La mesure de Matières En Suspension (MES) est cruciale autant pour comprendre les transferts sédimentaires que pour les études des écosystèmes marins. Elles sont classiquement mesurées ponctuellement par des prélèvements d’eau in situ, ou à partir des propriétés optiques de l’eau. Mais depuis plusieurs décennies, les appareils acoustiques, ont montré leur capacité à mesurer ces MES sur de plus grands volumes. Ces mesures, en particulier celles de la concentration, s’appuient sur les propriétés de rétrodiffusion des particules. Mais ces mesures demeurent peu représentatives dans la mesure où le contenu en MES dans la colonne d’eau varie à différentes échelles de temps et d’espace. Dans un premier temps, ces travaux de thèse visent à montrer à travers des mesures in situ réalisées dans l’estuaire de l’Aulne qu’il est possible d’étendre spatialement la mesure par inversion des données issues de sondeurs multifaisceaux (SMF). Un modèle de rétrodiffusion adapté à la suspension d’intérêt, constituée dans cette étude d’agrégats estuariens, est d’abord élaboré. Puis grâce à des observations issues d’un profileur multifréquences, la concentration massique en MES, distribuée par classes de tailles, a pu être déterminée par la résolution d’un problème inverse. Ces informations permettent de déterminer les rayons équivalents de la suspension, grâce auxquels les données issues du SMF, au préalable calibrées par une méthode innovante, peuvent être inversées de manière directe. Une étude des incertitudes attachées aux valeurs de concentrations estimées est par la suite proposée afin de qualifier la pertinence des résultats. Puis dans un second temps, les conditions nécessaires à l’établissement d’un protocole de mesure des MES par système multi-capteur sont identifiées. Ce dernier permet la caractérisation en continu des MES à différentes échelles de temps et d’espace, en exploitant la complémentarité des mesures issues des différents instruments. / Measuring Suspended Particulate Matter (SPM) is essential to better understand sediment transport and marine ecosystems. SPM is traditionnaly estimated through in situ water samples analysis, or based on the optical properties of water. Yet for several decades, acoustical devices have shown their capability to measure SPM on larger volumes. These measurements (especially in terms of SPM concentration) are based on the backscattering properties of the particles. However, these measurements remain limited, since the SPM content in the water column is subjected to variations on both spatial and temporal scales.As a first step, this work aims at showing that it is possible to increase the degree of spatialization of the SPM measurements by inverting MultiBeam EchoSounder (MBES) data, through in situ measurements acquired in the Aulne macrotidal estuary. A backscattering model was first designed to describe the backscattering properties of the suspension of interest, consisting in this study in estuarine agregates. Then, thanks to multifrequency observations, the SPM mass concentration sorted by size classes was retrieved through the the resolution of the inverse problem. This kind of information allows to determine the equivalent spherical radius of the the whole suspension, through which the MBES data, calibrated beforehand using an original method, can be directly inverted. Subsequently, a study of the uncertainties attached to the final concentration estimate is proposed in order to qualify the relevance of the results.In a second step, the necessary conditions for establishing a measurement protocol of the SPM are identified. The latter allows continuous characterization of SPM at different spatial and temporal scales, by exploiting the complementarity of the measures delivered by different instruments.

