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Dissertations / Theses on the topic 'Antennas'

Author: Grafiati
Published: 4 June 2021
Last updated: 7 September 2024

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1

Rouibah, Ammar. "Un modèle analytique pour l'antenne microruban rectangulaire." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209359.

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Les antennes microruban et en particulier l’antenne microruban rectangulaire sont étudiées et utilisées depuis plusieurs dizaines d’années.

Comme pour toute antenne, il est important de disposer pour ces antennes d’un modèle analytique qui permette une bonne compréhension du fonctionnement et fournisse de manière rapide des valeurs pour les principaux paramètres (fréquence de travail, impédance, gain, rendement et bande passante).

Au fil des ans, deux modèles, chacun comprenant de nombreuses variantes, ont été développés :le modèle dit « de la ligne de transmission » et le modèle dit « de la cavité ». Ces modèles sont soit peu rigoureux, soit complexes et donnent souvent des résultats assez éloignés de la réalité.

L’objectif de ce travail est double :définir un modèle qui soit d’une part aussi simple et direct que possible et d’autre part aussi précis que possible.

Le premier objectif est atteint dans la mesure où on n’utilise que la loi fondamentale du rayonnement des courants réels (électriques) en excluant tout recours à des courants virtuels (magnétiques).

Concernant l’objectif de précision, des comparaisons nombreuses avec des résultats d’un simulateur purement numérique et des mesures indiquent une amélioration pour tous les paramètres mais en particulier pour l’impédance qui est le point faible de tous les modèles existants.

Microstrip antennas and the rectangular microstrip antenna in particular have been studied and used for several decades.

As every antenna, the microstrip antenna requires a good analytical model that provides physical insight and an easy prediction of the antenna parameters (resonance frequency, impedance, gain, efficiency and bandwidth).

Over the years, two families of models have been developed, each involving many variants: the “transmission line” and the “cavity” models. These models either lack accuracy or are very complex and produce results that may be far away from reality.

The objective of this work is double: defining a model as simple and direct as possible and on the other hand as accurate as possible.

The first objective has been reached as all our calculations rest on the fundamental radiation formula by real (electrical) currents excluding any virtual (magnetic) currents.

Regarding accuracy, comparisons to numerical simulations and measurements show an improvement, in particular with regard to the prediction of the impedance parameters, which is the weak point of all existing models.


Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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2

Sonkki, M. (Marko). "Wideband and multi-element antennas for mobile applications." Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526201085.

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Abstract This dissertation presents wideband and multi-element antennas for mobile applications. It is divided into the following main parts: modal theory, wideband antennas, multi-element antennas, and wideband multi-element antennas. The radiating fields are first studied in terms of spherical scalar and vector modes, and it is shown how these modes correlate with the characteristic current modes on a planar mobile ground plane. The theory part shows how it is possible to excite the same modes on a conventional sphere and a rectangular planar mobile ground plane. The theory refers to the novel wideband antenna structures presented in this dissertation, in terms of current and radiating modes. After studying the modes, the dissertation shows how to excite a radiating antenna mode within a wide frequency bandwidth. To gain this, two main approaches are taken. First, a quasi-complementary antenna (QCA) structure with an electric conductor and magnetic slot is presented, and its characteristics are studied. A QCA UWB antenna, and a QCA element excited with a monopole or a dipole, is presented. The QCA structure compensates for the imaginary part of the input impedance on wide frequency bandwidth, when, at the same time, the fundamental mode is excited to ensure good radiating properties. The second approach uses a symmetrical feeding with two antenna elements to gain a wide frequency bandwidth, the relative -6 dB impedance bandwidth between 37.5–80%. When a field is symmetrically coupled to the conducting ground plane, the excitation avoids the awakening of higher order modes which might disturb the performance of the antenna. It is also shown, by using multiple feeding elements, that the excitation of orthogonal higher order modes on a small radiating ground plane is possible. As the modes are orthogonal to each other, they present a very low correlation. By using this kind of approach, radiation pattern diversity can be obtained in mobile applications within a small volume. On the other hand, when combining two QCA elements to a one multi-element antenna structure, a wideband diversity antenna with an 87.5% relative -6 dB impedance bandwidth, and a wideband MIMO antenna with a 95.0% relative -6 dB impedance bandwidth, are presented with excellent radiation and correlation properties. Also mutual coupling is need to be counted when multi-element antennas are designed. When designing an efficient radiator, it is important to consider an antenna feeding in terms of wideband impedance matching and wideband baluns, not to spoil the antenna performance. The efficient antenna structures and feeding mechanisms are obtained by using commercial 3D electromagnetic simulators to find the desired wideband antenna characteristics. Prototype antennas are measured in most of the presented structures to show their functionality in real. In general, the dissertation presents wideband antenna structures with radiating antenna modes excited on a planar conducting ground plane. The idea is to find structures and feeding mechanisms to excite the fundamental mode, or a certain radiating antenna mode, at a wide frequency bandwidth, by avoiding the excitation of higher order modes which might disturb the antenna performance. It is also shown that, by using multiple feeding elements, it is possible to excite higher order modes on a small antenna
Tiivistelmä Väitöskirjassa esitetään uusia laajakaistaisia ja monielementtiantenneja matkaviestimiin. Väitöskirja koostuu neljästä pääalueesta: pintavirtojen muototeoria, laajakaistaiset antennit, monielementtiantennit sekä laajakaistaiset monielementtiantennit. Teoriaosassa säteilykenttiä on aluksi tutkittu pallon pinnalla sekä skalaaripotentiaaleina että pintavirtavektoreina, jonka jälkeen niitä on verrattu mobiilin laitteen maatason ominaispintavirtojen synnyttämiin säteilykenttiin. Teoriaosassa osoitetaan, että pallon pinnalla sekä tasomaisella suorakaiteen muotoisella pinnalla on mahdollista herättää samat säteilykentät. Myöhemmin väitöskirjassa esitettävien uudenlaisten antennirakenteiden ominaisuuksia verrataan teoriaosassa esitettyihin pintavirtoihin ja säteilykenttiin. Teoriaosuuden jälkeen osoitetaan miten säteilevä sähkömagneettinen kenttä saadaan herätettyä laajalla taajuusalueella. Tähän on otettu kaksi eri lähestymistapaa, joista ensimmäisessä esitellään ja tutkitaan kvasikomplementaarista antennirakennetta (QCA). Kvasikomplementaarisessa antennirakenteessa sisääntuloimpedanssin imaginaariosa kompensoidaan yhdistämällä sähköinen johde ja magneettinen rako samaan antenniin. Samanaikaisesti perusmuoto herätetään laajalla taajuusalueella, jolla varmistetaan antennin hyvät säteilyominaisuudet koko toimintataajuusalueella. Toisessa lähestymistavassa käytetään kahta symmetrisesti asetettua antennielementtiä, joita syötetään symmetrisesti samalla amplitudilla ja vaiheella. Kun sähkömagneettinen kenttä herätetään symmetrisesti, korkeamman kertaluvun muotojen herättäminen voidaan välttää laajalla taajuusalueella. Symmetrisesti syötetyillä antennirakenteilla saavutettu -6 dB suhteellinen impedanssikaistanleveys on 37.5–80 %. Useita syöttöelementtejä käytettäessä voidaan mobiilin laitteen maatasossa herättää yhdellä pistetaajuudella monta toisistaan riippumatonta säteilykenttää. Koska herätetyt kentät ovat toisistaan riippumattomia, on niiden välinen korrelaatio myös pieni. Kyseisellä rakenteella on mahdollista toteuttaa säteilykuviodiversiteetti erittäin pienessä tilassa, kuten matkapuhelimessa. Toisaalta, kun yhdistetään kaksi QCA-elementtiä yhdeksi monielementtiratkaisuksi, voidaan toteuttaa laajakaistainen diversiteettiantenni, jonka suhteellinen -6 dB impedanssikaistanleveys on 87.5 %. Vastaavasti kahdella laajakaistaisella QCA-elementillä toteutetulla MIMO-ratkaisulla päästään 95 % suhteelliseen -6 dB impedanssikaistanleveyteen. Molemmilla ratkaisuilla on erittäin hyvät säteilyominaisuudet sekä alhainen korrelaatio ja pieni keskinäiskytkentä antennielementtien välillä. Suunniteltaessa toimivaa laajakaistaista antennirakennetta, on tärkeää ottaa huomioon antennisyötön impedanssisovitus, jotta antennin suorituskyky ei heikkenisi. Lisäksi balansoidussa rakenteissa tulee olla laajakaistainen baluni, jolla vältetään säteilykuvion vääristyminen. Väitöskirjan syöttöratkaisuissa on käytetty kaupallisia sähkömagneettisia simulaattoreita, joilla antennirakenne voidaan mallintaa kolmiulotteisesti, ja joilla laajakaistainen syöttö saadaan optimoitua haluttuun antenniin. Suurin osa esitellyistä antennirakenteista on simulointien lisäksi myös mitattu, jolloin niiden toimivuus käytännössä pystytään todentamaan rakentamalla prototyyppiantenni. Yleisesti väitöskirjassa esitellään tasomaisia antenniratkaisuja johtavassa maatasossa, joissa säteilevät pintavirrat herätetään mahdollisimman laajalla taajuusalueella. Ideana on löytää laajakaistaisia antenni- ja syöttörakenteita, joilla saadaan herätettyä perusmuoto tai jokin muu haluttu muoto. Ajatuksena on välttää korkeamman kertaluvun muotojen herättäminen, jotka voivat pilata antennin suorituskyvyn. Väitöskirjassa osoitetaan myös, että pienikokoisella antennilla on mahdollista herättää korkeamman kertaluvun muotoja pistetaajuudella käyttämällä useita heräte-elementtejä
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3

