172 research outputs found
Design of nanostructured metamaterials in METACHEM
No full textIt is my pleasure to present the publication Nanostructured Metamaterials – Exchange between experts
in electromagnetics and material science.
Metamaterials are one of the new discoveries of the last decade. They present exceptional properties,
dominated by their geometrical structure and this publication will allow the reader to learn more about
these ‘artificial’ materials and about their interesting (and yet unexploited) potential applications. The design
and manufacturing of such materials has been made possible thanks to progress made in both materials
science and electrical engineering. With the help of bottom-up manufacturing techniques, a large number
of micrometer scale designs can now being scaled down to nanometer scale and therefore completely
new solutions can be investigated. The tools needed to create metamaterials include modelling, geometry
and property design, bottom-up manufacturing and structural and electron microscopy characterization
at the atomic- and nano-scale. By controlling the reactivity of atoms and molecules to create inclusions
and by controlling the positioning of these nano-inclusions, nanostructured metamaterials can been realised
with interesting fields of applications where waves are involved, such as ICT applications and noise reduction.
The 7th Framework Programme for Research (FP7), the European instrument for funding scientific research
and technological development up to 2013, is targeting synergy between traditional scientific disciplines
and this resulted in fostering four bottom-up manufacturing projects and a coordinated action on
characterisation of metamaterials. Their total budget is EUR 20M with a FP7 contribution of EUR 15M.
A workshop has been dedicated to metamaterials in December 2009 and its main outcome is presented
in this publication.
So often materials are the bottleneck or, positively, the enabler for technological progress resulting in
novel and sustainable products made available to all citizens. Within the larger family of industrial technologies,
material science and engineering show paramount potential to allow such progress with benefits for
industry and the society as a whole.
Metamaterials had a current market size of EUR 133 million in 2007 and are expected to grow to EUR 2.1 billion
in 2013 (1), a compound annual growth rate (CAGR) of 26.5 %. I hope that the interdisciplinary and creative
collaboration between material scientists and engineers together with ICT researchers will support this
growth by allowing secure understanding and rapid progress in the innovative field of metamaterials, as this
would allow exploiting their industrial (and later on, commercial) potential to the benefit of European
industrial growth and the creation of jobs.
Renzo Tomellini
European Commission
Head of Unit ‘Value-added Materials
A Quasi-Direct Method for the Surface Impedance Design of Modulated Metasurface Antennas
No full textA new approach is presented for synthesizing modulated metasurface (MTS) antennas (MoMetAs) with arbitrary radiation patterns, assumed to be given in amplitude, phase, and polarization. The MTS is defined on a circular domain and is represented as a continuous sheet transition impedance boundary condition (IBC) on the top of a grounded substrate. The proposed method relies on an entire-domain discretization of the electric field integral equation (EFIE). Via the dyadic Green's function of the grounded substrate, the desired radiation pattern is translated into the visible part of the surface current spectrum, decomposed into entire-domain and orthogonal basis functions, while the invisible part of the spectrum stems from the solution of the unmodulated sheet problem. The EFIE is then inverted to obtain the sheet impedance, which is constrained to be anti-Hermitian, as required for implementation with lossless patches. The efficiency of the method relies on the precomputation of the reaction integrals between three functions: basis functions for currents and impedances and testing functions for fields. The formulation is presented first for the scalar (isotropic) MTS case and then generalized to the tensorial (anisotropic) MTSs. Several radiation patterns are presented and designed successfully. A full-wave method-of-moment code is used to validate the designed MTSs IBC
Efficient numerical analysis of 3D periodic metamaterials: Multilayer approach and eigenmode analysis
No full textModeling the electromagnetic behaviour of metamaterials is a challenge that is still being addressed. The computation of the propagative modes inside the materials is necessary to understand the way periodic structures interact with electromagnetic fields and to develop methods to characterize them. In this paper, we present a numerical method based on the PMCHWT formulation of the Method of Moments for the analysis of 3D metamaterials. Exploiting interstitial equivalent currents between different layers of the medium, it is possible to study its bulk properties simulating only one slab. Moreover, all the eigenmodes of the structure can be computed at once with a great accuracy
Stereoscopic and velocimetric reconstructions of the free surface topography of antidune flows
No full textMetasurface Antennas: Efficiency versus Bandwidth
No full textTwo methods are proposed for the accurate and fast analysis of the efficiency of arbitrarily modulated metasurface (MTS) antennas. The surface current on the MTS is expanded into entire-domain basis functions. The first method uses a Fourier-Bessel basis and relies on the Poynting theorem, while the second approach is based on the calculation of the surface-wave residue with a Gaussian-Ring expansion for the current. Both methods allow one to compute the efficiency of MTS antennas in a few minutes, which represents a drastic reduction of the computation time in comparison with any commercial software. The algorithms are then used to analyze the frequency dependence of the efficiency of MTS antennas in two different cases: 1) anisotropic MTS with uniform periodicity, 2) anisotropic MTS with non-uniform periodicity. The latter case corresponds to an active region MTS and provides a larger bandwidth. Validation with commercial software and measurements data is provided
