Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis is about the design, simulation and measuring of ultra wide band antennas for use in the Square Kilometre Array (SKA). The SKA is a radio astronomy project with one of the aims of detecting hydrogen particles in deep space. Several thousand antennas over a wide band of frequencies are needed to receive the radiation from these particles. This motivates the need for a low-cost ultra wide band antenna with the focus on the low frequency part of the SKA. In this thesis we present two design strategies: The first design strategy is for a printed LPDA on a substrate and design curves are generated. A scale model was built and measurements did not correlate with simulation results. This is due to manufacturing tolerances and assembly of the pyramidal structure. The second design strategy is for a full scale zig-zag antenna and design curves were also generated. The aim here is to produce a low-cost prototype by using brazing rods for the wire structure and mount it on a wooden frame. A full scale model was built and measurements on the roof produced much interference for the radiation pattern, but the reflection coefficient was good. We suggest doing measurements in an interference free environment in order to achieve the needed results. To conclude we suggest using the zig-zag antenna for the SKA. Some issues do however need more attention as the transformer has some losses, the cross polarisation is probably not good enough and the beamwidth does not reach the specification. We demonstrated a low cost prototype and there is the possibility of low-cost large scale manufacturing but this needs to be addressed. This has however not been analysed as many factors for large scale manufacturing are very difficult to predict beforehand and lies outside the scope of this thesis. / AFRIKAANSE OPSOMMING: Hierdie tesis gaan oor die ontwerp, simulasie en opmeting van ultrawyebandantennas vir gebruik in die SKA ("Square Kilometre Array"). Die SKA is ’n radioastronomie projek met die doel om waterstof partikels op te spoor in die ruimte. Duisende antennas wat oor ’n wye band van frekwensies strek is nodig om die energie van die partikels op te vang. Hieruit is daar ’n aanvraag vir lae-koste ultrawyebandantennas met die fokus op die lae frekwensie deel van die SKA. In hierdie tesis word twee ontwerpstrategieë voorgestel: Die eerste ontwerpstrategie is vir ’n gedrukte logaritmies periodiese dipool reeks (LPDR) op ’n substraat tesame met ontwerpskurwes wat gegenereer word. ’n Skaal model is gebou en die gemete resultate stem nie ooreen met die simulasie nie. Dit kan toegeskryf word aan vervaardigingstoleransies en die aanmekaar sit van die piramide struktuur. Die tweede ontwerpstrategie is vir ’n vol skaal sigsag ("zig-zag") antenna met ontwerpskurwes wat ook gegenereer word. Die doel is om ’n lae-koste prototipe te bou deur sweissoldeerdraad te gebruik vir die draadstruktuur en dan op ’n hout raam te plaas. ’n Vol skaal model is gebou en metings op die dak het baie interferensie veroorsaak vir die stralingsveld, maar tog was die weerkaatskoëffisient goed. Ons stel voor om die metings te herhaal in ’n steuringvrye omgewing om sodoende die korrekte resultate te verkry. Om af te sluit stel ons voor om die sigsag antenna vir die SKA te gebruik. Sekere kwessies soos die transformator wat verlieserig is, die kruispolarisasie wat moontlik nie goed genoeg is nie en die bundelwydte wat nie die spesifikasie haal nie moet nog aandag geniet. Ons het ’n lae-koste prototipe gedemonstreer en daar is die moontlikheid om dit op grootskaalse vervaardiging ook goedkoop te doen, maar dit moet nog uigesorteer word. Dit was wel nie geanaliseer nie, siende dat vele faktore ’n rol speel by grootskaalse vervaardiging wat uiters moeilik is om voor die tyd te voorspel en buite die omvang van die tesis lê.

