CNRS Institute of Electronics and Telecommunications, Rennes

Rennes, France

CNRS Institute of Electronics and Telecommunications, Rennes

Rennes, France
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Bernard L.,French German Research Institute of Saint Louis | Chertier G.,French German Research Institute of Saint Louis | Sauleau R.,CNRS Institute of Electronics and Telecommunications, Rennes
IEEE Antennas and Wireless Propagation Letters | Year: 2011

A reduced-size wideband single-feed circularly polarized patch antenna is introduced for telemetry applications in S-band around 2300 MHz. The proposed structure consists of a slot-loaded patch antenna printed over an optimized metamaterial-inspired reactive impedance substrate (RIS). We demonstrate, step by step, the main role of each antenna element by comparing numerically and experimentally the performance of various antenna configurations: antenna over a single- or dual-layer substrate, standard patch or slot-loaded patch, antenna with or without RIS. The final optimized structure exhibits an axial-ratio bandwidth of about 15% and an impedance bandwidth better than 11%, which is much wider than the conventional printed antenna on the same materials. © 2011 IEEE.


Chahat N.,CNRS Institute of Electronics and Telecommunications, Rennes | Zhadobov M.,CNRS Institute of Electronics and Telecommunications, Rennes | Sauleau R.,CNRS Institute of Electronics and Telecommunications, Rennes | Ito K.,Chiba University
IEEE Transactions on Antennas and Propagation | Year: 2011

A new compact planar ultrawideband (UWB) antenna designed for on-body communications is presented. The antenna is characterized in free space, on a homogeneous phantom modeling a human arm, and on a realistic high-resolution whole-body voxel model. In all configurations it demonstrates very satisfactory features for on-body propagation. The results are presented in terms of return loss, radiation pattern, efficiency, and E-field distribution. The antenna shows very good performance within the 3-11.2 GHz range, and therefore it might be used successfully for the 3.1-10.6 GHz IR-UWB systems. The simulation results for the return loss and radiation patterns are in good agreement with measurements. Finally, a time-domain analysis over the whole-body voxel model is performed for impulse radio applications, and transmission scenarios with several antennas placed on the body are analyzed and compared. © 2006 IEEE.


Muhammad S.A.,CNRS Institute of Electronics and Telecommunications, Rennes | Sauleau R.,CNRS Institute of Electronics and Telecommunications, Rennes | Legay H.,Thales Alenia
IEEE Transactions on Antennas and Propagation | Year: 2012

New configurations of small-size shielded metallic Fabry-Perot (FP) antennas with improved performance over a large frequency band are presented in -band for space missions. The bandwidth enlargement is obtained by stacking two FP cavities of different size, each of them presenting a low quality factor. Their radiating apertures measure around λ 0 and 2 × λ 0, respectively. Concentric corrugations are also introduced between both cavities to control the higher-order modes that are excited systematically in shielded small-size FP antennas due to lateral resonances. The obtained results are compared to those of a single-stage FP cavity antenna with the same aperture size. Several prototypes have been fabricated and measured. An aperture efficiency higher than 70%, a reflection coefficient smaller than -15 dB, and sidelobe levels lower than 20 dB have been obtained experimentally, over a wide frequency band (2.4-2.66 GHz). These characteristics make stacked FP cavity antennas very attractive to replace global coverage horn antennas, or to be used in feed clusters of multiple-beam antennas, especially in - and -bands, where they lead to more compact and less bulky solutions compared to classical feed horns. © 2011 IEEE.


Albani M.,University of Siena | Pavone S.C.,University of Siena | Casaletti M.,University Pierre and Marie Curie | Ettorre M.,CNRS Institute of Electronics and Telecommunications, Rennes
Optics Express | Year: 2014

The focusing capabilities of an inward cylindrical traveling wave aperture distribution and the non-diffractive behaviour of its radiated field are analyzed. The wave dynamics of the infinite aperture radiated field is clearly unveiled by means of closed form expressions, based on incomplete Hankel functions, and their ray interpretation. The non-diffractive behaviour is also confirmed for finite apertures up to a defined limited range. A radial waveguide made by metallic gratings over a ground plane and fed by a coaxial feed is used to validate numerically the analytical results. The proposed system and accurate analysis of nondiffractive Bessel beams launched by inward waves opens new opportunities for planar, low profile beam generators at microwaves, Terahertz and optics. © 2014 Optical Society of America.


Liu M.,CNRS Institute of Electronics and Telecommunications, Rennes | Crussiere M.,CNRS Institute of Electronics and Telecommunications, Rennes | Helard J.-F.,CNRS Institute of Electronics and Telecommunications, Rennes
IEEE Transactions on Broadcasting | Year: 2012

In contrast to the classical cyclic prefix (CP)-OFDM, the time domain synchronous (TDS)-OFDM employs a known pseudo noise (PN) sequence as guard interval (GI). Conventional channel estimation methods for TDS-OFDM are based on the exploitation of the PN sequence and consequently suffer from intersymbol interference (ISI). This paper proposes a novel data-aided channel estimation method which combines the channel estimates obtained from the PN sequence and, most importantly, additional channel estimates extracted from OFDM data symbols. Data-aided channel estimation is carried out using the rebuilt OFDM data symbols as virtual training sequences. In contrast to the classical turbo channel estimation, interleaving and decoding functions are not included in the feedback loop when rebuilding OFDM data symbols thereby reducing the complexity. Several improved techniques are proposed to refine the data-aided channel estimates, namely one-dimensional (1-D)/two-dimensional (2-D) moving average and Wiener filtering. Finally, the MMSE criteria are used to obtain the best combination results and an iterative process is proposed to progressively refine the estimation. Both MSE and BER simulations using specifications of the DTMB system are carried out to prove the effectiveness of the proposed algorithm even in very harsh channel conditions such as in the single frequency network (SFN) case. © 2012 IEEE.


