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This article presents the design of a flat Luneburg metalens antenna at V-band using gap waveguide (GW) technology. The metalens consists of a parallel plate waveguide (PPW) loaded with metallic pins whose height is modulated to get an effective refractive index that follows the Luneburg equation. A Groove GW (GGW) H-plane horn is used to illuminate the metalens, such that the rays are collimated and a planar wavefront is generated in the direction of propagation. Since the structure at hand is planar, it can be efficiently integrated on flat surfaces. Moreover, the fully metallic structure is mechanically robust and presents lower losses than lenses including dielectric substrates. A prototype has been fabricated and tested, simulations and experimental results are in very good agreement. The metalens yields an input reflection coefficient (S11) below −10 dB from 45 to 70 GHz, whereas the −3 dB gain fractional bandwidth is 26.2% with respect to a center frequency of 60 GHz, with a peak of 22.5 dB at 61 GHz. These features make this design an interesting solution for millimeter-wave (MMW) applications. This work was supported in part by MCIN/AEI/ 10.13039/501100011033/FEDER “Una manera de hacer Europa” under Project RTI2018-094475-B-I00 and in part by the Spanish State Research Agency under Project PID2019-109984RBC43/AEI/10.13039/ 501100011033.

International audience; End-fire arrays are among the best candidate for high directivity and compact dimensions. Several solutions for the synthesis of superdirective arrays have been proposed in the literature. However, what is called a "superdirective" array suffers inevitably high losses and very poor radiation efficiency. More appealing is the joint optimization of directivity and efficiency, or the intrinsic gain, of the antennas. This paper set side by side the directivity and gain optimization methods based on the Spherical Wave Expansion (SWE) theory. The synthesis of superdirective and supergain end-fire arrays is proposed when Huygens sources, which attain the highest level of directivity, or simple bent dipoles are selected as elements of the array. On behalf of the spherical modal expansions, the results obtained for different optimizations of the two arrays are examined.

International audience; This work presents a full metal circularly-polarized lens-like antenna for Satcom applications at Ka-band. The antenna is composed of two continuous parallel plate waveguide (PPW) quasi-optical beamformers (QOBF), feeding an array of septum polarizers to generate circular polarization. The QOBFs operate over a wide band and provide a multi-beam coverage over a large field of view in the azimuthal plane, while maintaining a relatively simple mechanical design. The array of septum polarizers is based on a stepped profile to generate circular polarization with a good polarization purity in the uplink of Ka-band (27 - 31 GHz). The antenna is fully realized in aluminium. The antenna system provides 14 beams with alternating right/left handed circular polarization (RHCP/LHCP) with an axial ratio (AR) below 3 Db over an angular range of +/- 19 degrees in the uplink of Ka-Band. The maximum gain in the azimuthal plane at 30 GHz is about 21 dB over the whole angular range, with a scan loss lower than 1.5 dB. The antenna efficiency is better than 78% for all beams in the operative band.

International audience

Space Systems have been historically characterised by high performance, high reliability and high cost. Every new generation of space systems tends to improve performance, keep as much as possible reliability, speeding the lead time and lower the cost. Aggressive approach is nowadays followed by some of the players of the new space ecosystem where, for instance, reli- ability can be relaxed thanks for the in-orbit redundancy or robustness to failures by having a constellation with a high number of satellites. This push towards the technology and system limit requires to investigate new methods for the manufacturing of RF/Microwave parts. RF devices such as those based on waveguide structures, benefit from an additive manufacturing approach in terms of radio frequency (RF) performance and compactness. However each manufacturing approach comes with specific features and limitations which need to be well understood and, in some cases, even taking advantage of them. This paper provides a short review of some of the RF/Microwave parts already manufactured using this technology. The paper will focus mainly on metal 3D printing parts since this technology is, at the moment, well accepted by the space community. UPNA thanks the support of the Spanish Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación (MCIN/AEI/ 10.13039/501100011033) under Project PID2020-112545RB-C53.

International audience; The phaseless characterization of antennas enables to reduce the cost and to ease the measurement of radiating systems, especially at high frequencies. The complex near field is retrieved from the acquisition of the antenna radiated field magnitude only, thanks to appropriate phase retrieval algorithms. Thus, a two-scan approach combined to a Gerchberg-Saxton algorithm has proven to lead to accurate phase retrievals. However, instead of measuring the field on two spherical surfaces of different radii as conventionally performed, we propose to measure the magnitude of the field on a single sphere but for two antenna positions. This new strategy is easier to implement in a number of measurement setups. Numerical and experimental validations in a commercial, arch-based, measurement system are shown and discussed.

A conformal antenna with electronically tuning capability of its radiation pattern between broadside and monopole-like patterns is proposed. The antenna is based on a proximity-fed circular patch, loaded with a ring patch and four rectangular slots. The design is planar without any use of rigid shorting posts or a complex feeding network. The reconfigurability is achieved by activating and deactivating the slots using p-i-n diodes to switch between TM02 (monopole-like mode) and perturbed TM02 distributions (broadside mode) of the antenna. For conformability, the antenna is fabricated using a highly flexible PDMS-conductive fabric composite. All the antenna parts, including the RF switches, wires, and dc biasing circuit, are fully encapsulated by PDMS to provide resilience against deformation and harsh environment. Investigations on the RF performance and mechanical stability of the antenna were conducted. Under various bendings, it was demonstrated that all the antenna components, including those for electronic switching, remained intact and in working order even under the radius bending of 40 mm, thus maintaining good pattern reconfigurability and overall performance. When bent, the measured results at 5.2 GHz show a stable radiation performance relative to those of the flat case (i.e., the maximum gain of 2.9 dBi and the efficiency of 64% in the broadside mode, corresponding to 1.75 dBi and 52% in the monopole-like mode). To the best of our knowledge, all these features have never been demonstrated in previously published pattern reconfigurable antennas.

International audience; This paper presents two different design methodologies to cope with the somehow unexplored design of dual-band modulated metasurface (MTS) antennas with circular shape. In the first approach, one overlays two different modulations. Each modulation is appropriately chosen to provide a broadside beam for one of the bands and a very weak radiation for the other frequencies. The second approach builds on the active region modulated MTS concept, recently applied to broadband designs. In this case, the periodicity of the modulation at the central region of the aperture is selected to radiate at the high frequency band. In turn, a larger periodicity in the outer annular region provides the broadside beam at the low frequency band. Both approaches are compared and their advantages and drawbacks, discussed. © 2021 IEEE.

International audience; In this paper, a wearable waveguide surface for Body Area Network (BAN) communications is proposed. The designed structure is a via-less easy-to-manufacture waveguide surface optimized to work in the 2.6 GHz band. It is built on a flexible substrate, which makes it suitable for integration in clothes. The experimental measurement of the waveguide surface placed around the human torso is presented. This waveguide structure increases the transmission level between two half-wave dipole end-launches from -60 to -8 dB over a 435.8 mm distance.

