Search

Nowadays, there exists a tendency for replacing typical metallic materials in the aerial platforms for nonmetallic ones. However, this arises many questions, for example, how they react against Electromagnetic Enviromental Effects (E3), where we can count lightning effects among many others. Due to this, the aim of this work is to characterize different type of joints commonly used in the aerospace industry for Carbon Fiber Composite (CFC) fuselages. This analysis is crucial in order to figure out possible electrical discontinuities that could affect to the electromagnetic behaviour of an aircraft. Having that in mind, a flexible measurement setup based on a microstrip line is proposed, where different CFC test samples are evaluated. This research was funded by the Spanish Ministry of Science and Innovation (MICINN) under the project eSAFE-DAV (PID2019-106120RB-C32). Preprint

The tendency over the last decades in the aerospace industry is to substitute classic metallic materials with new composite materials such as carbon fiber composites (CFC), fiber glass, etc., as well as adding electronic devices to ensure the safety and proper platform operation. Due to this, to protect the aircraft against the Electromagnetic Environmental Effects (E3), it is mandatory to develop accurate electromagnetic (EM) characterization measurement systems to analyze the behavior of new materials and electronic components. In this article, several measurement methods are described to assess the EM behavior of the samples under test: microstrip transmission line for a surface current analysis, free space to obtain intrinsic features of the materials and shielding effectiveness (SE) approaches to figure out how well they isolate from EM fields. The results presented in this work show how the different facilities from the National Institute of Aerospace Technology (INTA) are suitable for such purposes, being capable of measuring a wide variety of materials, depending on the type of test to be carried out. This research was funded by the Spanish Ministry of Science and Innovation (MICINN) under project eSAFE-UAV (PID2019-106120RB-C32). Peerreview

[ES] Se pretende diseñar un panel "user firendly" para la caracterización de materiales (permitividad) con sondas coaxiales. Se programarán diferentes procedimientos de caracterización disponibles en la bibliografía

The growth of the application of electronic devices has created a new form of pollution known as noise or radio frequency interference, electromagnetic radiation, or electromagnetic interference (EMI), which results in the malfunction of equipment. A new carbon-based polymer composite has been unlocked through the discovery of polymer composites. Carbon nanotubes (CNTs) have shown potential as reinforcement fillers in polymer to enhance an EMI shielding material owing to their large specific surface area, well-defined 3D networking structure, and unique electronic structure. The main focus of this review is the role of CNT as fillers in intrinsic conducting polymer and conducting polymer composite. The factors that influence EMI shielding performance are also included in this review. The roles of the size; shape; and electronic, mechanical, and chemical properties of nanomaterials in tuning the EMI shielding effectiveness of polymer hybrid are emphasized. The structural design of CNT polymer composite has been reviewed as well. Future research direction has been proposed to overcome the current technological limitations and realize the most advanced EMI shielding materials for future use. The composites have a potential to replace traditional shielding materials owing to their advantageous properties.

It is increasingly common in aerospace industries to take advantage of novel composite materials in their manufacturing processes to improve performance and reduce costs. Obtaining the electromagnetic (EM) characterization of these materials or a combination of them is essential to ensure safety and EM compatibility.In this paper, a laminate of the central fuselage of an aircraft developed at INTA is recreated. This aircraft is called MILANO and it is mostly made of Carbon Fiber Composite (CFC). The same material is used for the laminate. Besides, another metallic plate is built in order to compare the performance of the former one with respect to a Perfect Electric Conductor (PEC). The main goal of this work is studying the coupling between the cable bundles embedded in the MILANO and how is this affected by the different materials of the ground plate (metal and CFC). Two kind of tests are carried out: S-parameters measurents and injection of Lightning Indirect Effect (LIE) waveforms. S-parameters results are then obtained through simulation too and compared with both the metallic and the CFC sample. The work described in this paper has been funded by the Spanish Ministry of Science and Innovation (MICINN) under projects UAVE3 (TEC2016-79214-C3-1-R) and eSAFE-UAV (PID2019-106120RB-C32). Peerreview