Nikolayev, Denys. "Miniature antennas for biomedical applications." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S149.

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La télémétrie biomédicale et l’interfaçage neuronal à base de dispositifs miniatures et autonomes sans fil constituent de nouvelles applications en émergence. Elles visent à répondre à de nombreux enjeux y compris dans les domaines de la santé, du sport et bien être, ou encore de la sécurité au travail et de la défense. Parmi les applications typiques de biotélémétrie, nous pouvons citer le monitoring de certains paramètres physiologiques : température corporelle, pression artérielle, rythme cardiaque, taux de glucose et d’anticorps, détection d’agents chimiques, etc. En ce qui concerne l’interfaçage neuronal, il permet de restaurer les informations sensorielles, d’aider à la réadaptation des amputés, des personnes atteintes de paralysie ou des patients atteints de maladies neurodégénératives. L’objectif principal de cette thèse est de contribuer au développement de dispositifs miniaturisés et communicants pour le monitoring, en continu, de variables physiologiques d’humains ainsi que d’animaux. Ces dispositifs innovants nécessitent un système de communication fiable. Plus particulièrement, il s’agit d’analyser le milieu de propagation à l’intérieur des tissus biologiques et de développer des antennes miniatures innovantes ainsi que des méthodes pour leur analyse et leur caractérisation. Le verrou majeur concerne le rendement des antennes miniatures. Les effets de forte hétérogénéité, dispersion, pertes très élevées des milieux biologiques et les contraintes de miniaturisation et d’intégration dans des dispositifs in-body limitent la portée des systèmes existants à quelques dizaines de centimètres. Tout d’abord, des outils spécifiques de modélisation et d’optimisation ont été développés en collaboration avec l’Université de Bohème de l’Ouest. Ces outils sont indispensables pour l’analyse des composants de systèmes antennaires complexes : le code Agros2D (CAO interne) utilise des méthodes entièrement adaptatives. Cette approche permet de réduire la complexité d’optimisation des antennes in-body jusqu’un seul dégrée de liberté. Puis, la limite fondamentale de rendement des antennes pour les applications in-body a été définie ; les liens entre cette limite et la taille de l’antenne, sa fréquence de fonctionnement, la polarisation et les matériaux utilisés (dont hypothétiques) ont été quantifiés pour la première fois. Ce travail fondamental a d’abord pour objectif l’optimisation des performances de l’antenne actuelle de la capsule e-Celsius de l’entreprise BodyCAP pour accroître la portée de la gélule, en prenant en compte les caractéristiques des matériaux et le milieu de propagation que constituent les tissus biologiques. Dans cette étape on inclut également la fabrication des prototypes de gélules télémétriques ainsi que leurs mesures d’impédance. L’antenne optimisée a une portée trois fois plus importante que celle actuelle tout en occupant le même volume. En utilisant ces principes de conception, nous avons développé et caractérisé une antenne à 434 MHz adaptée à une large gamme d'applications in-body. Des dimensions ultra-miniatures, une robustesse et un rendement accrus permettent de l'utiliser à la fois pour des applications des capsules à implanter et à avaler. Enfin, en développant davantage les méthodes de conception et d’optimisation, nous avons conçu une antenne double-bande. Ayant la même robustesse que son équivalent actuel mono-bande, elle présente également un rendement encore plus élevé, permettant ainsi de fonctionner au-delà de 10 m. La caractéristique double-bande permet de concevoir les dispositifs in-body rechargeables sans fil dans le corps. Les antennes proposées contribuent au développement ultérieur d'une nouvelle génération de dispositifs miniatures in-body qui impliquent une intégration complexe et dense des capteurs, de la logique et de la source d'alimentation
Emerging wireless biotelemetry using miniature implantable, ingestible or injectable (in-body) devices allows continuously monitor and yield human or animal physiological parameters while maintaining mobility and quality of life. Recent advances in microelectromechanical systems and microfluidics—along with ongoing miniaturization of electronics—have empowered numerous innovations in biotelemetry devices, creating new applications in medicine, clinical research, wellness, and defense. Among the typical applications, I can mention, for example, the monitoring of physiological variables: body temperature, blood pressure, heart rate, detection of antibodies, chemical, or biological agents. Biotelemetry devices require a reliable communication system: robust, efficient, and versatile. Improving the transmission range of miniature in-body devices remains a major challenge: for the time being, they are able to operate only up to a few meters. Among the main issues to face are low radiation efficiencies (< 0.1%), antenna impedance detuning, and strong coupling to lossy and dispersive biological tissues. Thus, the main goal of the thesis is to conduct a multi-disciplinary study on development, optimization and characterization of antennas for in-body biotelemetry devices. After state-of-the-art and the context, I start with the development on both physical and numerical approaches to account for the effect of human tissues on the antenna. I propose the methodology to achieve given electromagnetic properties at a given frequency based on the full factorial experiment and surface response optimization. In addition, I describe the spherical physical phantom for the far-field characterization along with a combination of feed decoupling techniques. I proceed by reviewing the trough-body propagation mechanisms and deriving the optimal frequency for the in-body devices. I formulate the problem using four phantoms (homogeneous and heterogeneous) and perform full-wave analysis using an in-house hp-FEM code Agros 2D. Next, I study the existing antenna used by the BodyCap Company for its e-Celsius capsule and the ways on how to improve its operating range and robustness under strict integration and material constraints. The mechanisms of antenna–body coupling are analyzed and the found solution improves the antenna IEEE gain by 11 dBi (the operating range is at least tripled). The existing matching circuit and balun are optimized too for the given application reducing its size from eleven to seven discrete elements. In the following chapters, I continue studying the decoupling of antennas from a body using specific microstrip designs and dielectric loading via capsule shell. By applying the developed approaches, a high robustness and radiation efficiency can be achieved. At first, I develop a proof-of-concept antenna that demonstrates that the perfect matching (detuning immunity) is achievable for the operation within all human tissues. Based on these results, I develop a miniature and versatile biotelemetry platform: a 17 mm x 7 mm alumina capsule containing a conformal 434 MHz antenna. The antenna is well matched to 50 Ohm within the majority of human tissues and operates with an arbitrary device circuitry. Like this, one can use it ''as is,'' applying it for a wide range of in-body applications. Then, I develop a low profile conformal dual-band antenna operating in 434 MHz and 2.45 GHz bands. Such antenna can integrate both data transmission and wireless powering functionality increasing the available space inside an in-body device and increasing its scope of applications. Finally, I present the perspective developments including in-body sensing methodology. The obtained results contributes to further development of a new generation of miniature in-body devices that involve complex and dense integration of sensors, logic, and power sources
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4