Dans le cadre de cette thèse, on s'intéresse dans un premier temps à des matrices d'alimentation de type passif connues qui permettent de produire des faisceaux orthogonaux, et notamment à la matrice de Butler. On s'aperçoit qu'il n'existe qu'une méthode itérative permettant de déterminer les paramètres S d'une matrice de Butler symétrique. C'est pourquoi, on cherche à déterminer de manière analytique la matrice [S] d'une matrice de Butler symétrique à N = 2^n entrées et N sorties. On établit des formules de récurrence issues de l'étude de ce type de matrices pour plusieurs tailles. Des formules analytiques en sont déduites qui sont valables quelle que soit la valeur de N. On poursuit l'étude des matrices d'alimentation de réseau d'antennes en s'intéressant à la source focale d'une antenne multifaisceaux devant réflecteur basée sur une géométrie originale constituée de coupleurs directionnels tridimensionnels entrelacés. Cette structure est simulée. Ses nombreux paramètres sont optimisés afin d'aboutir à une solution répondant au cahier des charges. Une maquette est réalisée et testée. Les résultats obtenus sont prometteurs. Au final, cette source possède l'avantage d'avoir un fort niveau de réutilisation de ses éléments rayonnants et donc de limiter l'encombrement du système global qui est souvent un point critique, dans les satellites notamment. Pour finir, on s'intéresse à une structure dont le but est d'avoir une station au sol capable de suivre une cible sans dépointage. La poursuite en azimut est assurée par une partie mécanique, de type joint tournant ; celle en élévation par un module électronique. Le système se doit d'être compact, fiable, et de limiter les pertes ainsi que les coûts. Des compromis sont donc à effectuer. La partie rayonnante est réalisée en guide, la partie alimentation en technologie planaire. Une solution est proposée afin de faire la transition entre ces deux technologies : le circuit de répartition est directement relié à l'excitation des éléments rayonnants en mettant ces deux parties sur une même feuille de substrat. Ainsi, moins de câbles et de connecteurs sont nécessaires, ce qui diminue l'encombrement et les coûts. / In this PhD thesis, some feed networks are studied. First, a N x N symmetric Butler matrix is considered. Analytical formulas allowing constructing its [S] matrix are found and demonstrated. Second, a multibeam antenna focal array based on 3-D directional couplers is considered. This device has a high level of re-use of its radiating elements. Therefore, its global size is reduced. Its conception is explained. Measurement results are exposed. Last, a mechanic / electronic device is studied. It is used for tracking. It is a complex device with several parts. The fact that the conception of each part depends on each other is highlighted. Compromises and choices need to be made.

Made available in DSpace on 2015-03-13T17:08:39Z (GMT). No. of bitstreams: 1 NarelleMA_DISSERT.pdf: 7040966 bytes, checksum: 66462f8e5d4ada5ffd979bea8a0e35a9 (MD5) Previous issue date: 2014-02-21 / This work presents the results of the first imaging of continental slope adjacent to Potiguar Basin, in the equatorial Brazilian margin (NE Brazil). Swath bathymetry provided a complete coverage of seafloor between the upper and middle slope (100-1,300 m). Fifteen submarine canyons were mapped. The shape of the slope reflects in distinct spatial distribution of the canyons. The western area displays convex profiles which implied a greater amount of incisions by canyons. Some of them have gradient walls higher than 35?. They were classified according to location and morphology. The canyons with heads indenting shelf edge, association with a incised valley and a large fluvial system, high sinuosities, V shape, terraces along margins, further erosive features such as landslide and gullies allow to deduce a sandy-gravelly sedimentation. These canyons are associated with deposition of submarine fan systems that have been considered permeable hydrocarbon reservoirs. The presence of gullies, furrows and dunes demonstrates the role of bottom currents in the shaping of the slope. The enlargement of canyons and the change in the course when they cross the border fault imply that tectonic has also influenced in the morphology of deep waters environments of Potiguar Basin. The current sedimentation of continental slope is considered mixed because the sediments are composed of siliciclastics and bioclasts. Predominant siliciclastics are calcite, dolomite, quartz, and clay minerals. The presence of stable minerals (zircon, tourmaline and rutile), and fragmented bioclasts implies the contributions of Rivers A?u and Apodi / Esta disserta??o apresenta os resultados do primeiro imageamento realizado no talude continental, em ?rea adjacente ? Bacia Potiguar, na margem equatorial brasileira (NE Brasil). Dados de batimetria multifeixe forneceram uma cobertura completa do fundo oce?nico entre o talude superior e o talude intermedi?rio (100-1300 m). Quinze canyons submarinos foram mapeados. A forma do talude reflete na distinta distribui??o espacial dos canyons. A parte oeste apresenta perfis convexos o que implicou numa maior quantidade de incis?es pelos canyons. Alguns deles possuem paredes com declividades maiores que 35?. Os canyons foram classificados de acordo com sua localiza??o e morfologia. Os canyons com cabeceiras entalhadas na plataforma, conex?o com sistemas fluviais, altas sinuosidades, formas em V , terra?os ao longo das margens e com fei??es erosivas como ravinas permitem deduzir uma sedimenta??o areno-cascalhosa. Estes canyons s?o