Metamaterials are materials with exotic characteristics that do not exist in nature. They can be made by a periodic metal structure whose elementary cell is quite small compared to the wavelength at the frequencies of interest. From an electromagnetic point of view, these materials can in particular have a negative permeability at certain frequencies. On the other hand, a low pressure plasma can be modeled as a material with negative permittivity if its electron density exceeds the critical density at a specific frequency. This thesis studies the integration of a negative permeability metamaterial, the Split Ring Resonator (SRR), into a low pressure argon plasma (between 5 and 100 mTorr). The objectives are, on the one hand, to produce a reconfigurable metamaterial based on plasma as a controllable element and, on the other hand, to produce a doubly negative material, also known as a left-hand material, presenting both a permittivity and a negative permeability. The approach was experimentally conducted using a metal cavity where a 13.56 MHz Inductively Coupled Source (ICP) was placed over the cavity (isolated by quartz glass) for ignition and the maintenance of the plasma. Inside this cavity two horn antennas have been fixed for the microwave characterization. A dedicated characterization method, specific to this complex environment, has been developed to electromagnetically characterize the created structure. A Langmuir probe was used to measure the electron density of the generated plasma. Electromagnetic simulations are made using the ANSYS Electronics Desktop(r) tool to help understand the effects of plasma on the SRR metamaterial and its resonance., Les métamatériaux sont des matériaux possédant des caractéristiques exotiques qui n'existent pas dans la nature. Ils peuvent être réalisés par une structure métallique périodique dont la cellule élémentaire est assez petite devant la longueur d'onde aux fréquences d'intérêt. D'un point de vue électromagnétique, ces matériaux peuvent notamment avoir une perméabilité négative à certaines fréquences. D'autre part, un plasma à basse pression peut être modélisé comme un matériau à permittivité négative si sa densité électronique dépasse la densité critique à une fréquence spécifique. Cette thèse étudie l'intégration d'un métamatériau à perméabilité négative, le Split Ring Resonator (SRR), dans un plasma d'argon à basse pression (entre 5 et 100 mTorr). Les objectifs visent d'une part, à la réalisation d'un métamatériau reconfigurable à base du plasma comme élément contrôlable, et d'autre part, à la réalisation d'un matériau doublement négatif, connu aussi sous le nom de matériau main gauche, présentant à la fois une permittivité et une perméabilité négative. La démarche a été menée de manière expérimentale à l'aide d'une cavité métallique où une source à couplage inductive (ICP) à 13.56 MHz a été placée au-dessus de la cavité (isolée par une vitre du quartz) pour l'allumage et l'entretien du plasma. A l'intérieur de cette cavité deux antennes cornets ont été fixées pour la caractérisation microonde. Une méthode de caractérisation dédiée, spécifique à cet environnement complexe, a été développée pour caractériser électromagnétiquement la structure créée. Une sonde de Langmuir a été utilisée pour mesurer la densité électronique du plasma généré. Des simulations électromagnétiques sont faites en utilisant l'outil ANSYS Electronics Desktop(r) pour aider à comprendre les effets du plasma sur le métamatériau SRR et sa résonance.

Modern aircraft employ profusely carbon fiber composites (CFC) for their construction. Then, it is mandatory to characterize the behaviour of this kind of materials for its use under harsh electromagnetic environments. In that sense, this paper presents the application of two standards, the ASTM D4935 and the IEC 61000-4-21, to the measurement of the shielding effectiveness (SE) of aeronautical multi-ply CFC laminates frequently used for the construction of aircraft. Each technique is well suited for a specific material or realization and a specific frequency range. So, both techniques are complementary and should be developed in parallel. Taking into account the high SE expected for this kind materials, the set-ups imply the measurement of very low signals, that poses an experimental challenge that has to be faced. Then, in this study, different test samples and realizations of CFC materials have been fabricated and measured. Improvements on the traditional measurement procedures have been applied, obtaining promising results. This work has been funded by the Spanish Ministry of Science (MCIU) under project UAVE3 (TEC2016-79214-C3-1-R). Preprint

The rigorous electromagnetic characterization of passive UHF radio frequency identification (RFID) tags is a challenging task. Among various solutions, in a previous work, an automatic tool for the over-the-air evaluation of significant RFID tag metrics has been presented. Once the distance is fixed, the system, based on the estimation of the minimum power emitted by the off-the-shelf interrogating reader capable to energize the tag under test, exhibits an accuracy that, although adequate, is affected by the minimum power step at the reader side. In this communication, an evolution of a new platform whose working principle has already been introduced by the same authors is presented. It is based on an analytical model opportunely derived to overcome this limit while preserving flexibility and cost-effectiveness. The platform can automatically vary with continuity the interrogation distance - which becomes a new degree of freedom - and it is able to estimate the couple power distance for each frequency, which practically annuls the estimation error due to the power discretization. Moreover, the enhanced system now allows for a pretest phase that is useful to verify whether or not the implemented analytical model is valid in the specific environment, even if not electromagnetically anechoic. © 1963-2012 IEEE.