This thesis deals with the characterization of antenna radiation patterns to improve the use of existing measurement systems. Two approaches are proposed in order to speed up the measurement of these radiation patterns, which is achieved by reducing the required number of field samples. The first one exploits the sparse spherical wave expansion of the field radiated by antennas. It only requires to know the maximum electrical dimension of the antenna. The second approach exploits the antenna external geometry and the measurement surface shape in order to build numerically an expansion basis tailored to the characterization problem. For both techniques, the minimal number of required field samples and an estimation of the field acquisition time at the IETR facilities are given, showing their potentialities to speed up the antenna measurements. Besides, an optimization strategy of the antenna positioning in post-processing is proposed. This procedure improves the quality of the reconstructed antenna radiation pattern from a given measurement. All the proposed methods have been validated using numerical and experimental datasets from various antenna types, different operating frequency bands and measured in several facilities, demonstrating thereby their versatility and generality.; Cette thèse traite de la caractérisation du diagramme de rayonnement des antennes afin d’améliorer l’utilisation des systèmes de mesure existants. Deux approches sont proposées en vue d'accélérer la mesure du diagramme de rayonnement des antennes en diminuant le nombre d'échantillons requis. La première exploite la décomposition parcimonieuse du champ rayonné par les antennes dans la base des ondes sphériques et nécessite seulement la connaissance de la dimension électrique maximale de l'antenne. La seconde approche utilise les dimensions externes de l'antenne et la surface de mesure afin de construire numériquement une base adaptée au problème de mesure d'antenne. Pour ces deux techniques, le nombre minimal d'échantillons du champ requis et une estimation du gain en temps de mesure à l'IETR sont donnés, montrant ainsi leur intérêt. En complément, une stratégie permettant d'optimiser le positionnement de l'antenne en post-traitement au sein de la base de mesure a été proposée afin d'améliorer la qualité du diagramme de rayonnement reconstruit. Toutes les procédures de mesure et traitements associés ont été validés sur des données numériques et expérimentales provenant d'antennes de types variés, opérant dans diverses bandes de fréquence et mesurées dans plusieurs chambres anéchoides, démontrant ainsi leur caractère général.

Automated systems based on wearable sensors for livestock monitoring are becoming increasingly popular. Specifically, wireless in-body sensors could yield relevant data, such as ruminal temperature. The collection of such data requires an accurate characterization of the in-to-out body wireless channel between the in-body sensor and the gateway. The aim of this study is to experimentally characterize the in-to-out-body propagation loss for cows and horses at 433, 868, and 1400 MHz. Measurements were conducted in vivo on five different fistulated cows and five horse cadavers using specialized robust in-body capsule antennas inside the animals' abdomen. Next, the in-body antenna gain was deembedded from the wireless channel, and the in-to-out body propagation loss was obtained as the difference between measured unobstructed line-of-sight path losses and in-to-out-body path losses. The measurements showed a body propagation loss of (mean +/- standard deviation) 30.8 +/- 4.1 dB, 44.5 +/- 4.8 dB, and 54.2 +/- 4.7 dB for cows at 433, 868, and 1400 MHz, respectively. For horses, the body propagation losses were 23.2 +/- 3.8 dB, 31.0 +/- 4.7 dB, and 44.4 +/- 3.2 dB at 433, 868, and 1400 MHz, respectively. These results are important to determine the wireless range of WBANs to optimize the network topology and estimate the associated network cost for large-scale monitoring systems.

International audience; The efficiency of an on-body wireless power transfer system for implant powering is defined by how the electromagnetic energy interacts with the lossy, heterogeneous, and dispersive body tissues. The objective of this study is to discuss the methodology and evaluate the theoretical bounds for the frequency-dependent electromagnetic energy transfer efficiency. We propose a simplified model that uses a finite tissue-equivalent phantom enclosing an implantable receiver surrounded by a medium that represents a transmitter matched to the wave impedance of the body. This model is used to study different cases and evaluate the wireless power transfer efficiency as a function of the operating frequency and implantation depth. The obtained results can be used as a guideline to choose the design parameters and constraints of the on-body power source and gauge its performance against the predicted maximum achievable efficiency.

International audience; A miniature frequency-tunable slot-loop antenna (0.12800.0770) based on ferroelectric K0.5Na0.5NbO3 (KNN) interdigitated varactors is investigated in Ku-band. KNN material has been selected among the ferroelectric oxide family because of its competitive properties for microwave device applications. Its high permittivity value (r 360 at 10 GHz) and its wide frequency tunability under an external static electric field Ebias make it a promising candidate for frequency-agile antennas and circuits at microwaves. The antenna prototype has been designed and elaborated on MgO substrate (r = 9.8 and tan 10-4 at 10 GHz). Fabrication details including laser microetching process of the ferroelectric film are also described. The center frequency of the slot-loop antenna can therefore be tuned monotonously from 15.22 to 15.97 GHz under Ebias = 88 kV/cm, leading to a frequency tunability rate equal to 4.6%. These results demonstrate for the first time the ability of the KNN material to be used for miniature tunable antennas, in comparison with BaxSr1-xTiO3, currently considered as the most relevant material for such applications.

Accommodating two independent electronically phased arrays on the same surface is a solution to get a bi-band structure with distant frequencies. In the scientific literature, the hurdles are clearly exposed. In this thesis, the goal is to imagine new topologies and to determine innovative solution with multilayer printed technology to accommodate on the same surface two antenna arrays operating at distant frequencies, at a ratio of 1 to 10.L- and X-bands are considered in this thesis. Quite important scanning capabilities are expected in the two bands (+/- 60°). Only in one plane for L-band and in the two main planes,E and H, for X-band. X-band array is composed of stacked square patches and L-band array of stacked dipoles. Scanning capabilities are quite limited and fall short of expectations after optimization of the two arrays. Mutual effects are studied between the two optimized arrays.X-band array performance is finally improved thanks to the innovative use of three dimensional WAIM in the E and H-planes. A proof-of-concept mock-up is realized and measured. Measured results are consistent with those simulated and permit to validate the improvements made by the addition of the WAIM.; L’implantation de deux antennes réseaux à balayage électronique, entrelacées sur une même surface, est une solution pour obtenir une structure fonctionnant dans deux bandes de fréquences distinctes et relativement éloignées. Les solutions issues de la littérature scientifique révèlent la complexité du sujet. Le travail de la thèse consiste à imaginer des topologies originales et identifier des solutions novatrices en technologie imprimée multicouches pour implanter sur une même surface deux réseaux d’antennes fonctionnant à des fréquences éloignées dans un rapport 1 à 10.Dans cette thèse, les deux bandes considérées sont les bandes L et X. Des capacités de dépointage relativement importantes (+/- 60°) sont souhaitées dans les deux bandes,seulement dans un plan en bande L et dans les deux plans principaux, E et H, en bande X.Le réseau bande X est constitué de patchs carrés empilés et le réseau bande L de dipôles empilés. Après optimisation des deux réseaux, ils présentent tous les deux des capacités de dépointage relativement limitées et inférieures à celles attendues. Les effets mutuels entre les deux réseaux sont étudiés. Finalement, l’utilisation originale de WAIM tridimensionnels permet d’améliorer les capacités de dépointage du réseau bande X dans les deux plans E et H. Une maquette d’antenne est réalisée puis mesurée. Les résultats mesurés sont cohérents avec ceux simulés et permettent de valider les améliorations apportées par l’ajout des WAIM.