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No. of bitstreams: 1 AlexandreHSO_DISSERT.pdf: 4241907 bytes, checksum: 7c578927aa89afb44e48b7e51e99d120 (MD5) Previous issue date: 2017-04-07 / Fundação de Apoio à Pesquisa do RN / The knitted fabrics have elastic, easy production and malleability properties, these characteristics be useful in the design of flexible antennas, that can be used in a RFID tag, for example. The mean objective of this work is development of antenna with a Coplanar Waveguide fed (CPW), in a textile knitted substrate, for use in active RFID systems in microwave frequency of 2.45 GHz. From the characterization of the electrical properties by a Vector Networks Analyzer and one with a Dielectric Probe kit, obtained the values of Electrical Permissiveness and Loss Tangent, in sequence was carried out the characterization of the textile properties of Linear Density, Basis weight, Dimensional stability and Tensile Strength, based on the data obtained in characterization process, was chosen two fabrics with properties favorable to the design, modeling and construction of antennas. After the selection of the tissues, simulations were performed on Ansys HFSStm (High Frequency Structural Simulator) to obtain the parameters of Return Loss, Radiation Diagram, Current Density, Impedance, Gain and VSWR, as well as dimensional optimization of the antennas. Two CPW-fed antennas were simulated, one on textile substrate made from Soybean Protein Fibers (SPF) and the other with Polypropylene with corn Polylactic Acid fibers (PP + PLA). Based on the simulations, two antennas with their respective textile substrates were constructed and using a vector network analyzer, the return loss and the impedance shown by the Smith Chart were measured. Both showed a return loss below -10dB for central design frequency and wide bandwidth. The simulated and measured results were compared, analyzing them according to the specialized reading in the area. Showing the feasibility of developing CPW antennas in knitted fabrics for active RFID systems, in addition to the possibility of interoperability in internet of things (IoT) communication systems / Os tecidos de malha apresentam propriedades de elasticidade, facilidade de fabricação e maleabilidade, devido a estas características a utilização desse tipo de tecido traz vantagens na fabricação de antenas para aplicação no desenvolvimento de uma tag RFID. O presente trabalho tem como objetivo desenvolver antenas com guias de ondas coplanares (CPW), em substrato têxtil em estruturas de malha, para utilização em sistemas ativos de Identificação por Rádio Frequência, RFID, para frequência de operação em micro-ondas de 2,45 GHz. Foi realizada a caracterização das propriedades elétricas por meio de um Analisador de Redes Vetoriais e com uma sonda de medição de matérias dielétricos, obtive-se então os valores de Permissividade elétrica e Tangentes de perdas, em sequência foi realizada a caracterização das propriedades têxteis de Título, Gramatura, Estabilidade Dimensional e Resistência a tração, com base nos dados obtidos no processo de caracterização se elegeu dois tecidos com propriedades favoráveis ao projeto, modelagem e construção das antenas têxteis. Após a seleção dos tecidos foram feitas simulações no Ansys HFSS® (High Frequency Strucutural Simulator) para obtenção dos parâmetros de Perda de retorno, Diagrama de radiação, Densidade de corrente, Impedância, Ganho e VSWR, além da otimização dimensional das antenas. Foram simuladas duas antenas CPW, uma em substrato têxtil feito de fibras de Proteína de Soja (SPF) e outra com fibras de Polipropileno com Ácido Polilático de Milho (PP+PLA). Com base nas simulações foram construídas duas antenas com os respectivos substratos têxteis e utilizando um analisador de redes vetoriais foram medidos a perda de retorno e a impedância, mostrada por meio da Carta de Smith. Ambas apresentaram uma perda de retorno abaixo de -10 dB para frequência central de projeto e uma alta largura de banda. Foi realizada a comparação dos resultados simulados e os efetivamente medidos, analisando-os de acordo com a literatura especializada na área. Mostrando a viabilidade do desenvolvimento de antenas CPW em tecidos de malha para sistemas RFID ativos, além da possibilidade da interoperabilidade em sistemas de comunicação por Internet das coisas, Internet of Things, IoT / 2017-07-10

