Institute Delectronique Et Of Telecommunications Of Rennes

Rennes, France

Institute Delectronique Et Of Telecommunications Of Rennes

Rennes, France
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Mejean C.,Institute Delectronique Et Of Telecommunications Of Rennes | Pometcu L.,Institute Delectronique Et Of Telecommunications Of Rennes | Benzerga R.,Institute Delectronique Et Of Telecommunications Of Rennes | Sharaiha A.,Institute Delectronique Et Of Telecommunications Of Rennes | And 3 more authors.
Materials Science and Engineering B: Solid-State Materials for Advanced Technology | Year: 2017

This paper presents a new electromagnetic absorbing material developed from carbon fibers loaded epoxy foam for an application in anechoic chamber. The composite was developed in order to replace the currently used pyramidal absorbers made of carbon particles loaded polyurethane foam. Epoxy-composites filled with different weight percentages (from 0 wt.% to 4 wt.%) and length (1 and 3 mm) of carbon fibers were achieved. After an optimization of the dispersion of carbon fibers in composite materials, the dielectric properties of the composites were measured using a coaxial-probe in the frequency range 4–18 GHz. Results have shown that the complex permittivity of the composites increases with the amount of charge and also with the length of the carbon fibers. Absorption performance of a prototype prepared with a low concentration (0.5 wt.%) of carbon fibers was measured in an anechoic chamber: it shows a mean gain of 10 dB compared to a commercial absorber. © 2017 Elsevier B.V.


Nguyen N.T.,Institute Delectronique Et Of Telecommunications Of Rennes | Nguyen N.T.,University of Nice Sophia Antipolis | Boriskin A.V.,Institute Delectronique Et Of Telecommunications Of Rennes | Le Coq L.,University of Rennes 1 | Sauleau R.,University of Rennes 1
IEEE Transactions on Antennas and Propagation | Year: 2016

We demonstrate that an integrated lens antenna (ILA) with a double lens (DL) focusing system can provide simultaneously a high broadside directivity and a low scan loss over a wide angular range. The proposed DL ILA system consists of a hemispherical substrate lens and a planoconvex objective lens. A prototype of a high-gain DL ILA with lenses made of a low permittivity dielectric material is fabricated and characterized in the frequency range of 75-79 GHz. The realized scan loss in terms of gain within a ±30° field of view is <1.1 dB in both planes. The performance of the DL ILA is compared with that of two hemispherical ILAs designed to provide the best broadside directivity and the lowest scan loss, respectively. © 2016 IEEE.


Zhang P.,Institute Delectronique Et Of Telecommunications Of Rennes | Jaques E.,Institute Delectronique Et Of Telecommunications Of Rennes | Rogel R.,Institute Delectronique Et Of Telecommunications Of Rennes | Bonnaud O.,Institute Delectronique Et Of Telecommunications Of Rennes
ECS Transactions | Year: 2012

A novel polysilicon vertical thin film transistor (VTFT) has been fabricated based on a low-temperature (T≤600°C) process. This new structure eliminates the large overlapping area between source and drain, and thus reduced the off-current and increased the Ion/Ioff ratio. The technologically key point lies in the introduction of an insulating layer between source and drain, and the electrical properties of the fabricated VTFTs using different insulating layers are compared. These first results highlight that the SiO2 insulating layer shows great advantages over the Si3N4 insulating layer. The reduced off-current has revealed some potential applications for high density integration and high drive current. © The Electrochemical Society.


Zhang P.,Institute Delectronique Et Of Telecommunications Of Rennes | Jacques E.,Institute Delectronique Et Of Telecommunications Of Rennes | Rogel R.,Institute Delectronique Et Of Telecommunications Of Rennes | Coulon N.,Institute Delectronique Et Of Telecommunications Of Rennes | Bonnaud O.,Institute Delectronique Et Of Telecommunications Of Rennes
Solid-State Electronics | Year: 2013

A new concept of vertical thin film transistor (TFT), called thin film transistor comb (TFTC), is proposed based on polycrystalline silicon (polysilicon) deposited at low temperature (T ≤ 600 °C). This structure, compatible with glass substrates, is designed to have up to 4 teeth and enables to get a high channel width W with a short channel length L. The channels of TFTC are made of a non-intentionally doped (NID) polysilicon layer between two in situ heavily-doped polysilicon layers; all these three layers are deposited by low pressure chemical vapor deposition (LPCVD) method. Electrical characteristics of TFTC show relatively high on-currents (ION) correlated with the geometric parameters. However, high off-currents (I OFF) are also observed due to the large overlapping area between drain and source regions. © 2012 Elsevier Ltd. All rights reserved.


Bor J.,Institute Delectronique Et Of Telecommunications Of Rennes | Lafond O.,Institute Delectronique Et Of Telecommunications Of Rennes | Fuchs B.,Institute Delectronique Et Of Telecommunications Of Rennes | Merlet H.,Canon Inc. | And 2 more authors.
8th European Conference on Antennas and Propagation, EuCAP 2014 | Year: 2014

The control of dielectric constant is an important issue in the design of many microwave antenna systems such as gradient index lens antennas. An innovative technological process has been developed to easily manufacture dielectric based antenna systems and microwave components from the use of foam material. This process is cheap and easy to implement. It has been applied to design a flat Luneburg lens from one single foam material. The good agreement between simulations and measurements of the lens antenna between 57 and 65 GHz validate the proposed technology. © 2014 European Association on Antennas and Propagation.