associados ? deposi??o de sistemas de leques submarinos que t?m sido considerados reservat?rios de hidrocarbonetos. A presen?a de ravinas, ranhuras e dunas demonstram o papel das correntes de fundo na forma do talude. Os alargamentos dos canyons e a mudan?a na dire??o do curso onde cruzam a falha de borda da bacia implicam que a tect?nica tamb?m influencia na morfologia dos ambientes profundos da Bacia Potiguar. A sedimenta??o atual do talude continental ? considerada mista, pois os sedimentos possuem componentes silicicl?sticos e biocl?sticos. Dentre os silicicl?sticos destacam-se calcita, dolomita, quartzo e os argilominerais. A presen?a de alguns minerais pesados tais como zirc?o, turmalina e rutilo, bem como biocl?sticos fragmentados, indicam a maturidade dos sedimentos e a contribui??o dos Rios A?u e Apodi para os sedimentos da ?rea de estudo

Marine geological surveys in Asköfjärden in the southern Stockholm Archipelago hasrevealed step like features in the sediments on the Baltic sea floor. The aim of this project is toanalyse the steps and possible formation processes from the survey data. The data used aretaken from the acoustic instruments multibeam echosunder and Chirp sonar sediment profiler.The multibeam reveal the seafloor topography and can detect water column features. TheChirp sonar produce sub-bottom profiles showing the sediments down to some tens of metersunderneath the sea floor. The multibeam data show multiple crescent shaped steps as well aselliptically shaped “pockmarks”. Water column data show what could be interpreted as seepsfrom the sea floor under these features. The sub bottom profile show deformation and fluidsignatures under the steps. Gas signatures and what could be other fluids are present. Theinterpretation concludes that the formation could be from either gas or groundwater seeps. Nodefinitive conclusions can be made from the data available for the present study, andapetrophysical or geochemical study of the study area cold provide further understanding ofthe formation of the steps.

Les réseaux d’alimentation d’antennes multifaisceaux sont un sous-système particulièrement important dans la mesure où ils permettent de réutiliser une même ouverture rayonnante pour l’ensemble des faisceaux à produire. Ces solutions trouvent naturellement application dans le spatial, l’espace disponible pour aménager des antennes étant fortement contraint sur les satellites. Plusieurs solutions de réseaux d’alimentation sont disponibles dans la littérature, incluant des structures quasi-optique ou lentilles et des structures guidées. Nous avons approfondie cette deuxième catégorie en étudiant différentes solutions, incluant les matrices de Blass, de Butler, de Nolen, ainsi que des structures à lois de phase uniformes. En particulier, un mode de dimensionnement des matrices de Nolen, défini comme un cas particulier asymptotique d’un algorithme de dimensionnement de matrices de Blass, a été proposé et validé expérimentalement en bande S. La flexibilité du dimensionnement des matrices de Nolen proposé a été exploitée pour concevoir une matrice à distribution d’amplitude non-uniforme, afin de réduire le niveau des lobes secondaires. Enfin, le caractère dispersif d’une alimentation en série a été utilisé pour rendre le pointage angulaire du faisceau produit par une antenne réseau linéaire indépendant de la fréquence de fonctionnement et pourrait être étendu à des matrices de Blass et Nolen. Des structures à lois de phase uniformes et à distribution d’amplitudes uniforme et gaussienne ont été approfondies, afin de mettre en évidence notamment le niveau de pertes intrinsèques. La structure à distribution d’amplitude gaussienne a été modifiée pour l’adapter à des applications d’antennes réseaux circulaires. L’ensemble des informations regroupées dans ce mémoire permet d’identifier la topologie de réseau d’alimentation la mieux adaptée à une application donnée. Une combinaison de différents concepts peut s’avérer une bonne solution dans certains cas. / Beam forming networks for multiple beam antennas are a very important antenna sub-system as they enable to reuse the same radiating aperture to produce all the beams. These solutions naturally find application in space as stringent accommodation constraints on board of satellites ask for space saving. Several concepts are available in the literature, including quasi-optic solutions and guided wave solutions. We investigated on this second category, including namely Blass, Butler and Nolen matrices as well as beam forming networks producing uniform phase distribution. In particular, we proposed a designed method, defined as an asymptotic singular case of a more general Blass matrix design procedure. Experimental validation was carried out with a specific design in S-band. Flexibility on the design of Nolen matrix has been used to generate non-uniform amplitude distribution to reduce side-lobe level. Also, natural phase dispersion of a serial feeding network has been used to produce frequency independent beam pointing linear arrays with potential application to Blass and Nolen matrices. Beam forming networks with uniform phase distribution associated to uniform and Gaussian amplitude distributions were also investigated, in particular to highlight the level of the intrinsic losses. The structure with Gaussian amplitude distribution was also modified to be adapted to circular array antennas. All this information should help to identify the best suited beam forming network concept for a given application. In some particular cases, a combination of different concepts can even be considered.