Made available in DSpace on 2014-12-17T14:55:12Z (GMT). No. of bitstreams: 1 ManoelBLA.pdf: 2395577 bytes, checksum: 6394225c6ebbbdad59d4fa162aa97882 (MD5) Previous issue date: 2008-11-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This paper presents a theoretical and numerical analysis of the parameters of a rectangular microstrip antenna with metamaterial substrate. The metamaterial (MTM) theory was applied along with Transverse Transmission Line (LTT) method to characterize substrate quantities and obtain the general equations of the electromagnetic fields. A study on metamaterial theory was conducted to obtain the constructive parameters, which were characterized through permittivity and permeability tensors to arrive at a set of electromagnetic equations. Electromagnetic principes are used to obtained parameters such as complex resonance frequency, bandwidth and radiation pattern were then obtained. Different metamaterial and antenna configurations were simulated to miniaturize them physically and increase their bandwidth, the results of which are shown through graphics. The theoretical computational analysis of this work proved to be accurate when compared to other studies, and may be used for other metamaterial devices. Conclusions and suggestions for future work are also proposed / Este trabalho apresenta a an?lise te?rica e num?rica dos par?metros de uma antena de microfita tipo patch retangular sobre substrato metamaterial. Para isso, ? aplicada a teoria de metamateriais - MTM, em conjunto com o m?todo da Linha de Transmiss?o Transversa - LTT, para a caracteriza??o das grandezas do substrato e obten??o das equa??es gerais dos campos eletromagn?ticos. ? realizado um estudo acerca da teoria de metamateriais com o intuito de obter seus par?metros construtivos, os mesmos s?o caracterizados atrav?s de tensores permissividade e permeabilidade. Essa teoria ? aplicada ao m?todo da Linha de Transmiss?o Transversa chegando-se ?s equa??es gerais para os campos eletromagn?ticos da antena. Em seguida s?o utilizados princ?pios da teoria eletromagn?tica para obter-se caracter?sticas como: freq??ncia de resson?ncia complexa, diagramas de radia??o e largura de banda. S?o simulados diferentes configura??es de metamateriais e antenas com o intuito de miniaturizar as dimens?es f?sicas e aumentar a largura de banda das mesmas, os resultados s?o apresentados atrav?s de gr?ficos. A an?lise te?rica computacional deste trabalho se mostra precisa, em compara??o a outros, podendo ser empregado em dispositivos que utilizem metamateriais como substratos. Ao final s?o apresentadas conclus?es e sugest?es para trabalhos futuros

Made available in DSpace on 2014-12-17T14:55:43Z (GMT). No. of bitstreams: 1 ValdezAAFi_DISSERT.pdf: 1620850 bytes, checksum: c1208b8ca13742d0d9cd3ac88c864f60 (MD5) Previous issue date: 2010-06-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work aims to present how the application of fractal geometry to the elements of a log-periodic array can become a good alternative when one wants to reduce the size of the array. Two types of log-periodic arrays were proposed: one with fed by microstrip line and other fed by electromagnetic coupling. To the elements of these arrays were applied fractal Koch contours, at two levels. In order to validate the results obtained some prototypes were built, which were measured on a vector network analyzer and simulated in a software, for comparison. The results presented reductions of 60% in the total area of the arrays, for both types. By analyzing the graphs of return loss, it was observed that the application of fractal contours made different resonant frequencies appear in the arrays. Furthermore, a good agreement was observed between simulated and measured results. The array with feeding by electromagnetic coupling presented, after application of fractal contours, radiation pattern with more smooth forms than the array with feeding by microstrip line / Este trabalho tem como objetivo apresentar como a aplica??o de contornos fractais aos elementos de um arranjo log-peri?dico se torna uma alternativa bastante interessante quando se deseja reduzir as dimens?es do arranjo. Foram propostos dois tipos de arranjos log-peri?dicos: um com alimenta??o por linha de microfita e outro com alimenta??o por acoplamento eletromagn?tico. Aos elementos desses arranjos foram aplicados contornos fractais de Koch, em dois n?veis. Com a finalidade de validar os resultados obtidos foram constru?dos prot?tipos, que foram caracterizados experimentalmente em um analisador de rede vetorial e simulados em software, para compara??o. Os resultados mostraram redu??es de 60% nas dimens?es dos arranjos, para ambos os tipos. Atrav?s da an?lise dos gr?ficos da perda de retorno, p?de-se observar que a aplica??o dos contornos fractais fez com que aparecessem diferentes frequ?ncias de resson?ncia nos arranjos. Al?m disso, observa-se uma boa concord?ncia entre os resultados medidos e simulados. O arranjo com alimenta??o por acoplamento eletromagn?tico apresentou, ap?s aplica??o dos contornos fractais, menores valores de diretividade do que o arranjo com alimenta??o por linha de microfita