Trinh, Le-Huy. "Antennes reconfigurables pour les applications mobiles et réseaux sans fil." Thesis, Nice, 2015. http://www.theses.fr/2015NICE4047/document.

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Au cours de ces dernières années, les technologies de télécommunication ont fait d'énormes progrès, notamment dans les communications mobiles et les réseaux de capteurs sans fil (WSN). Pour répondre à l’augmentation de la capacité de transmission et à l’amélioration de la qualité des canaux de communications mobiles, l’élargissement de la bande de fonctionnement est nécessaire par l'utilisation d'antennes reconfigurables en fréquence. En outre, dans les applications WSN, afin de réduire les collisions, d’augmenter la distance de communication et d'optimiser la consommation, l’utilisation d’antennes reconfigurables en directivité est une bonne solution. Dans ce cadre, nos travaux de recherche ont portés sur la conception de différentes structures antennaires reconfigurables. Dans un premier temps nous avons réalisés une antenne reconfigurable à base de nouveaux éléments actifs, les digitally tunable capacitors (DTC). Ces composants sont de très bons candidats en vue d’une intégration d'antennes pour des applications communications mobiles et WSN. Ensuite nous nous sommes attachés à concevoir des structures multibande, MIMO et reconfigurables en fréquence, permettant d’augmenter la bande de fréquence de fonctionnement du système de communication, d'optimiser l'efficacité et la qualité spectrale et d'améliorer la qualité de canal. Enfin, une autre voie a été explorée, l’utilisation d’antennes reconfigurables en directivité pour des applications de WSN. Les résultats de simulation et de mesure sont également présentés dans ce chapitre. Grâce à l'utilisation de ce type de structures, la performance des WSN a été optimisée
In recent years, telecommunication technologies have enormous progress, especially cellular communications and wireless sensor networks. To meet the demand of increasing transmission capacity, improving quality of cellular communication channels, expanding the operating band of the equipment is necessary. As passive antenna has reached the limit on increasing the operating band with the small size, the use of frequency reconfigurable antenna is a feasible solution. Besides, in the applications of WSN, to reduce collisions, increase communication distance and optimize consumption, directional reconfigurable antenna is a good proposal. In this thesis we present several reconfigurable antenna structures. Firstly, a new component is introduced; digitally tunable capacitor (DTC). Thanks to its advantages, such parts are good candidate to be integrated in the antenna for cellular communication and wireless sensor network applications. After, several antennas are introduced include multiband antenna, MIMO and frequency reconfigurable antenna, which can be used to extend the operating frequency band of the communication system, optimize spectral efficiency and quality improve channel quality. The structures of these antennas are introduced together with the results of simulation and measurement for the purpose of solving the challenges given in the future cellular communications systems. And then, the proposed approach to the design of reconfigurable directional antennas is presented. Several reconfigurable directional antennas, which are used in applications of WSN, are introduced. Thanks to the use of directional antennas reconfigurable, performance of WSN system will be optimized
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5

Kabalan, Aladdin. "Miniaturisation et modélisation d’antennes monopoles larges bandes utilisant des matériaux magnéto-diélectriques en bande VHF." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S041/document.

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Les avions comportent plusieurs systèmes de navigation et de communication nécessitent des antennes VHF large bande. Réduire la taille de ses antennes est un enjeu majeur tout en gardant des bonnes performances. Cette thèse propose des nouvelles configurations d'antennes à profil bas utilisant des nouveaux matériaux nanocomposites non conducteurs constitués de nanoparticules magnétiques développés au Lab-STICC. Un monopole planaire large bande a été développé et optimisé avec un taux de miniaturisation de 60% grâce à l'utilisation d'un matériau magnéto-diélectrique de forte perméabilité et faible pertes couvrant seulement 5% de sa surface. Les résultats expérimentaux, en presque parfait accord avec les simulations, montrent que le diagramme de rayonnement est omnidirectionnel et que la polarisation est verticale, avec un bon niveau du gain. L'antenne monopole planaire insérée dans un MMD des dimensions limitées avec des pertes a été modélisée par un nouveau circuit équivalent multi résonant. Ce circuit est développé à partir de l'impédance d'entrée de l'antenne et des caractéristiques du MMD, et validé par les simulations avec un parfait accord entre les résultats
Airplanes with multiple navigation and communication systems require broadband VHF antennas. Reduce the size of these antennas is a major challenge while keeping good performances. This thesis proposes new configurations of low profile antennas using new nanocomposite non-conductive materials consisting of magnetic nanoparticles developed at Lab-STICC. A broadband planar monopole has been developed and optimized with a 60% miniaturization rate thanks to the use of a high permeability and low loss magneto-dielectric material covering only 5% of its surface. The experimental results, in almost perfect agreement with the simulations, show that the radiation pattern is omnidirectional and that the polarization is vertical, with a good level of gain. The planar monopole antenna inserted in a MMD of limited dimensions with losses was modeled by a new multi-resonant equivalent circuit. This circuit is developed from the input impedance of the antenna and the characteristics of the MMD. and validated by the simulations with a perfect agreement between the results
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6

Shahpari, Morteza. "Fundamental Limitations of Small Antennas." Thesis, Griffith University, 2015. http://hdl.handle.net/10072/365747.

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The physical size and material properties of antennas are major limiting factors of the antennas performance. These limitations are usually manifested through parameters such as bandwidth, quality factor and efficiency. The presented research examines these fundamental limitations with specific focus on electrically small antennas, and a new bound for antenna efficiency is developed.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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7

Gorla, Hemachandra Reddy reddy. "MINIATUIRIZED ULTRA-WIDEBAND ANTENNAS FOR WIRELESS COMMUNICATIONS." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/dissertations/1905.