The aim of this study was to develop and examine the use of backscatter data collected with multibeam sonar (MBS) systems for benthic habitat mapping. Backscatter data were collected from six sites around the Australian coastal zone using the Reson SeaBat 8125 MBS system operating at 455 kHz. Benthic habitats surveyed in this study included: seagrass meadows, rhodolith beds, coral reef, rock, gravel, sand, muddy sand, and mixtures of those habitats. Methods for processing MBS backscatter data were developed for the Coastal Water Habitat Mapping (CWHM) project by a team from the Centre for Marine Science and Technology (CMST). The CMST algorithm calculates the seafloor backscatter strength derived from the peak and integral (or average) intensity of backscattered signals for each beam. The seafloor backscatter strength estimated from the mean value of the integral backscatter intensity was shown in this study to provide an accurate measurement of the actual backscatter strength of the seafloor and its angular dependence. However, the seafloor backscatter strength derived from the peak intensity was found to be overestimated when the sonar insonification area is significantly smaller than the footprint of receive beams, which occurs primarily at oblique angles. The angular dependence of the mean backscatter strength showed distinct differences between hard rough substrates (such as rock and coral reef), seagrass, coarse sediments and fine sediments. The highest backscatter strength was observed not only for the hard and rough substrate, but also for marine vegetation, such as rhodolith and seagrass. The main difference in acoustic backscatter from the different habitats was the mean level, or angle-average backscatter strength. However, additional information can also be obtained from the slope of the angular dependence of backscatter strength. / It was shown that the distribution of the backscatter. The shape parameter was shown to relate to the ratio of the insonification area (which can be interpreted as an elementary scattering cell) to the footprint size rather than to the angular dependence of backscatter strength. When this ratio is less than 5, the gamma shape parameter is very similar for different habitats and is nearly linearly proportional to the ratio. Above a ratio of 5, the gamma shape parameter is not significantly dependent on the ratio and there is a noticeable difference in this parameter between different seafloor types. A new approach to producing images of backscatter properties, introduced and referred to as the angle cube method, was developed. The angle cube method uses spatial interpolation to construct a three-dimensional array of backscatter data that is a function of X-Y coordinates and the incidence angle. This allows the spatial visualisation of backscatter properties to be free from artefacts of the angular dependence and provides satisfactory estimates of the backscatter characteristics. / Using the angle-average backscatter strength and slope of the angular dependence, derived by the angle cube method, in addition to seafloor terrain parameters, habitat probability and classification maps were produced to show distributions of sand, marine vegetation (e.g. seagrass and rhodolith) and hard substrate (e.g. coral and bedrock) for five different survey areas. Ultimately, this study demonstrated that the combination of high-resolution bathymetry and backscatter strength data, as collected by MBS, is an efficient and cost-effective tool for benthic habitat mapping in costal zones.