Made available in DSpace on 2014-12-17T14:55:53Z (GMT). No. of bitstreams: 1 JoseHCM_DISSERT.pdf: 1439414 bytes, checksum: f96f0decdde25078b5110927edf3b75c (MD5) Previous issue date: 2011-12-19 / This work presents techniques used to design and manufacture microstrip patch antennas for applications in portable and mobile devices. To do so, are evaluated several factors that can influence the performance of microstrip patch antennas. Miniaturization techniques are studied and employed in order to apply this type of antenna in mobile and / or mobile. The theories of microstrip patch antennas are addressed by analyzing characteristics such as constitution, kinds of patches, substrates, feeding methods, analysis methods, the main advantages and disadvantages and others. Techniques for obtaining broadband microstrip patch antennas were surveyed in literature and exemplified mainly by means of simulations and measurements. For simulations of the antennas was used the commercial software . In addition, antenna miniaturization techniques have been studied as a main concern the fundamental limits of antennas with special attention to electrically small antennas because they are directly linked to the microstrip patch antennas. Five design antennas are proposed to demonstrate the effectiveness of techniques used to obtain the microstrip patch antennas broadband and miniaturized for use in mobile devices and/or portable. For this, the proposed antennas were simulated, built and measured. The antennas are proposed to be used in modern systems of wireless communications such as DTV, GPS, IEEE 802.16, IEEE 802.11, etc. The simulations of the antennas were made in business and computer programs. The measured results were obtained with a parser Vector of networks of the Rhode and Schwarz model ZVB 14 / Esse trabalho apresenta t?cnicas usadas para projetar e fabricar antenas patch de microfita para aplica??es em dispositivos port?teis e m?veis. Para isso, s?o avaliados diversos fatores que podem influenciar no desempenho das antenas patch de microfita. T?cnicas de miniaturiza??o s?o estudadas e empregadas visando a aplica??o deste tipo de antena em dispositivos port?teis e/ou m?veis. Fundamentos te?ricos sobre as antenas patch de microfita s?o abordados analisandose caracter?sticas como: constitui??o, tipos de patches, substratos, m?todos de alimenta??o, m?todos de an?lises, principais vantagens e desvantagens dentre outros. T?cnicas para obten??o de antenas patch de microfita banda larga foram pesquisadas na literatura e exemplificadas principalmente por meio de simula??es e medi??es. Para as simula??es das antenas foi utilizado o programa computacional comercial . Al?m disso, t?cnicas de miniaturiza??o de antenas foram estudadas tendo como preocupa??o principal os limites fundamentais das antenas com aten??o especial a antenas eletricamente pequenas por estarem diretamente vinculadas ?s antenas patch de microfita. Cinco projetos de antenas s?o propostos para comprovar a efici?ncia das t?cnicas utilizadas para obten??o de antenas patch de microfita banda larga e miniaturizadas, para aplica??o em dispositivos m?veis e/ou port?teis. Para isso, as antenas propostas foram simuladas, constru?das e medidas. As antenas foram propostas para serem utilizadas em sistemas modernos de comunica??es sem fio como: DTV, GPS, IEEE 802.16, IEEE 802.11, etc. As simula??es das antenas foram feitas nos programas computacionais comerciais e . Os resultados medidos foram obtidos com um analisador vetorial de redes da Rhode and Schwarz modelo ZVB 14

