijećnici Fakulteta elektrotehnike i računarstva, zgrada D – prizemno.
Sažetak predavanja i životopis predavača nalaze se u nastavku obavijesti.
Periodic structures possess twist symmetry when their lattice is created by a translation and an angular rotation. If the angular translation is 2-fold, the angular movement becomes a mirroring, and the higher symmetry is named glide. Both glide and twist symmetries are higher-symmetry periodic structures.
Higher symmetries were intensively studied in the ‘60s and ‘70s, especially for the case of propagation in 1D periodicities, which were employed to produce leaky wave antennas. Recently, the study of higher symmetries is again an active research topic in the fields of microwave technology, antennas and metamaterials. For example, it has been recently demonstrated that 2D glide-symmetric structures can be employed to produce low dispersive equivalent refractive indexes. These periodic unit cells can be used to produce ultra-wide band lens antennas.
Additionally, glide-symmetric structures have demonstrated to be able to produce low-cost gap waveguide technology. Glide-symmetric configurations have a similar bandgap as the conventional bed of nails, but they require holes that are typically thicker, and with a high tolerance in variations of their height dimensions.
Due to these interesting properties, efficient methods to analyze these higher symmetry periodic structure are important. Commercial software based on MoM, FEM or FDTD lead to slow solutions due to the different scales of the structures, i.e., large structures with small dielectric gaps. For the 1D periodic cases, two methods has been proposed: mode matching and circuit models. Both of them are much faster than commercial software while achieving a perfect agreement. Circuit-model analysis is typically faster, but have limitations in terms of geometric parameters. For the 2D geometries, only mode matching techniques are available at the moment.
In this presentation, I will introduce the concept of higher symmetries, including both glide and twist symmetries. We will describe the remarkable properties of higher symmetries, such as their ability to produce both large bandgaps and low dispersive media. Higher-symmetry structures provide a new degree of freedom for the design of periodic structures, and find potential application for bandgap waveguide technology, ultra-wideband flat lenses, and low-dispersive leaky wave antennas.
Oscar Quevedo-Teruel received his M.Sc. degree in Telecommunication Engineering from Carlos III University of Madrid Spain, and went on to complete his Master of Engineering at Chalmers University of Technology in Sweden. He obtained his PhD from Carlos III University of Madrid in 2010 and was then invited into a postdoctoral research position at the University of Delft (The Netherlands). From 2010-2011, Dr. Quevedo-Teruel joined the Department of Theoretical Physics of Condensed Matter at Universidad Autonoma de Madrid as a research fellow, and went on to continue his postdoctoral research at Queen Mary University of London from 2011-2013. In 2014, he joined the School of Electrical Engineering (EES)/Electromagnetic Engineering (ETK) at KTH Royal Institute of Technology in Stockholm Sweden where he is an Assistant Professor.
Dr. Quevedo-Teruel was the recipient of the Award of Excellence in 2010 from Carlos III University of Madrid. In 2010, he also received the National Award of Arquimedes for the best supervisory of M. Sc. Theses in Engineering and Architecture throughout Spain. Recently, in 2012, he received the prestigious Raj Mittra Junior Travel Grant.
Dr. Quevedo-Teruel has made significant scientific contribution to higher symmetries (glide and twist), transformation optics, lens antennas, metasurfaces, leaky wave antennas, metamaterials, multi-mode microstrip patch antennas and high impedance surfaces. He is the co-author of more than 45 papers in international journals, two book chapters, more than 100 at international conferences and has received approval on 2 patents.
More information can be found in this webpage: http://www.etk.ee.kth.se/personal/oscarqt/