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Wireless communication is part of our daily life in several applications, such as cell phones, wireless printers, sensors, etc. Each wireless device requires at least one antenna to communicate with other devices. In 2002, Federal Communications Commission (FCC) assigned a frequency spectrum from 3.1 GHz to 10.6 GHz for ultra-wideband communications. Several narrowband antennas require to cover the entire range. Unlike narrowband antennas, ultra-wideband antennas need to cover the wide frequency band. This research mainly focuses on physically small antenna designs. The first antenna discussed in this dissertation is a dual, triple trident antenna with dimensions 24 mm × 28 mm × 0.785 mm, which will operate from 3 GHz to 12.15 GHz [58]. The first antenna consists of six tridents symmetrical along the vertical direction. The second antenna design is a novel rectangular ring ultra-wideband antenna [59]. Large antennas operate for low frequency, and small antennas work for high frequency. The number of rings increased in wideband antenna to 9 from 4 to check the design methodology. The rectangular ring ultra-wideband antenna has dimensions 24 mm × 26 mm × 1.52 mm. This antenna operates from 3.12 GHz to 12.85 GHz. The third antenna design is an ultra-wideband dual square trident planar antenna. This antenna’s overall size is 26 mm × 24 mm × 1.56 mm [60]. This antenna has impedance bandwidth from 3.65 GHz to 12.50 GHz. The fourth antenna design is an ultra-wideband antenna with a band notch from 5.05 GHz to 5.9 GHz [61]. This antenna consists of two tridents and two split-ring resonators along the microstrip feed line. The overall size of this antenna 26 mm ×24 mm × 1.53mm. Simulations are carried out using the CST microwave studios® to analyze the antenna performance. Experiments are conducted to verify the simulated results using vector network analyzers for impedance and anechoic antenna chamber for radiation characteristics of the antenna. All four antennas are excellent for the wireless device due to their compact size and planar designs.
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8

Sousa, Jonas Rodrigo da Silva. "Estudo de antenas para comunicação na faixa de subterahertz." Universidade Federal Rural do Semi-Árido, 2016. http://bdtd.ufersa.edu.br:80/tede/handle/tede/766.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The antennas in nano-metric scales are part of a line of research that has been gaining strength in recent years, being the target of numerous studies and publications in several universities in Brazil and around the world. Nano antennas are characterized as a promising new branch in the development of devices capable of being applied in different areas, in addition to communication. Occupying a prominent place in the new era of technologies, the nano antennas, here restricted only to dipole and microstrip, generate enormous expectations about this new revolution, not only between researchers, but also in a part of society. Currently, wireless communications require that radiator devices have wide bandwidth and miniaturization for mobile devices, so this dissertation discusses the potential application of antennas for communications in the frequency range in Terahertz. At these frequencies, there are numerous restrictions on the propagation of signals, so high performance antenna are necessary to allow communication with reduced losses. The purpose of this work is to study some configurations and types of antennas, such as microstrip antenna and dipole antenna, with application in the subterahertz frequency, which can be used, for example, in internal networks, medicine, photovoltaic power generation, spectroscopy, near-field microscopy and high quality images. Some configurations of antennas with various materials for communications in the frequency range will be presented to verify the feasibility of the use of nano dipole antennas and miniaturized microstrip antennas in this type of application. The methodology adopted suggests the comparison of the simulated results, through the software Ansoft HFSS ® and CST Microwave Studio ®, with the results of other published works
As antenas em escalas nanométrica fazem parte de uma linha de pesquisa que vem aumentando nos últimos anos, sendo alvo de inúmeros estudos e publicações. As nanoantenas caracterizam-se como um novo e promissor ramo no desenvolvimento de dispositivos capazes de ser aplicados em diferentes áreas, além da comunicação. Ocupando lugar de destaque na nova era das tecnologias, as nanoantenas, aqui restritas somente as de dipolo e microfita, geram enorme expectativas. Atualmente as comunicações sem fio requer que os dispositivos radiadores possuam uma ampla largura de banda e miniaturização para dispositivos móveis, assim, essa dissertação discute a aplicação potencial de antenas para comunicações na faixa de frequência em Terahertz. Nessas frequências existem inúmeras restrições na propagação de sinais, então antenas com alto rendimento são necessárias para permitir comunicação com perdas reduzidas. A proposta desse trabalho é estudar algumas configurações e tipos de antenas, tais como de antena de microfita e antena dipolo, com aplicação na faixa de frequência em subterahertz, que podem ser utilizadas, por exemplo, nas redes internas, medicina, na geração de energia fotovoltaica, espectroscopia, microscopia de campo próximo e obtenção de imagens de alta qualidade. Serão apresentadas algumas configurações de antenas e com diversos materiais para comunicações na faixa de frequência em questão, para verificar a viabilidade do uso de nanoantenas de dipolo e de antenas de microfita miniaturizadas neste tipo de aplicação. A metodologia adotada sugere a comparação dos resultados simulados, através dos softwares Ansoft HFSS ® e CST Microwave Studio ®, com os resultados de outros trabalhos publicados
2017-07-14
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9

Martinis, Mario. "Développement et caractérisation de métamatériaux pour application en cavité : application à la conception d'antennes compactes." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S107/document.

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Cette thèse présente de nouveaux développements pour de petites antennes en cavité. L'objectif principal de la thèse est l'analyse de la performance de la bande passante de ces antennes pour des tailles d'ouverture qui sont petites par rapport à la longueur d'onde en espace libre. Des cavités de formes rectangulaires et circulaires intégrées dans un plan de masse infini et dans des plans de masse de dimensions latérales finies sont examinées en détail. Jusqu'à présent, dans la littérature, le choix pour ces antennes en cavités portait sur des antennes imprimées microruban (patch). L'objet de la thèse est de déterminer si les performances d'antennes en cavité de petite taille peuvent être améliorées et si oui, de quelle façon. A cet effet, nous avons tout d'abord étudié théoriquement, la limite supérieure de la bande passante pour cette configuration particulière en cavité. Nous en avons conclu que les antennes microruban intégrées dans une cavité n'atteignent pas la limite de la bande passante, ce qui est l'un des principaux résultats de la thèse. Les antennes intégrées dans une cavité avec un plan de masse infini ou fini sont ensuite analysées à l'aide de plusieurs modèles de ligne de transmission simples. Le deuxième résultat clé de la thèse un modèle de ligne de transmission spécifique et original qui montre que cette limite sur la bande passante est réellement atteignable. Par conséquent, ce modèle de ligne de transmission devient la base d'une nouvelle conception pour l'antenne en cavité. Enfin, le résultat le plus important de la thèse est la conception concrète de nouvelles antennes en cavité capables d'atteindre la performance maximale en bande passante. D'autres sujets sont abordés sont: i) la comparaison avec des structures à base d'éléments empilés en termes de bande passante, de facilité de fabrication et de coût, ii) l'extension de la limite grâce à l'inclusion de matériaux magnétiques idéaux et conducteurs magnétiques; iii) l'utilisation de la nouvelle structure d'antenne pour la constitution d'un réseau d'antennes compact; iv) les avantages de la nouvelle structure pour la réalisation d'antennes en cavité de tailles vraiment petites pour lesquelles les méthodes classiques ne permettent pas la réalisation d'antennes
This thesis presents new developments in cavity type antennas. The main objective of the thesis is bandwidth performance analysis of antennas in cavities with aperture sizes which are small compared to the free space wavelength. Cavities of rectangular and circular shapes in an infinite and finite ground plane are investigated in detail. So far in the literature, microstrip patch antennas were the antenna of choice for cavity type antennas. The intention of the thesis is to determine if cavity type antennas can be improved and how. To this end, the bound on bandwidth for cavity antennas is investigated theoretically. It is concluded that patch antennas, in fact, do not reach the bound for cavity antennas, which is one of the key results of the thesis. Infinite and finite sized ground plane cavity antennas are further analyzed using several simple transmission line models. The second key result of the thesis is a demonstration that a special transmission line model corresponds to antennas that reach the bound on bandwidth. This transmission line model is the basis to a new cavity antenna design. Finally, the most important result is a practical, physical, design of novel cavity antennas capable of reaching the bandwidth bound. Furthermore, several additional topics are explored; i) A comparison with stacked patches design in terms of bandwidth, ease of fabrication, and cost; ii) The extension of the bound with the inclusion of ideal magnetic materials and magnetic conductors; iii) The new antenna design use in constructing a compact antenna array; iv) The benefits of the new design for constructing small cavity antennas previously not feasible with the classical design
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10