Dans les systèmes de communication et de détection sans fil, l'antenne est un élément indispensable pour transformer l'énergie électrique en ondes électromagnétiques rayonnée dans l'espace, et vice versa. Les antennes sont utilisées dans de nombreux dispositifs militaires et civils, tels que les radars (SAR, secteur automobile, détection de débris, etc.), les instruments biomédicaux, les systèmes de télécommunication (téléphones mobiles, stations de base) pour les communications point à multi-point ou point à point par exemple. Les antennes jouent aussi un rôle essentiel pour le développement de futurs réseaux connectés reliant plusieurs appareils à des utilisateurs en temps réel, par exemple pour l'Internet des objets (IoT). Les réseaux transmetteurs sont une solution attrayante pour de nombreuses applications telles que les communications par satellite (Satcom) ou les futurs réseaux 5G. L'architecture des antennes à réseau transmetteur les rend extrêmement compétitifs comparés aux réseaux phasés par exemple grâce à leur alimentation par onde d’espace et car ils ne souffrent pas du blocage induit par la source primaire, comme c’est le cas pour les réseaux réflecteurs ou les antennes à réflecteur. Grâce à leur fonctionnement en mode transmission, les réseaux transmetteurs peuvent être également facilement montés sur des plates-formes mobiles.Les applications Satcom en bande Ka constituent le secteur applicatif majeur de cette thèse. Cette bande fournit un débit de données élevé à la fois pour les liaisons descendantes et les liaisons montantes, en remplacement des systèmes actuels en bande Ku. Dans ce contexte, il convient aussi de prêter une attention particulière aux communications avec des plates-formes mobiles, par exemple les trains à grande vitesse, les avions, etc., ce qui nécessite de mettre au point des antennes à balayage de faisceau. De nombreuses propriétés avancées sont exploitées depuis ces dernières années pour accroître les débits et la flexibilité des systèmes de communication sans fil, par exemple la polarisation circulaire, la double polarisation, le fonctionnement multi-fréquence ou large bande, le dépointage électronique de faisceau. Pour réduire les coûts, des preuves de concept de réseaux transmetteurs non diélectriques sont également proposées. Cette thèse s’est déroulée dans le cadre du projet ANR TRANSMIL (Reconfigurable TRANSmitarrays for beam steering and beam forming at MILlimetre wave). Les objectifs de cette thèse sont de proposer de nouvelles architectures de réseaux transmetteurs fonctionnant en bande Ka en liaison descendante (de 17,7 GHz à 21,2 GHz) et en liaison montante (de 27,5 GHz à 31 GHz). Différents prototypes ont été conçus et fabriqués afin de valider les concepts proposés en bande X et en bande Ka. Un bon accord entre les résultats numériques et mesurés a été obtenu systématiquement. En particulier, les réseaux transmetteurs à double polarisation que nous avons conçus en bande X présentent un gain de 25 dBi et une bande passante à 3 dB de 20% à 10 GHz. Ces propriétés sont indépendantes de la polarisation du champ rayonné, ce qui signifie que des faisceaux de polarisation linéaire orthogonale peuvent être rayonnés indépendamment dans des directions différentes. Un réseau transmetteur bi-bande fonctionnant en bande Ka a également été mis au point. Sa bande passante à 3 dB est de 10% autour des fréquences centrales (19,5 GHz et 29 GHz) et son efficacité de rayonnement atteint 60%. D’autres concepts ont également été étudiés (réseaux transmetteurs sans diélectrique, réseau transmetteur reconfigurable). / Transmitarray is an attractive solution for front-end devices in the next generation of communications (5G). The spatial-fed architecture of transmitarray antennas can compete with phase-arrays due to the absence of feeding network and with reflectarrays since they do not suffer from feed blockage. Thanks to their operation in transmission mode, transmitarrays can be easily mounted on platforms for outdoor environment applications. With mature printed-circuit board technology, there are unstoppable experiments in various frequency bands from cm-wave to mm-wave and up to terahertz in upcoming years for potential applications. Many advanced properties are exploited in transmitarrays in recent years to meet high demands of communications facilities, for example, circular-polarization, dual-/multi-polarization or frequencies through many techniques. Some experiments are consid-ered to validate eligibility of this antenna type in commercial services or military missions, namely electronically steering beam, broad bandwidth, etc. In terms of cost reduction and rigidity, non-dielectric prototypes are also proposed. The Ka-band Satcom applications are the main objective of this thesis through trans-mitarray solution. This band provides high data rate for both down-link and up-link in replacement of the current Ku-band systems with miniaturized module in next dec-ades. Hence, it is worth to pay attention to communications for moving platforms, for example, high-speed trains, planes, etc.