Viti Levu, the main island of Fiji, is located in a seismically active area within the Fiji Platform - a remnant island arc that lies in a diffuse plate boundary zone between the Pacific and Australian tectonic plates in the southwest Pacific. The southeast coast of Viti Levu is a highly developed and populated part of Fiji and is vulnerable to the effects of large earthquakes that are expected to occur both onshore and offshore. The structural framework and the origin of seismicity within the Fiji Platform, as well as the seismic and tsunami hazards of central and southeast Viti Levu are investigated. The upper crust of southeast Viti Levu is dissected by several intersecting fault/lineament zones. These are mapped from remote sensing imagery of the surface (topography, radar, and aerial photos) and of the basement (magnetic), and have been subject to rigorous statistical tests of reproducibility and verification with field mapped fault data. Lineaments on the various imagery correlate with faults mapped in the field and show spatial continuity between and beyond mapped faults, thereby providing a fuller coverage of regional structural patterns than previously known. Some fault/lineament zones extend beyond the coastline to the offshore area of southeast Viti Levu. Here high resolution SeaBAT 8160 multibeam bathymetry data and seismic reflection data show that the fault zones occur along, and exert control on the locations of a number of linear submarine canyons. The morpho-structural expression of these canyons are contiguous with fault controlled physiographic features mapped on the nearshore marginal shelf (rectilinear bays and peninsulas, reef passages) and on land (fault valleys, slope and drainage alignments forming lineaments). The canyons are considered to have developed from several cycles of downslope incising and infilling events, whilst their positions were still primarily controlled by zones of weakness created by the fault zones. The principal fault sets in southeast Viti Levu represent generations of regional tectonic faulting that pervaded the Fiji Platform during and after disruption of the proto Fijian arc in the Middle to Late Miocene. These fault sets combine to form a complex network of interlocking faults creating a fault mesh that divides the upper crust into a number of fault blocks ranging from ~2 to 30 km. It is inferred that the fault mesh evolved throughout the Neogene as a response to the anticlockwise rotation of the Fiji Platform through progressive development of different fault sets and intervening crustal block rotations. Regional tectonic deformation is presently accommodated in a distributed manner through the entire fault mesh. Low magnitude earthquakes (<M4) occur regularly and may represent ruptures along short linking segments of the fault mesh, while infrequent larger earthquakes (>M4) may result from complex rupture propagation through several linking fault segments of the mesh that lie close to optimum stress orientations. This interpreted model of distributed deformation through the fault mesh for southeast Viti Levu is inferred to be characteristic of the style of active deformation that occurs throughout the entire Fiji Platform. Seismic activity is primarily responsible for triggering submarine landslides that occur on the southeastern slope of Viti Levu. These slides typically occur on the outer barrier reef edge, as well as in submarine canyon heads and walls, and in the mid slope areas. They are characteristically translational and lack bathymetric evidence for displaced masses. Morphometric analysis and empirical modelling, show that slides triggered at shallow water depths, within 5 km of the coastline, at the outer barrier reef edge and submarine canyon heads, produce the largest near-field tsunami amplitudes. Such slides are interpreted to represent a significant local tsunami hazard. A detailed case study of the destructive 1953 Suva tsunami that followed the Ms 6.75 Suva earthquake, reveals that the source of this tsunami was a 60 million cubic metre submarine landslide at the head of the Suva Canyon, 4 km to the WSW of Suva City. A test simulation of this tsunami using the Geowave tsunami generation, propagation and inundation model, closely replicates the wave heights and arrival times recorded in 1953. This simulation also reveals that high variability in tsunami impact over short coastal distances of southeast Viti Levu is attributable to the complex interplay of wave propagation with the barrier reef system, erratic lagoon bathymetry and the irregularly shaped coastline. A predictive simulation using Geowave, based on an incipient failure in the 1953 source area and on a potentially worse case scenario event at or near high-tide, is used to show a maximum vertical run up of at least 4 m and a maximum horizontal inundation level of at least 400 m at the Suva coast. The seismic hazard of five sites on Viti Levu, including Suva City, Navua and Nausori Towns, and the Monsavu and Nadarivatu dam sites, is evaluated using a deterministic approach, and seven newly identified crustal fault earthquake source structures. The maximum magnitudes interpreted for these structures, estimated using empirical relationships, range from Mw 6.8 to 7.6. The Suva Canyon Fault, the Naqara Fault, the Mavuvu/Fault Lineament Zone and the Nasivi Fault provide the controlling maximum credible earthquakes (CMCE) at all the five sites. The CMCE peak ground acceleration values for Suva City range from 0.4g to 0.6g, for Nausori Town from 0.18g to 0.2g, for Navua Town from 0.27g to 0.32g, for Monasavu from 0.39g to 0.42g, and for Nadarivatu from 0.23g to 0.33g. The horizontal spectral accelerations at a period equal to 0.2 seconds, calculated using the CMCEs, are comparable to accelerations derived by probabilistic methods that have return periods between 50 and over 1000 years.