Foreword (Editorial)
No full textIt is our great pleasure to present the Proceedings of the 15th International Conference on Ground Penetrating Radar (GPR 2014), held in Brussels, Belgium, from June 30 to July 4, 2014. The International Conference on Ground Penetrating Radar is a longstanding traditional event making the premier forum of research and applications in the field of GPR. GPR 2014, the 15th in the series that has been held biannually since 1986, has brought together high-standard scientists, engineers, industrial delegates and end-users working in all GPR areas, ranging from fundamental electromagnetics to the so various fields of application. Topics covered include novel developments of GPR systems and antennas, advanced data processing algorithms for improved subsurface imaging, radar data modeling approaches and inversion strategies for quantitative reconstruction of soil and material properties, and finally, data interpretation in a range of fields, including geology and sedimentology, glaciology, environmental and agricultural engineering (e.g., hydrological monitoring, digital soil mapping, forestry), civil and military engineering (e.g., utility detection, monitoring of transport infrastructures, nondestructive testing, landmine detection), archeology and cultural heritage, and planetary exploration, among others. GPR 2014 is in particular co-organized with EU-COST (European Cooperation in Science and Technology) via the Cost Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar”. [cont.
Power balance and efficiency of metasurface antennas
No full textThis paper presents two methods for the efficient evaluation of the power balance in circular metasurface (MTS) antennas implementing arbitrary modulated surface impedances on a grounded dielectric slab. Both methods assume the surface current in the homogenized MTS to be known. The first technique relies on the surface current expansion with Fourier-Bessel basis functions (FBBF) and proceeds by integration of the Poynting vector on a closed surface. The second method is based on the evaluation of the residue of the electric field spectrum at the surface-wave (SW) pole, and is demonstrated by using a current expansion in Gaussian ring basis functions (GRBF). The surface current expansions can be directly obtained either by analyzing the antenna with a Method of Moments (MoM) tool for homogenized MTSs based on FBBF or GRBF, or derived by a projection process. From there, the power contributions, namely the total power delivered by the feed, the radiated power, the SW power, and the Ohmic power losses in the dielectric are computed. Several efficiency metrics are presented and discussed: tapering efficiency, conversion efficiency, loss factor, and diffraction factor. Since the MTS apertures at hand are leaky-wave (LW) antennas, the designer must find a compromise between the aperture efficiency and the conversion efficiency. This requires accurate and fast computational techniques for the efficiency. The present paper demonstrates for the first time that the efficiency of MTS antenna devices can be accurately evaluated in a few minutes. The compromise that should be made during the design process between the tapering efficiency and the conversion efficiency is highlighted. The impact on the efficiency of isotropic versus anisotropic MTS, uniform versus non-uniform modulation index, is analyzed. An excellent agreement is obtained between both approaches, commercial software, and experimental data
Statistics of the MLE and approximate upper and lower bounds-Part I: Application to TOA estimation
No full textIn nonlinear deterministic parameter estimation, the maximum likelihood estimator (MLE) is unable to attain the Cramér-Rao lower bound at low and medium signal-to-noise ratios (SNRs) due the threshold and ambiguity phenomena. In order to evaluate the achieved mean-squared error (MSE) at those SNR levels, we propose new MSE approximations (MSEA) and an approximate upper bound by using the method of interval estimation (MIE). The mean and the distribution of the MLE are approximated as well. The MIE consists in splitting the a priori domain of the unknown parameter into intervals and computing the statistics of the estimator in each interval. Also, we derive an approximate lower bound (ALB) based on the Taylor series expansion of noise and an ALB family by employing the binary detection principle. The accuracy of the proposed MSEAs and the tightness of the derived approximate bounds are validated by considering the example of time-of-arrival estimation
An ultra-wideband battery-less positioning system for space applications
No full textAn ultra-wide bandwidth (UWB) remote-powered positioning system for potential use in tracking floating objects inside space stations is presented. It makes use of battery-less tags that are powered-up and addressed through wireless power transfer in the UHF band and embed an energy efficient pulse generator in the 3-5 GHz UWB band. The system has been mounted on the ESA Mars Rover prototype to demonstrate its functionality and performance. Experimental results show the feasibility of centimeter-level localization accuracy at distances larger than 10 meters, with the capability of determining the position of multiple tags using a 2W-ERP power source in the UHF RFID frequency band
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