Les antennes à polarisation circulaire (CP) sont de plus en plus utilisées dans les systèmes de communications spatiaux et terrestres. Le besoin d’intégration est sans cesse plus important, il est donc nécessaire de proposer, de mettre au point des aériens toujours plus compacts et aux performances (adaptation, rayonnement, gain, efficacité, taux d’ellipticité) optimisées. L’objectif de cette thèse est donc de concevoir des antennes planaires, large bande ou multi-bande, à polarisation circulaire et aux performances optimisées. Afin d’atteindre ces objectifs, le travail a été divisée en plusieurs phase, allant de la conception d’une antenne CP à large bande jusqu’à la conception d’une antenne patch à polarisation circulaire tri bandes GNSS. Tout d’abord une étude bibliographique sur les antennes planaires a été faite. Celle-ci a permis de comparer leurs différentes performances, leurs avantages et inconvénients. Ensuite, une antenne patch CP à éléments parasites a été conçue fabriquée et mesurée. On s’est attaché à optimiser sa bande de fonctionnement. En tenant compte des études bibliographiques déjà faites, et en se basant sur la structure de l’antenne CP à large bande validée lors de la phase précédente, une nouvelle antenne plaquée CP GNSS tri bandes a également été conçue réalisée et mesurée. L’essentiel du travail a consisté à minimiser son encombrement tout en conservant des performances électromagnétiques satisfaisantes dans les trois bandes de fréquences objectifs : L2, E6 et L1. On s’est particulièrement attaché à obtenir un bon taux d’ellipticité sur une large ouverture rayonnante. La dernière étape de cette thèse a consisté à aller encore plus loin dans l’amélioration des performances de l’antenne CP GNSS multi bandes particulièrement en améliorant son efficacité. Une excitation par fente a finalement été utilisée après comparaison des performances obtenues via différentes techniques (alimentation coaxiale, fentes, etc…). / Circular polarized antennas (CP) are greatly used in space and terrestrial communication systems. Furthermore, the need for communication systems integration is increasingly important. Therefore, it is necessary to propose and develop more compact antenna design with optimized performance (adaptation, radiation, gain, efficiency, axial ratio).The objective of this thesis is to design planar antennas, broadband or multi-band, with circular polarization and optimized performances. To achieve these objectives, the work was divided into several stages, from the design of a wideband CP antenna to the design of a GNSS tri-band circular polarized patch antenna. Firstly, a literature study of planar antennas has been conducted. Different designs have been examined and contrasted to evaluate their performances. Secondly, a wideband CP patch antenna with parasitic elements has been designed manufactured and measured. It was sought to optimize its operating band. Considering the bibliographical study that was already carried out, and based on the wideband CP antenna structure that was validated during the previous phase, a new GNSS tri-band CP patch antenna was also designed, fabricated and measured. Most of the work was done on minimizing its size while maintaining satisfactory electromagnetic performance in the three required GNSS frequency bands : L2, E6 and L1. Special attention was directed towards getting a good axial ratio over a wide radiating aperture. The last phase of this thesis was to go even further in improving the CP GNSS multi-band antenna's performance, particularly by improving its efficiency. Excitation slots were finally used after a comparison was made between the different performances obtained through the different design techniques (coaxial feed, slots, etc ...).

No description available.