Following the development of the new electronic systems and communication networks, the levels of electromagnetic contamination have risen dramatically in the recent years. Every day, new studies appear searching for a way to mitigate the electromagnetic interferences (EMI). At the same time, the rapid evolution of technology forces the field to search for lighter and more efficient materials. The composites using carbon allotropes (such as carbon nanotubes) and polymers as reinforcement are gaining importance, due to the many advantages they exhibit in comparison to the materials that were used until now. A great number of applications require absorption to be the main electromagnetic shielding mechanism, thereby making this review necessary as a way to summarize the latest studies on CNT/polymer composites and how to improve the absorption mechanism by changing the morphology and composition of CNTs. This work was supported by the grant Nanoarq (MAT2014-57557-R) from the Spanish Ministerio de Ciencia e Inovación.

We report the fabrication and electromagnetic characterization of a planar composite metamaterial (CMM) that is designed to achieve dual-frequency double-negative response at the lower end of the extremely high-frequency (EHF) band. The CMM is based on cut wire pairs and continuous wire elements. Dual-frequency operation is obtained by employing cut wire pairs of two different lengths within the unit cell of the CMM. The magnetic response of the cut wire pairs and the left-handed transmission band of the CMM are demonstrated by experiment and numerical simulations. It is found that the combined electric response of the dual-band CMM is complicated and imposes certain restrictions to the structure design in achieving true left-handed response at both designated frequencies. © 2006 IEEE.

Made available in DSpace on 2019-09-12T16:26:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2009 Resumo: Materiais Absorvedores de Radiação Eletromagnética (MARE) são compostos que absorvem a radiação eletromagnética incidente em determinadas faixas de frequências e a dissipam sob a forma de calor. Esses materiais são obtidos a partir do processamento adequado de matrizes poliméricas incorporadas com compostos que atuam como centros absorvedores da radiação incidente, na faixa de micro-ondas. Este trabalho mostra a avaliação eletromagnética de MARE processados pelo uso de uma hexaferrita de cálcio modificada pela incorporação dos íons CoTi e La. A substituição realizada pelos íons mencionados mostra, via análises de MAV, que a ferrita apresenta baixos valores de magnetização de saturação (123,65 Am2/kg) e de campo coercitivo (0,07 T), indicando o seu amolecimento. Amostras de MARE preparadas com diferentes concentrações desta hexaferrita (40 - 80% em massa) apresentam mudanças nos parâmetros complexos de permeabilidade e permissividade e no desempenho da atenuação da radiação incidente. Valores de atenuação da radiação incidente entre 40 e 98% são obtidos. Abstract: Radar Absorbing Materials (RAM) are compounds that absorb incidental electromagnetic radiation in tuned frequencies and dissipate it as heat. Its preparation involves the adequate processing of polymeric matrices filled with compounds that act as radar absorbing centers in the microwave range. This work shows the electromagnetic evaluation of RAM based on CoTi and La doped Ca hexaferrite. Vibrating Sample Magnetization analyses show that ion substitution promoted low values for the parameters of saturation magnetization (123.65 Am2/kg) and coercive field (0.07 T) indicating ferrite softening. RAM samples obtained using different hexaferrite concentrations (40-80 per cent, w/w) show variations in complex permeability and permittivity parameters and also in the performance of incidental radiation attenuation. Microwave attenuation values between 40 and 98 per cent were obtained. [Rezende, Mirabel Cerqueira] Institute of Aeronautics and Space, Brazil Nohara, Evandro Luís] Universidade de Taubaté, Brazil Silva, Valdirene Aparecida da] Institute of Aeronautics and Space, Brazil Pereira, José Jesus] Universidade de Taubaté, Brazil

The load assembly of RFX-mod consists of three toroidal conducting structures whose eddy currents affect the plasma equilibrium magnetic configuration. The high number of electromagnetic probes mounted on the components of the load assembly allowed to analyse the response of each structure to a variation of the magnetic field vertical component. The capability of evaluating the axisymmetric toroidal currents in the passive structures and therefore their contribution to the equilibrium configuration by a 2D FE MHD equilibrium code was validated. The design and implementation of a feedback control system of the magnetic field vertical component before the gas ionization allowed meeting the requirement of an accurate control of this quantity in view of operation at higher plasma current and independently of the magnetizing winding programming.