International audience; The design of 3D Wide-angle impedance matching is presented in this paper. The design of an X-band array element, further illustrating the use of 3D WAIMs, is first detailed. This X-band element presents limited scanning performance which is improved thanks to the addition of WAIMs. The need of 3D WAIMs is justified through an analytical model. Finally, the antenna design is presented with the optimized 3D WAIM placed above the X-band element. The improvements in scanning performance are analysed, through the active reflection coefficient and radiation patterns. © 2021 EurAAP.

Conférence virtuelle; International audience; A new pattern reconfigurable 2×2 array antenna is proposed. The antenna has two modes of operation, Array Mode and Multiple-Input-Multiple-Output (MIMO) Mode. The single element antenna used is a pattern reconfigurable U-slot antenna with four pattern configurations. An average efficiency of 80%, a peak gain of 9.4 dB, and an overlapped −10 dB impedance bandwidth of 200 MHz around the resonant frequency 3.65 GHzare achieved. The size of the proposed antenna is 140×140×21 mm3 , which is suitable for small cell base-stations. For the MIMO Mode, the antenna has a maximum ECC of 0.06 between the four patterns and a minimum isolation of 12.9 dB between the four ports. For the array Mode, the antenna has a peak gain of 12.5 dB, and steering angles for 0 ◦ ≤ θ ≤ 30◦ in the planes at φ = 0◦ and φ = 90◦ Pattern reconfigurability is achieved using electrical switching. The used substrate is FR-4 with a dielectric constant of Epsilon_r = 4.4, and a loss tangent of tan δ = 0.02.

International audience; We present the experimental validation of the dual-mode, polarization-agile parallel-fed continuous transverse stub (CTS) antenna architecture introduced in Part I of this two-part paper. The Ka-band dual-mode CTS array described in Part I is characterized when it radiates in horizontal and vertical polarization. To this end, it is combined with two different quasi-optical beamformers operating in a quasi-transverse electromagnetic (quasi-TEM) and in a quasi-transverse electric (quasi-TE 1 ) mode, respectively. The scanning capabilities of both multibeam antenna systems are demonstrated. The CTS array and its feed network comprising corrugated parallel-plate waveguides (CPPWs) are fabricated by additive manufacturing. Measurements show that the dual-polarized CTS antenna works between 29 and 32 GHz in a field of view of about 45°, achieving a peak gain of 31.3 dBi and very low cross polarization. These promising results pave the way for the realization of dual-circularly polarized beam-scanning antennas with application to broadband and compact Ka-band ground terminals.

The thesis makes an in-depth study of one of the classical problems in RF circuit design,the problem of impedance matching. Matching problem addresses the issue of transmitting the maximum available power from a source to a load within a frequency band. Antennas are one of the classical devices in which impedance matching plays an important role. The design of a matching circuit for a given load primarily amounts to find a lossless scattering matrix which when chained to the load minimize the reflection of power in the total system.In this work, both the theoretical aspects of the broadband matching problem and thepractical applicability of the developed approaches are given due importance. Part I of the thesis covers two different yet closely related approaches to the matching problem. These are based on the classical approaches developed by Helton and Fano-Youla to study the broadband matching problems. The framework established in the first approach entails in finding the best H infinity approximation to an L infinity function, Փ via Nehari's theory. This amounts to reduce the problem to a generalized eigen value problem based on an operator defined on H2, the Hankel operator, HՓ. The realizability of a given gain is provided by the constraint, operator norm of HՓ less than or equal to one. The second approach formulates the matching problem as a convex optimisation problem where in further flexibility is provided to the gain profiles compared to the previous approach. It is based on two rich theories, namely Fano-Youla matching theory and analytic interpolation. The realizabilty of a given gain is based on the Fano-Youla de-embedding conditions which reduces to the positivity of a classical matrix in analytic interpolation theory, the Pick matrix. The concavity of the concerned Pick matrix allows finding the solution to the problem by means of implementing a non-linear semi-definite programming problem. Most importantly, we estimate sharp lower bounds to the matching criterion for finite degree matching circuits and furnish circuits attaining those bounds.Part II of the thesis aims at realizing the matching circuits as ladder networks consisting of inductors and capacitors and discusses some important realizability constraints as well. Matching circuits are designed for several mismatched antennas, testing the robustness of the developed approach. The theory developed in the first part of the thesis provides an efficient way of comparing the matching criterion obtained to the theoretical limits.; La thèse étudie en profondeur l'un des problèmes classiques de la conception de circuits RF, le problème de l'adaptation d'impédance. L’adaptation d’impédance consiste à maximiser le transfert de puissance d'une source à une charge dans une bande de fréquences. Les antennes sont l'un des dispositifs classiques dans lesquels l'adaptation d'impédance joue un rôle important. La conception d'un circuit d'adaptation pour une charge donnée revient principalement à trouver une matrice de diffusion sans perte qui, lorsqu'elle est enchaînée à la charge, minimise la réflexion de la puissance dans l'ensemble du système.Dans ce travail, les aspects théoriques du problème de l'adaptation et l'applicabilité pratique des approches développées sont dûment pris en compte. La partie I de la thèse couvre deux approches différentes mais étroitement liées du problème de l'adaptation large bande. Le cadre développé dans la première approche consiste à trouver la meilleure approximation H infini d'une fonction L infini, Փ via la théorie de Nehari. Cela revient à réduire le problème à un problème généralisé de valeurs propres basé sur un opérateur défini sur H2, l'opérateur de Hankel, HՓ. La réalisabilité d'un gain donné est fournie par la contrainte, opérateur norme de HՓ inférieure ou égale à un. La seconde approche formule le problème de l'adaptation comme un problème d'optimisation convexe où une plus grande flexibilité est fournie aux profils de gain par rapport à l'approche précédente. Il est basé sur deux théories riches, à savoir la théorie de l'adaptation de Fano-Youla et l'interpolation analytique. La réalisabilité d'un gain donné est basée sur les conditions de dé-chaînage de Fano-Youla qui se réduisent à la positivité d'une matrice classique en théorie d'interpolation analytique, la matrice de Pick. La concavité de la matrice de Pick concernée permet de trouver la solution au problème au moyen de l'implémentation d'un problème de programmation semi-défini non linéaire. Ainsi, nous estimons des limites inférieures nettes au niveau d'adaptation pour les circuits d'adaptation de degré fini et fournissons des circuits atteignant ces limites.La partie II de la thèse vise à réaliser les circuits d'adaptation sous forme de réseaux en échelle constitués d'inductances et de condensateurs et aborde également certaines contraintes importantes de réalisabilité. Les circuits d'adaptation sont conçus pour plusieurs antennes non-adaptées, testant la robustesse de l'approche développée. La théorie développée dans la première partie de la thèse offre un moyen efficace de comparer le niveau d'adaptation atteint aux limites théoriques.