Frequency-domain scheduling, multiple antenna techniques, and rate adaptation enable next generation orthogonal frequency division multiple access (OFDMA) cellular systems such as Long Term Evolution (LTE) to achieve significantly higher downlink spectral efficiencies. However, this comes at the expense of increased feedback overhead on the uplink. LTE uses a pragmatic combination of several techniques to reduce the channel state feedback required by a frequency-domain scheduler. In subband-level feedback scheme specified in LTE, the user reduces feedback by only reporting the channel quality indicator (CQI) computed over groups of resource blocks called subbands. LTE also specifies an alternate user selected subband feedback scheme, in which the feedback overhead is reduced even further by making each user feed back the indices of the best M subbands and only one CQI value averaged over all the M subbands. The coarse frequency granularity of the feedback in the above schemes leads to an occasional incorrect determination of rate by the scheduler for some resource blocks. The overall throughput of LTE depends on the method used to generate the CQI and the statistics of the channel, which depends on the multiple antenna technique used. In this thesis, we develop closed-form expressions for the throughput achieved by the user selected and subband-level CQI feedback schemes of LTE. The comprehensive analysis quantifies the joint effects of four critical components on the overall system throughput, namely, scheduler, multiple antenna mode, CQI feedback scheme, and CQI generation method. The performance of a wide range of schedulers, namely, round robin, greedy, and proportional fair schedulers and several multiple antenna diversity modes such as receive antenna diversity and open-and closed-loop transmit diversity is analyzed. The analysis clearly brings out the dependence of the overall system throughput on important parameters such as number of resource blocks per subband and the rate adaptation thresholds. The effect of the coarse subband-level frequency granularity of feedback is explicitly captured. The analysis provides an independent theoretical reference and a quick system parameter optimization tool to an LTE system designer. It also helps us theoretically understand the behavior of OFDMA feedback reduction techniques when operated under practical system constraints. Another contribution of this thesis is a new statistical model for the effective exponential SNR mapping (EESM), which is a highly non-linear mapping that is widely used in the design, analysis, and simulation of OFDMA systems. The statistical model is shown to be both accurate and analytically tractable, and plays a crucial role in facilitating the analysis of the throughput of LTE when EESM is used to generate the CQI.

La télémédecine et plus particulièrement la télémédecine mobile semble représenter l’avenir en termes de soins médicaux. Ce concept nécessite cependant pour sa viabilité, de disposer d’éléments rayonnants miniatures, fortement efficaces, et capables de communiquer sur plusieurs bandes. Ce mémoire présente la méthodologie de conception et l’optimisation d’antennes miniatures intégrées, dédiées à un dispositif spécifique permettant de réaliser une liaison radiofréquence entre un implant médical et le téléphone portable d’un patient. Cependant, la miniaturisation des antennes, éléments clés de ce concept, s’accompagne généralement d’une dégradation de son efficacité et de sa bande passante, ce qui rend délicat leur mise en œuvre sur au moins deux des points essentiels recherchés. La conception de ce type d'antennes nécessite donc une analyse très fine des phénomènes physiques mis en jeu dont notamment la limite théorique en termes de performances que l'on peut atteindre pour une antenne circonscrite à un volume donné. De plus, ces performances radioélectriques sont fortement dépendantes de l'environnement dans lequel est placée l’antenne. Par conséquent, l'influence de chaque partie constituant cet environnement doit être prise en compte lors de l'intégration, ce que nous décrivons également dans ce manuscrit à travers différentes solutions d’éléments rayonnants. / This thesis presents the design and the optimization of miniature antennas integrated in specific devices dedicated to ensure communications between medical implants and a mobile phone in the context of telemedicine applications. However, the miniaturization of antennas necessarily implies a degradation of efficiency and bandwidth, which makes it difficult for implementation. Then, the design of electrically small antennas requires a very good understanding of the physical phenomena such as the theoretical limits of performance in terms of bandwidth and efficiency that can be expected for a radiating element with given dimensions. Furthermore, the performance of an electrically small antenna is also highly dependent on the environment in which it is mounted. Therefore, its interaction with each part of its close environment was highlighted and analyzed.