Li, Hui. "Decoupling and Evaluation of Multiple Antenna Systems in Compact MIMO Terminals." Doctoral thesis, KTH, Elektroteknisk teori och konstruktion, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-96239.

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Research on multiple antenna systems has been a hot topic in recent years due to the demands for higher transmission rate and more reliable link in rich scattering environment in wireless communications. Using multiple antennas at both the transmitter side and the receiver side increases the channel capacity without additional frequency spectrum and transmitted power. However, due to the limited space at the size-limited terminal devices, the most critical problem in designing multiple antennas is the severe mutual coupling among them. The aim of this thesis is to provide compact, decoupled and efficient multiple antenna designs for terminal devices. At the same time, we propose a simple and cost effective method in multiple antenna measurement. All these efforts contribute to the development of terminal devices for the fourth generation wireless communication. The background and theory of multiple antenna systems are introduced first, in which three operating schemes of multiple antenna systems are discussed. Critical factors influencing the performance of multiple antenna systems are also analyzed in details. To design efficient multiple antenna systems in compact terminals, several decoupling methods, including defected ground plane, current localization, orthogonal polarization and decoupling networks, are proposed. The working mechanism and design procedure of each method are introduced, and their effectiveness is compared. Those methods can be applied to most of the terminal antennas, reducing the mutual coupling by at least 6dB. In some special cases, especially for low frequency bands below 1GHz, the chassis of the device itself radiates like an antenna, which complicates the antenna decoupling. Thus, we extend the general decoupling methods to the cases when the chassis is excited. Based on the characteristic mode analysis, three different solutions are provided, i.e., optimizing antenna locations, localizing antenna currents and creating orthogonal modes. These methods are applied to mobile phones, providing a more reliable link and a higher transmission rate, which are evaluated by diversity gain and channel capacity, respectively. In order to measure the performance of multiple antenna systems, it is necessary to obtain the correlation coefficients. However, the traditional measurement technique, which requires the phase and polarization information of the radiation patterns, is very expensive and time consuming. In this thesis, a more practical and convenient method is proposed. Fairly good accuracy is achieved when it is applied to various kinds of antennas. To design a compact and efficient multiple antenna system, besides the reduction of mutual coupling, the performance of each single antenna is also important. The techniques for antenna reconfiguration are demonstrated. Frequency and pattern reconfigurable antennas are constructed, providing more flexibility to multiple antenna systems.
QC 20120604
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11

Chiu, Chi Yuk. "Impedance bandwidth broadening techniques for small patch antennas /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ee-b19887796a.pdf.

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Thesis (Ph.D.)--City University of Hong Kong, 2005.
"Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references (leaves 152-162)
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12

Duran, Venegas Juan Antonio. "Reconfigurable Metasurfaces for Beam Scanning Planar Antennas." Thesis, Toulouse, INPT, 2016. http://www.theses.fr/2016INPT0102.

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Nous étudions la mise en oeuvre d ‘antenne à balayage électronique dédiés aux applications de communications par satellite géostationnaire. Les structures développées sont adaptées pour être embarquées dans un avion ou un train. L'architecture de l'antenne développée est constituée d’un double réseau linéaire dans deux dimmensions transverses. Le balayage dans chaque réseau linéaire est assuré par des lignes coplanaires à métamateriaux contrôlées par varactor. Nous porposons de nouvelles méthodes de caracterisation des discontinuités en ligne coplanaire pour la conception de la ligne. De plus, un système de prélèvement d'énergie a dû être conçu afin d'alimenter des éléments rayonnants et testé avec différentes antennes patch. Enfin, nous envisageons la co-intégration des structures rayonnantes et des lignes CRLH ainsi que le contrôle électronique par les diodes
We are studying the implementation of 'Scanning Antenna dedicated to the applications of satellite communications geostationary. The structures developed are suitable for to be on board an airplane or a train. The architecture of the antenna developed consists of a double linear network in two transverse dimmensions. The scan in each network is provided by the lines coplanar to metamaterials controlled by varactor. We porposons of new methods characterization of discontinuities coplanar online for the line design. In addition, a energy harvesting system has be designed to feed radiating elements and tested with patch different antennas. Finally, we are considering co-integration radiating structures and CRLH lines as well as control electronic by the diodes
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13

Jaeck, Vincent. "Développement d’antennes de communication reconfigurables en bande C pour munitions intelligentes." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S104/document.