International audience; This letter introduces a technique for the power density (PD) pattern measurement in the near field taking into account the antenna/body coupling at millimeter waves (mmW). The proposed method employs a specifically designed structure reproducing the reflection coefficient from human skin. This structure is optimized to convert the absorbed PD into an infrared (IR) pattern, remotely recorded using a high-resolution IR camera for reconstruction of the PD distribution. As a validation example, numerical and experimental distributions are presented for a 4element patch antenna array and a conical horn antenna at 60 GHz. A very good agreement is demonstrated between simulations and measurements (correlation > 98%). The results suggest a strong potential of this technique for fast remote high-resolution PD measurements applied to characterization of wireless devices in vicinity of the human body.

International audience; Due to recent advancements and the success of versatile mobile applications, more and more services around the globe are being moved to the cloud. As a result, its limitations have become more evident. The major issues that cloud-based applications face include large latency, bottlenecks because of central processing, compromised security, and lack of offline processing. The drawbacks of cloud computing are reduced by fog and edge computing, where data are processed near the places where it is generated—at network edges or fog nodes—most importantly in a distributed way. Smart agriculture is an approach based on the Internet of Things (IoT) where cloud computing is not an option as the internet is usually not available at remote sites. In addition, pure edge computing also is not practical, as most sensor nodes are very small and they do not have enough computing power. Intermediate fog computing also is not a good choice, as fixed fog nodes (getaway nodes) do not work well with high node fluctuation caused by bad weather or harsh conditions. Considering these issues and limitations, we have proposed the idea of flying edge computing where an unmanned aerial vehicle (UAV) acts as an edge-computing machine. This can be an ideal solution for smart agriculture, given the size and remoteness of many agricultural areas. This technique can be called “wind or breeze computing” because the data are “blown” or moved by the current of computing. The Flying-Edge offers fast deployment of edge facilities in challenging locations and it can be a major step to accomplish the goal of IoT-based smart agriculture.

Smart and e-textiles have nowadays an important increasing place in the garment industry. The rise of embedded telecommunications, especially smartphones in our pocket, enables us to provide a power source and a wireless link for smart textiles. The main issue is to develop garments able to receive power from smartphones and communicate with them without flexibility and comfort constraints bound to embedded solid-state electronic components. Consequently, this article aims to develop a fully textile NFC combiner to transfer data and power between a smartphone and sensors without any electronic components. It precisely describes textile NFC multiple combiners composed of textile NFC antennas linked by two-wire transmission lines. Also, theoretical analysis, simulations, and experiments have been conducted to adapt the resonant frequency of such structures to the NFC technology (13.56 MHz). Finally, our article generalizes textile NFC combiner resonant frequency equations for multiple combiners with any number of antennas.

International audience; In this paper, a slot-based electronically steerable parasitic array radiator (ESPAR) antenna suitable for Internet of-Things (IoT) applications is proposed. The antenna can provide 12 directive and 2 slightly different omnidirectional radiation states. The 12 directive patterns allow the antenna to focus the radiated energy towards 6 different directions uniformly distributed in the azimuth plane and with 2 different beamwidths. The reconfiguration of the radiation pattern is based on the use of low-capacitance low-power consuming diodes that can be digitally controlled. The paper details the design of the antenna structure and the practical implementation of the reconfiguration mechanism, discussing the effects of real electronic components on the antenna performance. The antenna effectiveness is numerically and experimentally assessed.

In this thesis, we present Discontinuous Galerkin (DG) solvers made for solving multiple electromagnetism problems in 3D and in parallel on architectures containing many GPUs and CPUs thanks to the OpenCL library. This is done by introducing splitting methods and local time stepping, using a coloring on the graph describing the elements of the mesh considered.We then handle problems involving thin electric wires or antennas, for which DG methods lead to the apparition of oscillations in the neighborhood of these structures. The method that is presented proposes a coupling between Maxwell equations which describe the behaviour of electromagnetic waves and the telegrapher's equations which handle the evolution of the current in the wire.; Nous présentons dans cette thèse des solveurs de type Galerkin Discontinu (GD) permettant de résoudre divers problèmes d'électromagnétisme en 3D et en parallèle sur des architectures contenant un grand nombre de GPU et de CPU grâce à la bibliothèque OpenCL. Nous introduisons pour cela des méthodes de splitting d'équations et de pas de temps local utilisant un coloriage du graphe décrivant les éléments du maillage 3D.Nous nous intéressons ensuite plus particulièrement aux problèmes contenant des fils électriques minces ou des antennes, pour lesquels les méthodes de type GD entraînent la formation d'oscillations à proximité de ces structures. La méthode présentée propose un couplage entre les équations de Maxwell régissant le comportement des ondes électromagnétiques et les équations des télégraphistes qui décrivent l'évolution du courant dans un fil.

In this thesis, we present Discontinuous Galerkin (DG) solvers made for solving multiple electromagnetism problems in 3D and in parallel on architectures containing many GPUs and CPUs thanks to the OpenCL library. This is done by introducing splitting methods and local time stepping, using a coloring on the graph describing the elements of the mesh considered. We then handle problems involving thin electric wires or antennas, for which DG methods lead to the apparition of oscillations in the neighborhood of these structures. The method that is presented proposes a coupling between Maxwell equations which describe the behaviour of electromagnetic waves and the telegrapher's equations which handle the evolution of the current in the wire.; Nous présentons dans cette thèse des solveurs de type Galerkin Discontinu (GD) permettant de résoudre divers problèmes d'électromagnétisme en 3D et en parallèle sur des architectures contenant un grand nombre de GPU et de CPU grâce à la bibliothèque OpenCL. Nous introduisons pour cela des méthodes de splitting d'équations et de pas de temps local utilisant un coloriage du graphe décrivant les éléments du maillage 3D. Nous nous intéressons ensuite plus particulièrement aux problèmes contenant des fils électriques minces ou des antennes, pour lesquels les méthodes de type GD entraînent la formation d'oscillations à proximité de ces structures. La méthode présentée propose un couplage entre les équations de Maxwell régissant le comportement des ondes électromagnétiques et les équations des télégraphistes qui décrivent l'évolution du courant dans un fil.