During the last year different saddle coil set-ups were tested on EXTRAP T2R performing experiments of plasma MHD modes active control. In particular, a series of shots both without and with plasma were aimed at the electromagnetic characterization of the open loop system and to the validation of a model developed for the design of a digital control system. A very good agreement was observed between model and experiment both in terms of single coil electromagnetic parameters and in terms of harmonic distribution at different frequencies. The quality of the harmonic content as a function of the number of active coils was also analysed. Finally, encouraging results were obtained comparing theoretical and experimental growth rates of unstable modes after applying static perturbations of different toroidal order n .

We investigated how the electrical contact of carbon foam with metallic surface can reduce its shielding properties. The bubble structure of the foam does not ensure a good electrical contact with the metal, and it leads to a significant reduction of the shielding effectiveness. A finite element numerical simulation was carried out by adopting a bubble/pore model of the internal microstructure of the foam, recovered by means of scanning electron microscope images. Experimental tests were carried out by inserting carbon foam samples into a coaxial transmission line. Numerical results agree well with experimental result showing significant performance reduction with respect to an ideal electrical contact.

The work presented in this report contributes to the development of Non Destructive Evaluation of the external post-tensioned ducts in bridges. A capacitive probe has been developed for bridge monitoring applications. The aim of this work is to improve its diagnostic.In a first step, a coaxial transmission line was developed to characterize the materials involved in the duct over the frequency range 50 MHz - 1 GHz. The cement grout, segregation products of the cement grout and the injection wax were studied.In the second part of this work the previous results are used in the modelling of the devices. A parametrical study has shown the ability to get from the signals an estimate of the thickness of the void in the duct. This estimation method has been validated using a laboratory duct. Further, several improvements of the probes are proposed to get signals containing more information in order to get a better estimation of the target parameters., Les travaux présentés dans cette thèse contribuent au développement du contrôle non destructif des conduits de précontrainte extérieure dans les ouvrages d'art. Une sonde capacitive a été développée pour ausculter ces conduits. L'objectif est d'en améliorer le diagnostic.Dans un premier temps, une cellule de mesure en transmission coaxiale a été développée pour caractériser les matériaux présents dans le conduit sur la bande de fréquence 50 MHz - 1 GHz. Le ciment, les produits de la ségrégation du ciment et la cire d'injection ont été étudiés.La deuxième partie du travail exploite ces résultats dans une modélisation directe du problème global. Une étude paramétrique nous a permis de proposer une méthode d'estimation de l'épaisseur de vide à l'intérieur du conduit à partir des signaux délivrés par la sonde, qui a pu être validée sur une maquette de conduit. A partir de ces résultats sont proposées plusieurs améliorations du dispositif visant à l'obtention de signaux plus riches issus des capteurs, afin de pouvoir estimer un plus grand nombre de paramètres.

Papier complet disponible sur : http://doi.editoracubo.com.br/10.4322/rbeb.2012.016; International audience; This paper presents the most commonly used method to characterize individual biological cells on a dielectric point of view. It is a force based technique which lays on dielectrophoresis and/or electrorotation. First the principle of these phenomena are described and analyzed with an extension to magnetic forces at the micrometric scale level. Secondly we present an experimental setup which permits to acquire the dielectrophoretic spectrum which is a dielectric signature of a cell. The main dielectric parameters can be deduced by fitting the theoretical response of the cell issued from a dielectric model and the experimental data. At the end we present an improved fitting method which takes advantage of a sensitivity analysis based on a probabilistic approach.