Cette thèse, co-dirigée par Jean-Marc Boucher et Ronan Fablet (IMT Atlantique) et co-encadrée par Didier Charlot (iXBlue), Gilles Le Chenadec et Michel Legris (ENSTA Bretagne), a été réalisée dans le cadre d'une convention CIFRE au sein de la société iXBlue. iXblue développe et commercialise un sondeur multifaisceaux (MBES) SEAPIX principalement dédié au marché de la pêche. Ce système a été développé pour offrir le meilleur compromis entre performances de détection et son coût de revient. Outre les caractéristiques classiques d'un MBES, il propose la particularité unique de pouvoir insonifier des fauchées différentes sous le navire par dépointage électronique du faisceau d'émission de bâbord à tribord et d'avant en arrière. Le travail de thèse a pour objectif d'étudier l'apport de ces nouvelles capacités multi-fauchées dans l'analyse et la classification des fonds marins. La première partie du travail a consisté à réaliser une analyse détaillée de la chaîne de mesure. Cette étude a permis d'évaluer la consistance des niveaux de rétrodiffusion entre les différents modes d'insonification. La deuxième partie s'est intéressée à la recherche des caractéristiques discriminantes du signal rétrodiffusé en tenant compte de la géométrie d'acquisition de chaque mode d'insonification. La dernière étape du travail a porté sur des méthodes de fusion des données acquises. Cette étude s'est réalisée en deux approches; la première considère des données venant du même mode d'insonification (intra-mode) et la seconde venant de modes différents (inter-mode), pour la cartographie des fonds marins. Les résultats expérimentaux obtenus mettent en évidence l'intérêt de la chaîne de traitement proposée et d'une architecture multi-mode sur les jeux de données réelles traitées. / This thesis, co-directed by Jean-Marc Boucher and Ronan Fablet (IMT Atlantique) and co-supervised by Didier Charlot (iXBlue), Gilles Le Chenadec and Michel Legris (ENSTA Bretagne), was realized in the context of a convention CIFRE with the company iXBlue.iXblue develops and commercializes a multibeam echosounder (MBES) SEAPIX primarily dedicated to the fishery market. The system is optimized to offer the best compromise between performances capabilities and cost. In addition to the classical characteristics of an MBES, it offers the unique feature of scanning the seafloor (and the water column volume) by electronical beamform multiple the emission swaths from port to starboard, as well as from forward to backward. The objective of the thesis is to study the contribution of these new multi-swath capacities in the analysis and classification of the seafloor.The first part of the work consisted in carrying out a detailed analysis of the measurement chain. This study evaluated the consistency in acquiring the backscattering strength from different insonification modes. The second part investigated the discriminant characteristics of the backscattered signal while taking into account the acquisition geometry of each insonification mode. The last stage of the work involved to methods of fusing the acquired data. This study was carried out in two approaches; the first considers data from the same insonification mode (intra-mode) and the second from different modes (inter-mode), for the seafloor classification. The obtained experimental results highlight the interest of the proposed processing chain and a multi-mode architecture on the real datasets.