This manuscript describes the design of communicating gas sensors using a sensitive layer produced from a layer of molybdenum halide ions ([Mo6X14] 2- with X = Cl, Br or I) which reacts chemically with oxygenated molecules, was the subject of a preliminary study in analytical mass spectrometry. The surface functionalization of the sensor is first achieved through the use of an electrospray source (ESI) that nebulization in charged droplets is sent under atmospheric pressure, to a target located under the spray. The variation of the dielectric characteristics of the layer is associated to a specific interaction of the sensitive layer with a gaseous compound. The millimeter wave signal transduction was developped through the analysis of the scattering parameters Sij of the device and/or its radiation pattern. The first detection sensitivity and selectivity tests were carried out based on the detection of gaseous molecules such as methanol and acetonitrile. In order to improve the performance of the communicating sensor, a high purity ion deposition method has been initiated through the use of the ion soft landing technique. In this context, the instrumental modifications that were necessary for the deposition of the selected ions under vacuum and according to their m/z ratio, were preceded by modeling studies of their behavior and their trajectory into the mass spectrometer.; Ce manuscrit décrit la conception de capteurs de gaz communicants utilisant une couche sensible élaborée à partir d’un dépôt d’ions d’halogénures de molybdène ([Mo6X14] 2- avec X = Cl, Br ou I) dont la réactivité chimique vis-à-vis de molécules oxygénées, a fait l’objet d’une étude préliminaire en spectrométrie de masse analytique. La fonctionnalisation de surface du capteur est d’abord réalisée grâce à l’utilisation d’une source electrospray (ESI) dont la nébulisation en gouttelettes chargées est dirigée à pression atmosphérique, vers un support positionné sous le spray. La variation des caractéristiques diélectriques du matériau de surface a pu être associée à une interaction spécifique de la couche sensible avec un composé gazeux. La transduction du signal électromagnétique dans le domaine millimétrique a été développée au travers de l’analyse des paramètres de répartition Sij du dispositif et/ou de son diagramme de rayonnement. Des premiers tests de sensibilité et de sélectivité à la détection ont été réalisés à partir de de molécules gazeuses comme le méthanol et l’acétonitrile. Dans le but d’améliorer les performances des capteurs communicants, une méthode de dépôt d’ions de haute pureté a été initiée au travers de l’utilisation de la technique d’ion soft landing. Dans ce contexte, les modifications instrumentales qui ont été nécessaires au dépôt d’ions sélectionnés sous vide et selon leur rapport m/z, ont été précédées d’études de modélisation de leur comportement et de leur trajectoire dans le spectromètre de masse.

International audience; The characterization of the antenna radiation pattern in 3D has a well established theory. The increasing complexity of radiating structures under test leads to significant field acquisition duration. Using the Vector Spherical Harmonics expansion of the field and harnessing the sparsity of the antenna spectrum, one is able to decrease the required number of field samples. Also, an electric field radiated by a structure can be described with a few harmonics, and this fact can be harnessed to reduce the problem to an underdetermined linear system. This approach implies the resolution of a sparse recovery problem that requires the proper tuning of key parameters in order to ensure qualitative pattern reconstructions. In particular, the required number of field samples and the field acquisition time savings are addressed. Additionnal means to further improve the field reconstruction are proposed: the automatic determination of the error tolerance parameter and the best antenna orientation. All proposed procedures are assessed and validated on far field measurements data. © 2020 AMTA.

openaire: EC/H2020/736937/EU//M-CUBE Radio-frequency (rf) coils are used in all clinical and research magnetic-resonance-imaging (MRI) systems to excite nuclear spins and to receive signals from them. The quality of imaging depends strongly on the signal-to-noise ratio (SNR) and the transmit efficiency of the coils. The birdcage volume coils used in most MRI scanners for homogeneous imaging of a sample are typically shielded from the external systems of the MRI scanner, i.e., the gradient coils, to confine the rf field within the region of interest. However, the near magnetic field of a conventional copper rf shield surrounding a birdcage coil interferes destructively with the primary field of the coil in the sample, which significantly limits the SNR and the transmit efficiency. In the work presented here, we theoretically study and experimentally demonstrate the possibility of creating an artificial magnetic rf shield for a birdcage coil with constructive interference in a sample. This effect is similar to the in-phase reflection of antenna far fields from a magnetic shield but affects the near field in MRI. We build an analytical model of a birdcage coil shielded with a cylindrical impedance boundary and analyze the conditions for increasing the efficiency of the coil by means of the shield. We conclude that by replacing a copper shield with an artificial magnetic one, it is possible to reduce the dissipative intrinsic losses of the coil and increase the power absorbed by the sample, which improves the efficiency. To demonstrate the effect, we perform a detailed numerical simulation and an experiment with a small birdcage in a 7-T F-19 MRI system with a magnetic shield implemented as a periodic cylindrical metal structure with corrugations filled with a ceramic.

International audience; Enzymatic reactions involving glucose hold the potential for building implantable biosensors and embedded power generators for various medical applications. While Biofuel cells (BFCs) such as enzymatic glucose/O2 are ensured to benefit from abundant chemical resources that can be harvested in the immediate environment of the human body, the highly critical in vivo kinetics of biofuel cell is not yet fully understood. Unfortunately, existing solutions for real-time monitoring of the reaction on rodents are not possible today, or too bulky, which has a biasing impact on the animal behavior. This work presents a light, battery-less, and wireless strategy to continuously monitor a BFC implanted in a laboratory rat using a Frequency Identification (RFID) link. An extremely lightweight and flexible tag antenna of footprint lower than 10 cm² is presented with communication capability above 60 cm in field environment. The operational capabilities are demonstrated with a 24-hour continuous monitoring of an enzymatic glucose/O2 reaction, both in vitro and in vivo.

This paper presents a III/V compound silicon (Si) and gallium arsenide (GaAs) metasurface antenna to achieve beam-forming at 94 GHz. The metasurface antenna consists of a flat-panel system architecture and works in a holographic manner. The guided mode launched into the Si layer is converted to a planar wave-front using a quasi-optical pillbox feeding architecture, significantly simplifying the design process of the metasurface antenna. It is demonstrated that the developed metasurface can switch its radiation pattern in the azimuth plane by selectively activating between multiple input ports while beam forming in the elevation plane can be achieved by actively tuning the metamaterial elements forming the metasurface aperture. The simulated reflection coefficient patterns suggest an impedance matching better than -15dB at all input ports is achieved at 94 GHz. The radiation patterns of the antenna clearly demonstrate the 3D beam scanning capability of the presented metasurface antenna $(\theta =0^{\circ }/15^{\circ },\varphi =0^{\circ }/\pm 90^{\circ })$ at millimeter-wave frequencies.

International audience; A preliminary study of the design of an electrically small plasma-based resonator using a localized surface plasmon resonance (LSPR) above 1 GHz is presented. Such a resonator is intended to be used to develop an electrically small antenna with frequency agility. This resonator consists of a plasma discharge confined in a hemispherical glass shell 3 cm in diameter on a ground plane. From 1 to 1.5 GHz, the plasma electron density required to achieve the LSPR must be between 0.5 × 1011 and 1.4×1011 cm−3. Plasma losses are taken into account in this study and provide information on the required gas pressure. Typically for neon gas, the working pressure must be around 50 mTorr. A practical implementation using a miniature inductively coupled plasma (mICP) source is finally discussed.

International audience; In this paper, a patch antenna is designed forspatial modulation and ambient backscattering application at3.5GHz. Its goal is to pave the way for numerical com-munications towards 5G and IoT (Internet of Things). Forthose it is essential to design new antennas, that are compact,energy saving and radiation efficient. The Characteristic ModesAnalysis (CMA) is an interesting method for understanding anantenna properties, and so being able to design antennas ascompact as possible and keeping a good efficiency.