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De nos jours, les communications sans fil sont devenues un moyen incontournable et universel d'échange d'un large éventail d'informations entre différents systèmes, certains d'entre eux étant en mouvement comme des drones parmi tant d'autres. Dans le contexte de cette thèse nous considérons une liaison entre un projectile et une station de base. La géométrie de la structure ainsi que les contraintes aérodynamiques d'un tir balistique impliquent l'utilisation d'antennes patchs dans la partie conique à l'avant du projectile. Ce type d'antenne est facile à intégrer à une plate-forme en tant que réseau conformé tout en respectant les contraintes d'encombrement. Ces communications doivent être fiables et discrètes dans un environnement perturbé ou hostile. Les diagrammes de rayonnement du réseau d'antennes doivent présenter des caractéristiques spécifiques, notamment dans le cas particulier d'objets volants et possédant une rotation en roulis (rotation autour de son axe) qui impliquent l'utilisation d'un réseau phasé et commuté par rapport à sa position. Une antenne qui présenterait un rayonnement fixe assurerait une liaison avec un interlocuteur, mais rayonnerait également dans d'autres directions sensibles ce qui pourraient interférer avec la communication principale. La solution qui consiste à activer et désactiver des sous-réseaux verticaux afin d'orienter le lobe principal dans la plan orthogonal à la pointe semble être en accord avec les contraintes de la structure tournante. Un réseau conique a été étudié puis 2 prototypes ont été fabriqués, dont un à l'ISL. Les sous-réseaux sont répartis de manière égale autour de la pointe de façon à pouvoir rayonner dans toutes les directions. De plus, chaque sous-réseau est composé de trois éléments ce qui permet d'orienter également le lobe principal dans le plan longitudinal de la pointe (le long de l'axe du projectile) grâce à un dépointage électronique. Un système électronique de formation de faisceaux a été développé dans le but de contrôler 12 éléments rayonnants. Le réseau d'antennes ainsi que le circuit de répartition ont été caractérisés dans un premier temps de manière indépendante afin d'optimiser les lois de phase nécessaires à dépointer le lobe à partir des pondérations mesurées. Au final, le réseau de 12 éléments associé à son système d'alimentation dédié a été mesuré dans les chambres anéchoïques de DGA-MI et de l'ISL et les mesures sont en accord avec les simulations
Nowadays wireless communications have become a useful and universal mean to exchange a wide range of information between different systems, some of them being moving, as UAVs among others. In this context we consider here the link between a projectile and a base station. The shape of the structure and the aerodynamic constraints involve the use of patch antennas in the conical front part. This class of antenna is easy to be integrated into the platform as a conformal array, while respecting space constraint. Communications have to be reliable and discrete in disturbed or hostile environment. Antennas array radiation patterns must have some specific characteristics, in particular in the case of flying objects with spin which involves the use of a switched phased array considering its roll position. A fixed-radiation pattern antenna may presents a relevant level or gain toward the interlocutor, but also toward sensitive directions, in which may be located others systems, interfering with the current communication. The solution to switch on and off vertical sub-arrays to steer the beam in the azimuthal plane seem convenient ant fitting the requirements of rotating platform. A conical phased array was studied and two prototypes were manufactured, one at ISL. Sub-arrays are distributed around the conical shape in order to be able to radiate in each direction. Moreover, each sub-array are composed of three radiating elements allowing to steer the main antenna beam in many direction (along the projectile fuze axes). A beam forming network was developed to control the 12 radiating elements conical array. The antenna array and the feeding network were characterized independently in order to optimized the phase of each radiating element. Finally, measurements were done on the whole system in the DGA-MI and ISL anechoic chambers and are in good agreement with simulation results
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14

Weeratumanoon, Eakasit. "Helical Antennas with Truncated Spherical Geometry." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/31193.

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A new variation of the spherical helical antenna made of a wire wound over a hemispherical surface and backed by a conducting ground plane is introduced. A constant spacing is maintained between the turns of winding. The geometry of this antenna is fully described by the number of turns and the radius of hemispherical surface. In addition to the hemispherical geometry, truncated double spherical helices are also examined. Radiation properties of the proposed antennas are studied both theoretically and experimentally. The wire antenna code ESP (electromagnetic surface patch), which is based on the method of moments, is used to obtain simulation results. The results for far-field patterns, gain, axial ratio, bandwidth, and input impedance are presented. Several prototypes of this antenna were constructed and tested using an outdoor antenna range. Far-field patterns were measured over a wide range of frequencies. The measured and calculated radiation patterns are in good agreement.

A unique property of the hemispherical helix is its broad half-power beamwidth. Furthermore, this antenna provides circular polarization and relatively high gain over a narrow frequency range. The results of this research show that, for example, a 4.5-turn hemispherical helix with a radius of 0.02 meter designed for operation around 2.8 GHz provides a half-power beamwidth of about 90 degrees, more than 9 dB gain, and less than 3 dB axial ratio over a 300 MHz bandwidth. The input impedance of the antenna is largely resistive and is about 150 ohms in the above frequency range. Compared with a full spherical helix, the hemispherical helix provides comparable radiation characteristics, but occupies only half the volume. The compact size of this antenna makes it attractive to mobile communication applications
Master of Science

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15

Scattone, Francesco. "Phased array antenna with significant reduction of active controls." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S168/document.

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L'objectif de cette thèse est d'exploiter les phénomènes des ondes de fuite pour améliorer les performances des antennes classiques à ouverture pour les applications spatiales. Ici, nous considérons des configurations planaires où les ondes de fuite sont excitées entre un plan de masse et un superstrat partiellement réfléchissant. Des réseaux de petites ouvertures sur le plan de masse sont utilisés pour alimenter les antennes considérées. Les structures avec superstrat sont développées en configuration réseaux simples ou réseaux à commande de phase, considérées intéressantes en termes de flexibilité du système pour des liens satellitaires de nouvelle génération.Pour étudier efficacement ces antennes, nous avons développé un outil d'analyse basé sur une approche spectrale avec fonction de Green. Cet outil permet d'analyser les structures proposées en prenant en compte l'impact du couplage mutuel entre les éléments sur les performances de rayonnement avec une réduction du temps de calcul et d'utilisation de mémoire.L'augmentation du gain des structures à ondes de fuite peut ouvrir la voie à la réduction du nombre d'éléments des réseaux associés, et donc des commandes en amplitude et phase. Dans une configuration à ondes de fuite, chaque élément du réseau rayonne avec une ouverture équivalente plus grande, augmentant ainsi l'espacement entre les éléments sans affecter le gain global de la structure. Comme largement expliqué dans le manuscrit, les solutions à ondes de fuite représentent par conséquent un avantage majeur pour les antennes du segment utilisateur.En plus de l'amélioration du gain, la technologie à ondes de fuite peut être efficacement exploitée pour synthétiser le diagramme de rayonnement, en choisissant correctement les paramètres de conception de l'antenne. Cette caractéristique peut être utilisée dans les réseaux à commande de phase, pour produire un diagramme d'élément qui minimise les pertes par dépointage et qui filtre les lobes de réseaux. Une procédure de synthèse pour des antennes réseaux raréfiés à ondes de fuite est ainsi présentée dans le manuscrit, ainsi qu'une nouvelle configuration de réseaux avec superstrat irrégulier. Ce dernier permet de réduire les lobes secondaires de l'antenne en utilisant une excitation uniforme. Cette dernière configuration montre clairement que la capacité de modifier le diagramme de rayonnement est la caractéristique la plus attrayante des antennes planaires à ondes de fuite, pour être utilisée dans des solutions de réseaux à commande de phase
The objective of this thesis is to exploit the leaky-wave phenomena to enhance the performance of classical aperture antennas for space applications. Here, we consider planar configurations where the leaky modes are excited between a ground plane and a partially reflective superstrate. Arrangements of small apertures opening on the ground plane are used to feed the antennas under study. The superstrate-like leaky-wave structures are developed in array or phased array configurations, considered of interest in terms of flexibility of the system for next generation satellite links. In order to efficiently study planar leaky-wave arrays, we have developed an analysis tool based on a Green's function spectral approach. The developed tool allows to precisely analyze the proposed structure by taking into account the impact of the mutual coupling among the elements on the radiation performance of the whole antenna. In addition, it can handle extremely large structures in terms of wavelengths with a small computational effort with respect to commercial tools. In particular, the gain enhancement of leaky-based structures can pave the way to the reduction of the number of elements of the associated phased arrays. In a leaky-wave configuration each element of the array will radiate with a larger equivalent aperture allowing a larger spacing among elements without affecting the final gain of the whole structure. This aspect is particularly important in the case of phased arrays, where phase shifters and control cells are, typically, the most expensive components of the system. As extensively explained in the manuscript, antennas for user segment might find the highest benefit by using leaky-wave solutions. Besides the gain enhancement, the leaky-wave technology can be effectively exploited to conveniently shape the radiation pattern by properly engineering the design parameters of the antenna. This capability can be used in phased arrays to generate a convenient element pattern to minimize the scan losses and filter the grating lobes appearing in the visible space when dealing with periodicities larger than a wavelength. Therefore, a synthesis procedure for thinned leaky-wave arrays is presented in the manuscript. Also, a novel array configuration, the irregular superstrate array, is presented. The irregular superstrate allows the reduction of the side lobes of the antenna below -20 dB in the considered 2.5 % band, using a uniform excitation. This last configuration clearly shows that the shaping capability of leaky-wave antennas is the most appealing feature to be used in phased array solutions
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16

Perotoni, Marcelo Bender. "Projeto e desenvolvimento de lentes discretas." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-25072005-081712/.