Combining the Molded Interconnect Device technology with the Laser Direct Structuring technology exhibits the potential of designing electrical and mechanical components on three-dimensional surfaces to increase functionality, level of integration and to reduce costs. When taking advantage of this technology especially in the design of RF devices, a precise knowledge of the electromagnetic parameters of the MID material is required, as the complex permeability and permittivity strongly influence the device performance. At present time, these materials are not electromagnetically characterized in the RF frequency range. In this paper different methods are therefore presented and compared with respect to their potentials for broadband electromagnetic characterization of Molded Interconnect Device materials.

The research of a supply strategy to reduce the torque ripple of a Switched Reluctance Machine (SRM) is the main aim of the study presented.The SRM is very attractive because of its simple structure. Unfortunately, its electromagnetic characteristics are highly nonlinear with regard to the angular position and the supply current (nonsinusoïdal structure, generally saturated state). Moreover, the different phases of the machine have to be successively commutated in order to maintain a continuous rotation. Therefore, the SRM polyphase torque is naturally pulsed, which can be unacceptable for certain applications.In order to reduce the SRM torque ripple with an appropriate control, its electromagnetic characteristics (torque and flux with regard to the position and the current) have to be very precisely determined. Several experimental methods of characterization are studied and compared herein.A model based on this experimental electromagnetic characterization is necessary for the synthesis of the control. The models found in the literature, compared with the experimental data, are not adapted to the SRM under study. An original model is then proposed.After defining an appropriate strategy for the phase commutation, different control algorithms for the minimization of the torque ripple are compared by simulation and experimentation. First, the limits of the classical linear control (Proportional Integral controller, etc) are determined. The performances of the PI controller are improved when the effects of the electromotrice forces are taken into account. Nevertheless, the torque ripple remains significant. In order to compensate the SRM nonlinearities, a nonlinear torque control has been simulated and tested on an experimental bench. Very promising results have been obtained at low and medium speeds., Le but général de l'étude présentée dans cet ouvrage est la recherche d'une stratégie d'alimentation permettant de réduire les ondulations de couple d'une Machine à Réluctance Variable à Double Saillance (MRVDS).La structure très simple de la MRVDS la rend très attractive. Malheureusement, ses caractéristiques électromagnétiques sont fortement non linéaires par rapport à la position angulaire et par rapport au courant d'alimentation (structure non sinusoïdale, fonctionnement généralement en régime saturé). De plus, pour assurer une rotation continue, il faut commuter successivement les différentes phases de la machine. Par conséquent, le couple polyphasé de la MRVDS est naturellement pulsé ce qui peut être intolérable pour certaines applications.Pour réduire par une commande appropriée les ondulations de couple de la MRVDS, ses caractéristiques électromagnétiques (couple et flux en fonction de la position et du courant) doivent être déterminées très précisément. C'est pourquoi, plusieurs méthodes de caractérisation expérimentales sont étudiées et comparées.Un modèle s'appuyant sur cette caractérisation électromagnétique expérimentale est ensuite nécessaire pour la synthèse de la commande. Les modèles de la littérature, confrontés aux données expérimentales, ne sont pas adaptés à la MRVDS étudiée. Ainsi une modélisation originale est proposée.Enfin, après avoir défini une stratégie appropriée pour la commutation des phases, différents algorithmes de commande destinés à minimiser les ondulations de couple sont comparés par simulation et par le biais d'expérimentations. Une première phase de cette étude consiste à déterminer les limites des commandes linéaires classiques (correcteur Proportionnel Intégral, etc). La prise en compte des effets dus aux forces électromotrices permet d'améliorer les performances du correcteur PI, mais les ondulations de couple restent importantes. Pour compenser les non linéarités de la MRVDS, une commande non linéaire en couple a été simulée et essayée sur un banc expérimental. Des résultats très prometteurs ont été obtenus pour des fonctionnements en basse et moyenne vitesses.

In this paper, a new measurement method is proposed to estimate simultaneously the complex permittivity and the complex permeability for a magneto-dielectric sample using a X-band rectangular waveguide WR90. The Sij-parameters at the reference planes in the rectangular waveguide loaded by a material sample are measured as a function of frequency using the E8634A Vector Network Analyzer. Also, by applying the two-dimensional finite difference in time domain (2D-FDTD), the expressions for these parameters as a function of complex permittivity and complex permeability are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity and complex permeability by matching the measured and calculated Sij-parameters. This method has been validated by estimating, at the X-band, the complex permittivity and complex permeability of two materials such as FR4 Epoxy and Titanium Carbide powder (TiC).