International audience; This paper deals with the experimental characterization of the on-body propagation channel for applications in wireless body area networks (WBAN)s. The on-body propagation was studied between two quarter-wavelength monopole antennas in the 900 MHz band and between two horn antennas in the 55-65 GHz range. Different locations all over the body, including arm, leg, front and back of the torso were studied for two human male subjects. The channel parameters in terms of path gain and delay spread were extracted from measurements for vertical and horizontal polarizations of the antennas in both frequency bands. Additionally, a wrist to arm path was studied in the 60 GHz band where the transmitter was rotated in 360and#x00B0; around the arm at a fixed distance from the receiver. We obtained a path gain exponent between 2 and 3 in the 900 MHz band and in the 2.4 to 6 range for the 60 GHz band. Higher path gains for vertical and horizontal polarizations were obtained in the 900 MHz and 60 GHz bands, respectively. Maximum mean excess delay and root mean square delay spread were 6.3 ns and and#x003C;2 ns in the 900 MHz band, respectively, while these values decreased by factors 3 and 10 in the 60 GHz band. IEEE

International audience; In this paper, matching networks of finite degree are computed. Additionally the presented results are compared with the lower fundamental bounds available in the literature. These bounds are used to certify the optimality of the provided matching networks in function of the attained matching tolerance. To illustrate the presented results, two different examples of matching problems are presented.

In the age of artificial intelligence, Big Data and the Internet of Things, the development of NoCs has become a priority. As part of the BBC project, we have opted for WiNoC interconnects, which provide efficient communication requirements at the intra-chip level (low latency, high throughput, minimal energy efficiency, compatibility with CMOS technology, adaptability for broadcast).This thesis focuses on the electromagnetic study the physical layer of WiNoC, and particularly on the characterization of propagation channels on silicon substrates.In this context, we highlight, through simulations and measurements in Ka and V bands, the problems of propagation in Si structures at very high frequency (cavities, surface waves and multiple paths).Subsequently, we propose a solution to limit these problems (due to reflections on the Si / Air interfaces) by adding an absorbing layer around the substrate. Using simulations and measurements in Q and V bands, we show improved transmission with a large bandwidth (>16 GHz).In order to reduce the size of the antennas and to increase the data rate, we study in the Sub-THz band, networks of monopoles embedded in a Si substrate placed between two metal plates.Finally, we estimate the performance and we show the possibility of transmitting at least 12 Gbps over a range of 21.2 mm and with an energy efficiency of the order of 4.5 pJ / bit. These results are comparable with competing solutions (WiNoC, RF interconnects, optical interconnects).; À l'ère de l'intelligence artificielle, de Big Data et de l'Internet des Objets, le développement des NoC est devenu une priorité. Dans le cadre du projet BBC, nous avons opté pour les interconnexions WiNoC, qui assurent les besoins de communications efficaces au niveau intra-puce (latence faible, débit élevé, efficacité énergétique minimale, compatibilité avec la technologie CMOS, adaptabilité pour le broadcast).Cette thèse se concentre sur l’étude électromagnétique la couche physique de WiNoC, et particulièrement sur la caractérisation des canaux de propagation sur des substrats silicium. Dans ce contexte, nous mettons en évidence au travers de simulations et de mesures en bandes Ka et V, les problèmes de la propagation à très hautes fréquences dans des structures sur Si (cavités, ondes de surface et trajets multiples). Par la suite, nous proposons une solution permettant de limiter ces problèmes dus aux réflexions sur les interfaces Si/Air en ajoutant une couche absorbante autour du substrat. Nous montrons à l’aide de simulations et de mesures en bandes Q et V, l’amélioration de la transmission et l’élargissement des bandes passantes. Dans le but de réduire la taille des antennes et d'augmenter le débit, nous étudions dans la bande Sub-THz des réseaux de monopoles intégrés dans un substrat Si placé entre deux plaques métalliques.Finalement, nous estimons les performances et nous montrons la possibilité de transmettre au moins 12 Gbps sur une portée de 21,2 mm et avec une efficacité énergétique de l’ordre de 4,5 pJ/bit. Ces résultats sont comparables avec les solutions concurrentes (WiNoC, RF guidées, optiques).

In the age of artificial intelligence, Big Data and the Internet of Things, the development of NoCs has become a priority. As part of the BBC project, we have opted for WiNoC interconnects, which provide efficient communication requirements at the intra-chip level (low latency, high throughput, minimal energy efficiency, compatibility with CMOS technology, adaptability for broadcast).This thesis focuses on the electromagnetic study the physical layer of WiNoC, and particularly on the characterization of propagation channels on silicon substrates.In this context, we highlight, through simulations and measurements in Ka and V bands, the problems of propagation in Si structures at very high frequency (cavities, surface waves and multiple paths).Subsequently, we propose a solution to limit these problems (due to reflections on the Si / Air interfaces) by adding an absorbing layer around the substrate. Using simulations and measurements in Q and V bands, we show improved transmission with a large bandwidth (>16 GHz).In order to reduce the size of the antennas and to increase the data rate, we study in the Sub-THz band, networks of monopoles embedded in a Si substrate placed between two metal plates.Finally, we estimate the performance and we show the possibility of transmitting at least 12 Gbps over a range of 21.2 mm and with an energy efficiency of the order of 4.5 pJ / bit. These results are comparable with competing solutions (WiNoC, RF interconnects, optical interconnects).; À l'ère de l'intelligence artificielle, de Big Data et de l'Internet des Objets, le développement des NoC est devenu une priorité. Dans le cadre du projet BBC, nous avons opté pour les interconnexions WiNoC, qui assurent les besoins de communications efficaces au niveau intra-puce (latence faible, débit élevé, efficacité énergétique minimale, compatibilité avec la technologie CMOS, adaptabilité pour le broadcast).Cette thèse se concentre sur l’étude électromagnétique la couche physique de WiNoC, et particulièrement sur la caractérisation des canaux de propagation sur des substrats silicium. Dans ce contexte, nous mettons en évidence au travers de simulations et de mesures en bandes Ka et V, les problèmes de la propagation à très hautes fréquences dans des structures sur Si (cavités, ondes de surface et trajets multiples). Par la suite, nous proposons une solution permettant de limiter ces problèmes dus aux réflexions sur les interfaces Si/Air en ajoutant une couche absorbante autour du substrat. Nous montrons à l’aide de simulations et de mesures en bandes Q et V, l’amélioration de la transmission et l’élargissement des bandes passantes. Dans le but de réduire la taille des antennes et d'augmenter le débit, nous étudions dans la bande Sub-THz des réseaux de monopoles intégrés dans un substrat Si placé entre deux plaques métalliques.Finalement, nous estimons les performances et nous montrons la possibilité de transmettre au moins 12 Gbps sur une portée de 21,2 mm et avec une efficacité énergétique de l’ordre de 4,5 pJ/bit. Ces résultats sont comparables avec les solutions concurrentes (WiNoC, RF guidées, optiques).