This thesis investigates shallow gas hazards in Queen Charlotte Basin, a sedimentary basin situated offshore British Columbia. The work presented here provides the first detailed gas hazard assessment in Queen Charlotte Basin and the first evidence that gas has migrated from basin sediments into surficial sediments to be expelled in the water column. A unique method of geophysical surveying is used to investigate hazards due to shallow gas at two sites within Queen Charlotte Basin: high-resolution multichannel seismic, Huntec Deep-Towed Seismic and multibeam bathymetry data were collected over two 2-D grids and interpreted concurrently to yield a comprehensive understanding of the geology at each site. Numerous features related to both ice-cover and shallow gas has been identified. Pockmarks, iceberg ploughmarks and seafloor mounds are observed in the multibeam data; acoustically turbid and vertical blank zones are imaged in the Huntec data and faulted anticlines containing bright spots as well as low frequency shadow zones are seen in the multichannel data. Combining and interpreting all three geophysical datasets concurrently provided the means to discriminate features related to ice-cover from features related to gas in the shallow sediments. In addition, this method of geohazards assessment has enabled links between surficial and basin geology to be made. Based on the results obtained gas and other geohazards were identified at each of the two sites. Based on observations in high-resolution multichannel seismic data, gas is determined to have migrated along structural pathways within basin sediments and into surficial sediments. The level of hazard posed by shallow gas has been assessed qualitatively for each of the two study sites and gas hazard regions have been identified elsewhere in Queen Charlotte Basin.

La demande toujours croissante de connectivité et de débit de données requiert une rupture dans la conception des futurs réseaux de communication et systèmes radio. Plusieurs applications émergentes en bande millimétrique, notamment les réseaux mobiles de cinquième génération (5G) et les communications satellites, exigent des antennes large bande qui assurent une grande couverture angulaire, tout en étant à la fois compactes, facilement intégrables et à bas coût.Cette thèse propose des systèmes antennaires multifaisceaux large bande et à très grande couverture angulaire, appelés «Continuous Transverse Stub Antenna» (CTS), pour réaliser un bon compromis de l’ensemble de ces objectifs. L’architecture de l’antenne comprend un réseau de fentes longues excitées par un réseau d’alimentation en chandelier, basé sur des guides d’onde à plans parallèles. Cette structure est excitée par un formateur de faisceaux quasi-optique co-intégré. La première partie du manuscrit présent des nouveaux modèles numériques qui facilitent la conception de chaque sous-système de l’antenne et permettent l’analyse des performances globales, soit en termes d’adaptation, soit en termes de diagrammes de rayonnement. Ces outils sont exploités pour la conception d’antenne et pour étudier les limites en balayage. La thèse se poursuit en présentant de nouvelles solutions technologiques et de nouveaux design pour intégrer les antennes CTS dans des modules multicouches planaires et à faible profil. La conception et la caractérisation de deux antennes intégrées en technologie LTCC pour des points d’accès 5G à 60 GHz sont discutées. L’une des deux est à faisceau fixe, l’autre est à balayage électronique, avec une couverture de ±40°, de faibles lobes secondaires et un niveau élevé de recoupement des faisceaux. Enfin, nous proposons l’association de radomes polarisants planaires à faible profil aux antennes CTS, pour réaliser des systèmes rayonnants en polarisation circulaire. Une méthodologie systématique pour la conception de polarisateurs à très large bande est présentée, ainsi qu’un design couvrant entièrement la bande Ka pour des applications satellites. / The ever-growing demand for fast and seamless connectivity shows the need of new wireless standards and technologies. Novel broadband, wide-angle scanning antennas achieving an optimal trade-off among size, gain, efficiency and costs are crucial to the development of emerging applications at millimeter waves, such as fifth-generation (5G) mobile networks and satellite communications. In this thesis, multibeam parallel-fed continuous transverse stub (CTS) array antennas are proposed as possible candidates for future mm-wave communications and are developed to tackle these requirements. The antenna architecture comprises an array of long slots, a corporate feed network based on parallel plate waveguides (PPWs) and an integrated quasi-optical beamformer. First, novel numerical models for the analysis of each subsystem and of the overall antenna, are presented, which enable an efficient and modular design of CTS antennas. These tools are exploited to derive design guidelines and assess the scanning performance. Then, novel design and technological solutions for the integration of CTS antennas in flat, low-profile multilayer modules are discussed. The design and characterization of two prototypes in LTCC technology, for 60-GHz mobile access points are presented: a fixed beam array and a switched-beam antenna with a field of view of ±40°, low SLLs and high beam overlap. Finally, planar linear-to-circular polarization converters are proposed to realize circularly polarized CTS antenna systems. A procedure to achieve an ultra-wideband, low-loss polarization conversion is outlined and a design for Ka-band satellite application is presented.