Chahat N.,CNRS Institute of Electronics and Telecommunications, Rennes | Valerio G.,CNRS Institute of Electronics and Telecommunications, Rennes | Zhadobov M.,CNRS Institute of Electronics and Telecommunications, Rennes | Sauleau R.,CNRS Institute of Electronics and Telecommunications, Rennes
IEEE Transactions on Antennas and Propagation | Year: 2013

The on-body propagation at 60 GHz is studied analytically, numerically and experimentally using a skin-equivalent phantom. First, to provide analytical-based fundamental models of path gain, the theory of propagating waves near a flat phantom is studied by considering vertical and horizontal elementary dipoles. The analytical models are in excellent agreement with full-wave simulations. For a vertically polarized wave, a minimum power decay exponent of 3.5 is found. Then, propagation on the body is investigated experimentally in vertical and horizontal polarizations using two linearly-polarized open-ended waveguides. The analytical models fit very well with the measurements. Furthermore, the effect of polarization on the antenna performance is studied numerically and experimentally. © 1963-2012 IEEE.


Yang T.,CNRS Institute of Electronics and Telecommunications, Rennes | Ettorre M.,CNRS Institute of Electronics and Telecommunications, Rennes | Sauleau R.,CNRS Institute of Electronics and Telecommunications, Rennes
IEEE Microwave and Wireless Components Letters | Year: 2012

A novel phase shifter is proposed based on a substrate-integrated-waveguide (SIW) technology. It consists of several phase channels made by SIW resonators loaded with extra metallic posts. These metallic posts act as inductive posts controlling the resonant frequency of the SIW resonators. Circular slots on the upper plate of the SIW structure are used to selectively disconnect these inductive posts from the upper plate of the structure to tune the resonant frequency. It is shown that by properly controlling the resonant frequency in each channel, the phase gradient between adjacent channels exhibits a linear phase progression at the operating frequency. As a result, a novel phase shifter is obtained accordingly. Based on this approach, a phase shifter prototype made by five channels is proposed to validate the concept. Each channel consists of three SIW resonators which form a third-order bandpass filter for impedance matching. Experimental results demonstrate that the resulting phase shifter has more than 10% fractional bandwidth for a 15$ \circ phase gradient across adjacent channels with a phase error of $\pm 5 \circ. The insertion loss is less than 1.5 dB in the considered band. The experimental results agree well with full-wave simulations. The proposed phase shifter is expected to be easily implemented with active components. © 2001-2012 IEEE.


Legeay G.,CNRS Institute of Electronics and Telecommunications, Rennes | Castel X.,CNRS Institute of Electronics and Telecommunications, Rennes
Thin Solid Films | Year: 2012

Thin films of amorphous indium tin oxide were deposited by soft sputtering. The film was gradually annealed in air at temperatures from 110°C to 150°C. Its structural and electrical properties were monitored in order to get a better understanding of the annealing process. Firstly, carrier density decreases by oxygen intake. Crystallization speeds up at 150°C, with a 2.5 D growth of crystallites. The preferred orientations come from sputtering induced seeds. Then, the carrier density increases again due to tin activation. Meanwhile, the carrier mobility is more damaged by the low temperature annealing in air than by a standard annealing in a reducing atmosphere. Thus, tin oxide segregation is suspected at grain boundaries. © 2012 Elsevier B.V. All rights reserved.


Ettorre M.,University of Michigan | Ettorre M.,CNRS Institute of Electronics and Telecommunications, Rennes | Grbic A.,University of Michigan
IEEE Transactions on Antennas and Propagation | Year: 2012

The generation of Bessel beams using a leaky radial waveguide is presented. The radial waveguide consists of a capacitive sheet over a ground plane. It supports an azimuthally invariant leaky-wave mode whose normal electric-field component is a truncated, zeroth-order Bessel function. The annular spectrum and nondiffractive extent of the Bessel beam is clearly linked to the complex wavenumber of the leaky-wave mode. The fields inside the radial waveguide are derived using classical vector potential techniques. A vector approach is employed to avoid paraxial approximations of earlier works and the associated limitations on shaping the Bessel beam. Design rules are provided to synthesize a desired propagating Bessel beam. A simple coaxial feed is proposed for the radial waveguide and its input impedance is derived analytically. The analytical results are also validated numerically. The proposed structure and design procedure can be used for generating arbitrary zeroth-order propagating Bessel beams at microwave and millimeter-wave frequencies. © 1963-2012 IEEE.


Lemoine C.,CNRS Institute of Electronics and Telecommunications, Rennes | Amador E.,CNRS Institute of Electronics and Telecommunications, Rennes | Besnier P.,CNRS Institute of Electronics and Telecommunications, Rennes
IEEE Transactions on Antennas and Propagation | Year: 2011

Reverberation chambers were recently proposed to simulate Rician radio environment with controllable K-factor. The K-factor is also a parameter that may tell how ideal may be a reverberation chamber when it is used for other more conventional purposes. This paper is dedicated to the problem of the correct estimation of K in a reverberation chamber given a set of data measured along a stirring process. © 2010 IEEE.

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