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O presente trabalho trata do estudo, projeto, desenvolvimento, construção e medida de lentes discretas planares (DLAs). Estes dispositivos atuam como sistemas irradiantes, especialmente com características multi-feixes. A construção destas lentes utiliza tecnologias compatíveis com a fabricação de circuitos impressos, com alguns detalhes que são característicos da área de antenas e circuitos planares. O estudo aborda as equações de projeto e considerações gerais relativas ao atendimento de especificações técnicas preliminares. Foram desenvolvidas duas lentes discretas, uma na frequência de 8GHz (banda X) e outra na frequência de 40GHz (banda Ka- faixa de ondas milimétricas). São apresentados os resultados de medidas destas duas lentes, que comprovam a possibilidade de uso em aplicações multi-feixes, bem como seu efeito de foco, análogo ao observado em lentes óticas comuns.
The object of this work is the study, design, development, fabrication and measurement of discrete lens arrays (DLAs). These devices act as radiant systems, especially with multi-beam characteristics. Their construction follows the same procedures and techniques normally found in printed circuit fabrication, with some further details that are pertinent to the antenna and planar circuit field. This study contains the design equations and general remarks as to fulfill preliminary technical specifications. Two real designs were developed, one in the X-band (8GHz) and another in the millimeter range, Ka band (40GHz). Their respective measurement results are presented, which proved their possible application in multi-beam systems, as well as their focusing effect, which is analogous to that observed in common optical lenses.
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17

Hwang, Seung-Hyeon. "Adaptive antenna techniques for smart antennas and radar systems." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2005. http://wwwlib.umi.com/cr/syr/main.

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18

Alsawaha, Hamad Waled. "New Designs for Wideband Hemispherical Helical Antennas." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/34285.

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A unique property of spherical and hemispherical helical antennas is that they provide very broad half-power beamwdiths and circular polarization over a narrow bandwidth. In this thesis, new designs for hemispherical helical antennas are introduced that provide significant improvement in bandwidth, while maintaining the directivity and half-power beamwidth of the basic design. In the basic design, a simple wire of circular cross section is wound on the surface of a hemisphere, whereas in the proposed new designs a metallic strip forms the radiating element. Furthermore, the metallic strip may be tapered and tilted relative to the hemispherical surface, allowing wider bandwidth to be achieved. The antenna is fed by a coaxial cable with the inner conductor connected, through a matching section, to the radiating strip and its outer conductor connected to a ground plane.

Radiation properties of the proposed hemispherical helical antennas are studied both theoretically and experimentally. A commercial software, based on the method of moments, is used to perform the numerical analysis of these helices. Three-dimensional far-field patterns, axial ratio, directivity, and voltage standing-wave ratio (VSWR) are calculated for several designs. The impacts of tapering as well as tilting of the metallic strip on radiation characteristics are examined. Also, matching of the proposed hemispherical antennas to 50⠦ transmission lines is addressed. A 4.5-turn hemispherical helix with tapered radiating element and zero degree tilt angle, (metallic strip is perpendicular to the hemisphere axis of symmetry) provides the largest overall bandwidth. A nonlinearly tapered matching section is incorporated into the design in order to reduce the VSWR. For this design, an overall measured bandwidth of about 24% at a center frequency of 3.35 GHz is achieved. Over this bandwidth, the axial ratio remains below 3 dB, the VSWR is less than 2, and the directivity is about 9 ±1 dB. A half- power beamwidth of 70° is also obtained.

A prototype of the best design was fabricated and tested using the VT indoor antenna range. Radiation patterns, the scattering parameter S11, and the axial ratio were measured. The measured and simulated results agree reasonably well. In particular, agreements between measured and calculated far-field patterns and VSWR are quite remarkable. This compact, low profile antenna might find useful applications in avionics, global positioning systems (GPS), and high data rate wireless communication systems.
Master of Science

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19

Öjefors, Erik. "Integrated Antennas : Monolithic and Hybrid Approaches." Doctoral thesis, Uppsala University, Department of Engineering Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7142.

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This thesis considers integration of antennas and active electronics manufactured on the same substrate. The main topic is on-chip antennas for commercial silicon processes, but hybrid integration using printed circuit board technology is also addressed.

The possible use of micromachining techniques as a means of reducing substrate losses of antennas manufactured on low resistivity silicon wafers is investigated. Compact dipole, loop, and inverted-F antennas for the 20-40 GHz frequency range are designed, implemented, and characterized. The results show significantly improved antenna efficiency when micromachining is used as a post-processing step for on-chip antennas manufactured in silicon technology.

High resistivity wafers are used in a commercial silicon germanium technology to improve the efficiency of dipole antennas realized using the available circuit metal layers in the process. Monolithically integrated 24 GHz receivers with on-chip antennas are designed and evaluated with regard to antenna and system performance. No noticeable degradation of the receiver performance caused by cross talk between the antenna and the integrated circuit is observed.

For low frequency antenna arrays, such as base station antennas, hybrid integration of active devices within the antenna aperture is treated. A compact varactor based phase shifter for traveling wave antenna applications is proposed and evaluated. Electrically steerable traveling wave patch antenna arrays, with the phase shifters implemented in the same conductor layer as the radiating elements, are designed and manufactured in microstrip technology. It is experimentally verified that the radiation from the feed network and phase shifters in the proposed antenna configuration is small.

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20

Ribeiro, Daniel Luiz. "Utilização de antena fractal de microfita em projetos de estruturas eletricamente pequenas e independentes da frequência." Universidade Federal de Uberlândia, 2016. https://repositorio.ufu.br/handle/123456789/17937.