Small satellites (smallsats) provide low-cost access to space and have historically been used for flight technology demonstrations and limited-function space science activities. Novel antenna technologies have enabled high-performance smallsat telecommunications, science in Earth orbit, and the first CubeSat mission to deep space. In the past five years, technologists at NASA's Jet Propulsion Laboratory (JPL) have designed, tested, and successfully flown these innovative and enabling smallsat antennas. This article describes these innovations and their impact on smallsat performance for recent and future NASA missions.

International audience; Miniature wireless implantable bioelectronics provide powerful capabilities for biotelemetry, therapeutics, and neural interfacing. These technologies rely on antennas to communicate with external receivers, yet existing systems suffer from poor radiation performance. We address this issue by studying the through-tissue propagation, deriving the optimal frequency range, and obtaining the maximum achievable far-field radiation efficiency. Three problem formulations are considered with increasing complexity and anatomical realism. Polarization effects of TM and TE modes are investigated using an infinitesimal magnetic dipole and a magnetic current sources, respectively. The optimal operating frequency is found within the [108, 3 × 109]-Hz range and can be roughly approximated as f ≈ 2.2 × 107/d for deep implantation (i.e. d ≥ 2 cm). Considering the implantation depth, the operating frequency, the polarization, and the directivity, we show that about an order-of-magnitude efficiency improvement is achievable compared to existing devices. © 2019 European Microwave Association (EuMA).

We demonstrate a 3D printed holographic metasurface antenna for beam-focusing applications at 10 GHz within the X-band frequency regime. The metasurface antenna is printed using a dual-material 3D printer leveraging a biodegradable conductive polymer material (Electrifi) to print the conductive parts and polylactic acid (PLA) to print the dielectric substrate. The entire metasurface antenna is 3D printed at once; no additional techniques, such as metal-plating and laser etching, are required. It is demonstrated that using the 3D printed conductive polymer metasurface, high-fidelity beam focusing can be achieved within the Fresnel region of the antenna. It is also shown that the material conductivity for 3D printing has a substantial effect on the radiation characteristics of the metasurface antenna.

International audience; This paper presents the results obtained from 60 GHz propagation measurement campaigns in indoor environments. These measurements are performed in the frequency domain and are based on the use of a vector network analyzer (VNA). The analysis of the results makes it possible to characterize the propagation channel. In first measurement campaign, we show the influence of different types of antennas on the path loss characteristics in a hallway, while in the second campaign results highlight the effect of the type of antenna of the access point (AP) and its position on the angular impulse response of the channel inside a meeting room. All of these results are intended to lead to rules for the deployment of wireless high-speed local and personal area networks (WLANs/WPANs). © 2019 IEEE.

International audience; Site-specific weed management is one of the potential ways to reduce the chemical amount required to control crop weeds. Sources of optimization were investigated with spray width from an individual nozzle or a boom section width and spray deposition patterns were applied to different spatial coverage rates of weeds. The objective was to quantify herbicide saving possibilities as well as potential under-application areas. Simulations were performed with a collection of virtual weed infestation maps and an actual infestation map derived from aerial images. Results issued from the computation were expressed in terms of three indicators: (1) the ratio between herbicide amount in the case of a site-specific application and the amount deposited in the case of an application on the full field surface area; (2) the proportion of weed coverage on which the application rate is higher than 85% of the rated dosage; (3) the proportion of the weed surface on which the deposited application rate is lower than 50% of the rated dosage. The interest in reducing the section width depends on weed spatial distribution and aggregation degree. Moreover, in the case of uniformly dispersed small patches and the use of narrow sections (1 to 4 nozzles) equipped with triangular spray pattern nozzles, attention should be put to the increase of under-dosing areas.

The problem of impedance matching in electronics and particularly in RF engineering consists on minimising the reflection of the power that is to be transmitted, by a generator, to a given load within a frequency band. The matching and filtering requirements in classical communication systems are usually satisfied by using a matching circuit followed by a filter. We propose here to design matching filters that integrate both, matching and filtering requirements, in a single device and thereby increase the overall efficiency and compactness of the system. In this work, the matching problem is formulated by introducing convex optimisation on the framework established by the matching theory of Fano and Youla. As a result, by means of modern non-linear semi-definite programming techniques, a convex problem, and therefore with guaranteed optimality, is achieved. Finally, to demonstrate the advantages provided by the developed theory beyond the synthesis of filters with frequency varying loads, we consider two practical applications which are recurrent in the design of communication devices. These applications are, on the one hand, the matching of an array of antennas with the objective of maximizing the radiation efficiency, and on the other hand the synthesis of multiplexers where each of the channel filters is matched to the rest of the device, including the filters corresponding to the other channels.; Le problème de l'adaptation d'impédance en ingénierie des hyper fréquences et en électronique en général consiste à minimiser la réflexion de la puissance qui doit être transmise, par un générateur, à une charge donnée dans une bande de fréquence. Les exigences d'adaptation et de filtrage dans les systèmes de communication classiques sont généralement satisfaites en utilisant un circuit d'adaptation suivi d'un filtre. Nous proposons ici de concevoir des filtres d'adaptation qui intègrent à la fois les exigences d'adaptation et de filtrage dans un seul appareil et augmentent ainsi l'efficacité globale et la compacité du système. Dans ce travail, le problème d'adaptation est formulé en introduisant un problème d'optimisation convexe dans le cadre établi par la théorie de d'adaptation de Fano et Youla. De ce contexte, au moyen de techniques modernes de programmation semi-définies non linéaires, un problème convexe, et donc avec une optimalité garantie, est obtenu. Enfin, pour démontrer les avantages fournis par la théorie développée au-delà de la synthèse de filtres avec des charges complexes variables en fréquence, nous examinons deux applications pratiques récurrentes dans la conception de ce type de dispositifs. Ces applications correspondent, d'une part, à l'adaptation d'un réseau d'antennes dans le but de maximiser l'efficacité du rayonnement, et, d'autre part, à la synthèse de multiplexeurs où chacun des filtres de canal est adapté au reste du dispositif, notamment les filtres correspondant aux autres canaux.

International audience; The absorption mechanisms of Poisson-distributed disordered Metal-Insulator-Metal structures are investigated theoretically and numerically. In particular, from the Poisson point process, Slivnyak-Mecke integrals are used to predict the number of isolated particles and majority clusters as a function of the particle density z. Then, the impact of these numbers on peak, mean, and bandwidth absorbance is calculated by full-wave electromagnetic analysis. It is shown that the peak absorbance reaches a maximum value of higher than 0.9 for a particle density of 0.6 cm-2 originating from main contributions of monomers and dimers whereas trimers represent less than 6% of the total number of particles. The conclusions of these studies are experimentally confirmed by means of free-space characterization.

International audience; In this paper we investigate a method to determine the best available bandwidth for small embedded antennas. The available bandwidth depend both on the size and the position within a device, but also on the ohmic losses in the structure. Here we show a non-convex optimization problem, utilizing stored energies, and phrased as a current optimization problem we can determine theavailable bandwidth in a given region for a range of surface resistances. We illustrate the method by comparing the results with embedded antennas in a small IoT terminal. We show that an optimized embedded come rather close to the bounds.