Pichon L.,Institute Delectronique Et Of Telecommunications Of Rennes | Rogel R.,Institute Delectronique Et Of Telecommunications Of Rennes | Jacques E.,Institute Delectronique Et Of Telecommunications Of Rennes | Salaun A.C.,Institute Delectronique Et Of Telecommunications Of Rennes
Physica Status Solidi (C) Current Topics in Solid State Physics | Year: 2014

N-type in-situ doped SiNWs based resistors are fabricated and used as gas (ammonia) sensors. SiNWs are prepared by vapour-liquid-solid method (VLS) using gold as catalyst. In-situ doping level is adjusted by varying the phosphine to silane mole ratio. Because SiNWs can act as sensitive units specific design is developed to allow large sensing areas, following a process fabrication compatible with a mass production planar layout. SiNWs doping effect on ammonia detection is carried out under controlled ammonia/nitrogen mixture varying from 2 ppm to 700 ppm. Results highlight that the relative response, Sg=(I0-Ig)/I0, where I0 and Ig are the current values in vacuum and reactive ambient respectively, follows a linear behaviour. The relative sensitivity, (S=ΔSg/Δ[NH3]) decreases, whereas the sensitivity (SxI0) increases with the increase of the VLS SiNWs doping level. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


El-Makhour R.,EMC Laboratory | De-Daran F.,EMC Laboratory | Lafon F.,EMC Laboratory | Drissi M.,Institute Delectronique Et Of Telecommunications Of Rennes | Fourn E.,Institute Delectronique Et Of Telecommunications Of Rennes
2010 Asia-Pacific Symposium on Electromagnetic Compatibility, APEMC 2010 | Year: 2010

This paper presents a modelling technique that predicts the detuning of a RF (Radio Frequency) receiver ahead of its installation into a vehicle. In fact, since the vehicle is rarely available during the equipment's development phase, it becomes necessary to finalise the product even before it can be tested in its operational environment. The proposed model is based on a circuit approach which permits a fast evaluation of the resonant frequency shifting. The comparison with a 3D full wave simulation confirms the robustness of the proposed technique. © 2010 IEEE.


Toutin T.,Canada Center For Remote Sensing | Wang H.,Canada Center For Remote Sensing | Chomaz P.,National School of Geographic Sciences | Pettier E.,Institute Delectronique Et Of Telecommunications Of Rennes
International Geoscience and Remote Sensing Symposium (IGARSS) | Year: 2012

Ortho-rectification using digital terrain models is a key issue for full polarimetric complex synthetic aperture radar (SAR) data because resampling the complex data can corrupt the polarimetric phase, mainly in study sites with relief. This research thus compared two approaches for the ortho-rectification of the complex SAR data: the polarimetric processing is performed before (scientist approach) or after (user approach) the geometric processing. A quantitative evaluation between the two approaches as a function of different geometric and radiometric parameters was thus performed to quantify the impact of the ortho-rectification on the complex polarimetric SAR. Radarsat-2 fine-quad data acquired over a rolling relief study site were geometrically processed using a lidar digital surface model. The evaluation results showed than the terrain slopes and land covers can potentially corrupt the polarimetric complex SAR data during the ortho-rectification. Advices are finally provided to reduce these impacts to an acceptable level for the users and their applications. Preliminaries results of simulated compact polarimetric SAR data of the new Canadian Radar Constellation Mission will be presented at the Conference. © 2012 IEEE.


Chafii M.,Institute Delectronique Et Of Telecommunications Of Rennes | Palicot J.,Institute Delectronique Et Of Telecommunications Of Rennes | Gribonval R.,French Institute for Research in Computer Science and Automation | Bader F.,Institute Delectronique Et Of Telecommunications Of Rennes
IEEE Transactions on Communications | Year: 2016

This paper establishes a necessary condition that must be satisfied by the modulation waveforms of any generalized waveforms for multicarrier (GWMC) system with better peak-to-average power ratio (PAPR) than conventional orthogonal frequency division multiplexing (OFDM). GWMC systems include in particular all classical multicarrier modulation systems. As a consequence, we show that OFDM has the best PAPR performance over all GWMC systems that do not satisfy this necessary condition. We also identify an infinite family of GWMC systems with the same PAPR performance as OFDM. To illustrate our results, we present the simulations of the PAPR behavior for different GWMC systems, including some with better PAPR performance than OFDM. © 2016 IEEE.


Khalighi M.-A.,École Centrale Marseille | Helard J.-F.,Institute Delectronique Et Of Telecommunications Of Rennes | Sadough S.M.-S.,Shahid Beheshti University | Bourennane S.,École Centrale Marseille
AEU - International Journal of Electronics and Communications | Year: 2010

In order to propose practical solutions for future communication systems employing a combination of multiple-input multiple-output (MIMO) structures and orthogonal frequency division multiplexing (OFDM), we analyse and compare the performances obtained by orthogonal and non-orthogonal space-time coding schemes. A simple iterative detector based on soft parallel interference cancellation (Soft-PIC) is used in the receiver in order to cope with the interference terms when using non-orthogonal schemes. First, we propose a modification of the log-likelihood ratio (LLR) calculation part in the Soft-PIC detector that provides an improvement of the receiver performance compared to previous implementations of this detector. Then, the performances of different space-time schemes proposed for two, three or four antennas at the transmitter and two antennas at the receiver are compared. In the case of perfect channel estimation, a substantial gain is obtained by using the appropriate non-orthogonal schemes for moderate-to-high spectral efficiency MIMO systems, which justifies the increased complexity of the receiver. This conclusion is conditioned to the presence of sufficient frequency diversity that is the case in a practical system. We also study the case of imperfect channel estimation at the receiver and discuss the choice of the appropriate space-time scheme. The gain offered by the non-orthogonal schemes is confirmed in that case, specifically for high spectral efficiency systems. © 2009 Elsevier GmbH. All rights reserved.

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