The problem of impedance matching in electronics and particularly in RF engineering consists on minimising the reflection of the power that is to be transmitted, by a generator, to a given load within a frequency band. The matching and filtering requirements in classical communication systems are usually satisfied by using a matching circuit followed by a filter. We propose here to design matching filters that integrate both, matching and filtering requirements, in a single device and thereby increase the overall efficiency and compactness of the system. In this work, the matching problem is formulated by introducing convex optimisation on the framework established by the matching theory of Fano and Youla. As a result, by means of modern non-linear semi-definite programming techniques, a convex problem, and therefore with guaranteed optimality, is achieved. Finally, to demonstrate the advantages provided by the developed theory beyond the synthesis of filters with frequency varying loads, we consider two practical applications which are recurrent in the design of communication devices. These applications are, on the one hand, the matching of an array of antennas with the objective of maximizing the radiation efficiency, and on the other hand the synthesis of multiplexers where each of the channel filters is matched to the rest of the device, including the filters corresponding to the other channels., Le problème de l'adaptation d'impédance en ingénierie des hyper fréquences et en électronique en général consiste à minimiser la réflexion de la puissance qui doit être transmise, par un générateur, à une charge donnée dans une bande de fréquence. Les exigences d'adaptation et de filtrage dans les systèmes de communication classiques sont généralement satisfaites en utilisant un circuit d'adaptation suivi d'un filtre. Nous proposons ici de concevoir des filtres d'adaptation qui intègrent à la fois les exigences d'adaptation et de filtrage dans un seul appareil et augmentent ainsi l'efficacité globale et la compacité du système. Dans ce travail, le problème d'adaptation est formulé en introduisant un problème d'optimisation convexe dans le cadre établi par la théorie de d'adaptation de Fano et Youla. De ce contexte, au moyen de techniques modernes de programmation semi-définies non linéaires, un problème convexe, et donc avec une optimalité garantie, est obtenu. Enfin, pour démontrer les avantages fournis par la théorie développée au-delà de la synthèse de filtres avec des charges complexes variables en fréquence, nous examinons deux applications pratiques récurrentes dans la conception de ce type de dispositifs. Ces applications correspondent, d'une part, à l'adaptation d'un réseau d'antennes dans le but de maximiser l'efficacité du rayonnement, et, d'autre part, à la synthèse de multiplexeurs où chacun des filtres de canal est adapté au reste du dispositif, notamment les filtres correspondant aux autres canaux.

This thesis presents the design of small form factor Ultra Wide Band antennas with progressive waves shape, which is dedicated to ultra-short pulses radiation in a frequency band ranging from 300MHz to 3GHz. The aim is to combine a wide band of radiated frequencies and good performance while limiting the size of antennas. The insertion of a dielectric material has been associated with the design of Ultra Wide Band antennas to reduce their dimensions. This has led to the synthesis and characterization of innovative dielectric materials based on geopolymers, whose mastering of the value of the permittivity is possible. An antenna prototype has been manufactured and measurements of the different radiation characteristics were made and compared to the simulation results to ensure its good functioning. This antenna has also been associated with radar applications for the detection of targets in different environments (air and soil). The impulse responses obtained for the different tested radar scenes have been compared with the results obtained with other known antennas.; Ce mémoire présente une méthodologie de conception d’antennes Ultra Large Bande volumiques à ondes progressives, d’encombrement réduit, dédiées au rayonnement d’impulsions ultra-courtes dans une bande de fréquence allant de 300 MHz à 3 GHz. L’objectif est de concilier une large bande de fréquences rayonnées et de bonnes performances de rayonnements transitoires (niveau élevé, signaux brefs) tout en limitant l’encombrement des antennes. L’insertion d’un matériau diélectrique a été associée au design des antennes ULB afin de réduire leurs dimensions. Ceci a conduit à la synthèse et à la caractérisation de matériaux diélectriques innovants à base de géopolymères, dont la maîtrise de la valeur de la permittivité est possible. Un prototype d’antenne a été réalisé, des mesures des différentes caractéristiques de rayonnement ont été effectuées et comparées aux résultats de simulation pour s’assurer du bon fonctionnement de celle-ci. Cette antenne a également été associée à des applications radar pour la détection de cibles se situant dans différents milieux (air et sol). Les réponses impulsionnelles obtenues pour les différentes scènes radar testées ont été comparées aux résultats mesurées avec d’autres antennes connues.

International audience; Current noise fluctuations have been investigated in terahertz (THz) quantum well photodetectors embedded in antenna-coupled photonic architectures and compared with standard substrate-coupled mesa detectors. The noise measurements give a value of the photoconductive gain that is in excellent agreement with that extracted from previous responsivity calibrations. Moreover, our results confirm that the noise equivalent power (NEP) of the antenna-coupled devices is of the order of 0.2 pW/Hz0.5. This low NEP value and the wide band frequency response (∼GHz) of the detectors are ideal figures for the development of heterodyne receivers that are, at present, a valuable technological solution to overcome the current limitation of THz sensors.

International audience; In the present work we describe recent developments in the realization of a novel device for monitoring continuously a patient after a cerebrovascular event. The proposed technology is microwave imaging (MWI) exploiting the difference in dielectric properties of ischemic and hemorrhagic areas with respect to the other tissues present in the head. The goal of our work is to realize a prototype device that can be complementary to other imaging techniques, as support for physicians in the choice and control of therapies.

International audience; The IEEE Standards Association Standards Board (IEEE-SASB) approved the IEEE Std 1720™ 'Recommended Practice for Near Field Antenna Measurements' in 2012 [1]. More than fourty dedicated people from industry, academia and other institutions contributed to the creation of this new document. The main motivation for a new standard dedicated to near-field measurements was to complement the existing IEEE Std 149-1979™ 'Test Procedures for Antennas' [2]. © 2018 IEEE.

International audience; For the first time, a mm-wave personal exposure meter (mm-PEM) for the 5th generation of mobile networks (5G) exposure assessment in indoor diffuse fields is presented. The design is based on simulations and onphantom calibration measurements in a mm-wave reverberation chamber (RC) at 60 GHz. The mm-PEM consists of an array of nine antennas on the body. Using the mm-PEM, the incident power density (IPD) is measured in the unloaded RC, for the antenna(s) on the phantom and RC loaded with phantom. The uncertainty of the mm-PEM is then determined in terms of its response, which is defined as the ratio of antenna aperture for the above measurement scenarios. Using nine antennas, the designed meter has a response of 1.043 (0.17 dB) at 60 GHz which is very close to 1 (0 dB), the desired ideal responsevalue. The mm-PEM measured an IPD of 96.6 W.m − 2 at 60 GHz in the RC, for an input power of 1 W. In addition, the average absorption cross section of the phantom is determined as 225 cm 2, which is an excellent agreement with its physical dimensions.

International audience; In this work, the impedance matching problem in communication systems is formulated as a convex optimization problem. Important properties of the problem including feasibility, existence and uniqueness of solution are discussed. A practical example of matching filter synthesis using this technique is presented.