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Antenas fractais são estruturas irradiadoras geradas recursivamente a partir da aplicação reiterada de um fator de conjunto gerador, possuindo a característica marcante de ser auto semelhante. São baseadas na teoria dos fractais desenvolvida por Mandelbrot e cuja aplicação se encontra presente em quase todos os ramos da ciência. Tais antenas possuem hoje inúmeras aplicações, de celulares a antenas de satélites, e têm se mostrado uma alternativa atraente para aplicações que requeiram característica de multibanda associada a alto ganho e miniaturização. O presente trabalho procura apresentar de forma sistemática a teoria básica envolvendo antenas fractais, tendo-se por base não apenas as contribuições pioneiras de pesquisadores no mundo todo, mas também a teoria básica de antenas, a partir das quais é possível chegar-se a formulações importantes na área. O foco é para antenas de microfita, dada a grande popularidade que têm encontrado nas últimas décadas. Além de vasta bibliografia, contou-se com o auxílio da ferramenta computacional HFSS da Ansoft®, um software que simula estruturas em alta frequência. Este programa é utilizado para simular uma antena fractal de microfita proposta pelo autor, e os resultados são analisados tendo-se um duplo propósito: exemplificar o uso de uma antena fractal, por um lado, e fornecer um protótipo que porventura poderá ser utilizado em aplicações especiais, por algum projetista de antenas. Os principais parâmetros fundamentais de antenas são analisados, como Perda de Retorno, VSWR, Ganho, etc., mas será dada ênfase especial à aplicação de estruturas fractais de microfita em dois tipos de aplicações: antenas eletricamente pequenas e antenas independentes da frequência.
Fractal Antennas are radiating structures generated recursively from the reiterated application of a generating array, having the remarkable feature of being self similar. They are based on the theory of fractal developed by Mandelbrot and whose application is present in almost every branches of science. Such antennas have many applications today, from cell phones to satellite antennas, and have proved to be an attractive alternative for applications that required multiband characteristic associated with high gain and miniaturization. This paper aims do present systematically the basic theory involving fractal antennas, and is based not only on the pioneering contributions of researchers around the world, but also the basic theory of antennas, from which is possible to reach important formulations in the area. Besides the extensive bibliography, was used the computational tool HFSS by Ansoft®, a software that simulates high frequency structures. This program is used to simulate a fractal microstrip antenna proposed by the author, and the results are analyzed, having a dual propose: to exemplify the use of fractal antenna on the one hand, and providing a prototype which could possible be used in special applications, for some designer of antennas. The main fundamental parameters of antennas are analyzed, such as Return Loss, VSWR, Gain, etc., but special emphasis will be given to the application of fractal microstrip structures in two kinds of applications: electrically small antennas and frequency independent antennas.
Dissertação (Mestrado)
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21

Li, Pei. "Novel wideband dual-frequency L-probe fed patch antenna and array /." access abstract and table of contents access full-text, 2006. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ee-b21471447a.pdf.

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Thesis (Ph.D.)--City University of Hong Kong, 2006.
"Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references (leaves 179-189)
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22

Freitas, Renata Valerio de. "Análise de antenas no domínio do tempo." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-19112012-114901/.

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As recentes aplicações que utilizam bandas ultralargas e comunicação pulsada necessitam de antenas adaptadas às suas necessidades. Para tanto, é necessário entender melhor o funcionamento dessas antenas em toda a banda utilizada e sua resposta aos pulsos de entrada. Nesse sentido, algumas ferramentas de análise de antenas no domínio do tempo foram desenvolvidas e utilizadas de modo a explicar o mecanismo de radiação de algumas antenas. Através da utilização de estruturas grandes com relação à duração do pulso de entrada, é possível identificar como o pulso se propaga e é refletido pela estrutura. Em seguida, é estabelecida a relação entre a localização do pulso e a radiação gerada pela geometria da antena nessa posição. Com isso se pode identificar as origem das características da resposta impulsiva da antena e a sua relação com a aceleração de cargas que ocorre na estrutura. Finalmente, são apresentados alguns resultados relacionados ao desempenho da antena como dispersão, distorção e diagrama de radiação de energia normalizado.
The recent applications that uses UWB and pulse communications demands antennas that fits better its constraints. Therefore, it is necessary to understand the behaviour of these antennas in all the bandwidth used and its response to input pulses. With this objective, some analysis tools for antennas in the time domain have been developed. These tools provided and explanation to the radiation mechanism of some antennas. Through the use of large structures with respect to the duration of the input pulse it is possible to identify how the pulse propagates and how it is reflected by the structure. The relationship between the pulse position and the radiation of the antenna is then established for every position. This procedure enables the identification of the relationship between the antenna impulse response and the acceleration of charges in the structure. Finally, we present some results related to the performance of the antenna such as dispersion, distortion and normalized energy radiation pattern.
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23

Hildebrand, Louis Trichardt. "The analysis of microstrip wire-grid antenna arrays." Pretoria : [s.n.], 2010. http://upetd.up.ac.za/thesis/available/etd-01272010-130234/.

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24

Ong, Chin Siang. "Digital phased array architectures for radar and communications based on off-the-shelf wireless technologies." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FOng.pdf.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2004.
Thesis advisor(s): David C. Jenn, Siew Yam Yeo. Includes bibliographical references (p. 63-64). Also available online.
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25

Sundaram, Ananth Ramadoss Ramesh. "Electronically Steerable Antenna Array using PCB-based MEMS Phase Shifters." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Theses/SUNDARAM_ANANTH_51.pdf.

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26

Davids, Vernon Pete. "Implementation of a wideband microstrip phased array antenna for X-band radar applications." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1100.

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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009
This thesis presents the design, analysis and implementation of an eight-element phased array antenna for wideband X-band applications. The microstrip phased array antenna is designed using eight quasi-Yagi antennas in a linear configuration and is printed on RT/Duroid 6010LM substrate made by Rogers Corporation. The feeding network entails a uniform beamforming network as well as a non-uniform -25 dB Dolph-Tschebyscheff beamforming network, each with and without 45° delay lines, generating a squinted beam 14° from boresight. Antenna parameters such as gain, radiation patterns and impedance bandwidth (BW) are investigated in the single element as well as the array environment. Mutual coupling between the elements in the array is also predicted. The quasi-Yagi radiator employed as radiating element in the array measured an exceptional impedance bandwidth (BW) of 50% for a S11 < -10 dB from 6 GHz to 14 GHz, with 3 dB to 5 dB of absolute gain in the frequency range from 8 GHz to 11.5 GHz. The uniform broadside array measured an impedance BW of 20% over the frequency band and a gain between 9 dB to 11 dB, whereas the non-uniform broadside array measured a gain of 9 dB to 11 dB and an impedance BW of 14.5%. Radiation patterns are stable across the X-band. Beam scanning is illustrated in the E-plane for the uniform array as well as for the non-uniform array.
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27

Jaafar, Hussein. "Antennes miniatures, large bande et superdirectives à charges optimisées par l'analyse des modes caractéristiques." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S031/document.

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L'évolution rapide dans les systèmes de communication sans fil nécessite plus de miniaturisation de divers composants électroniques en plus de l'élément majeur de la technologie sans fil : l'antenne. Dans ce cas, une antenne occupant un espace limité devrait être miniaturisée pour fonctionner aux bandes de communication souhaitées. Cependant, à mesure que la taille électrique de l'antenne diminue, ses performances se dégradent considérablement et sa bande passante, son efficacité et sa directivité sont limitées. Les techniques classiques de réduction de la taille avec chargement de matériau et mise en forme géométrique de l'antenne souffrent d'une bande passante étroite et d'une faible efficacité de rayonnement. D'autre part, les tentatives d'augmenter la directivité des petites antennes en utilisant des réseaux superdirectifs sont également associées à une faible efficacité de rayonnement bande passante très étroite. Pour pallier ces inconvénients, nous proposons de booster les performances des antennes compactes en utilisant des charges réactives embarquées. En plaçant correctement les charges (actives ou passives) à l'intérieur de l'antenne, il est possible de contrôler les courants pour améliorer de manière significative les performances de l'antenne en termes de bande passante et de directivité. Cependant, pour un succès des critères de chargement, il est obligatoire d'analyser les modes naturellement supportés par l'antenne étudiée. On les appelle les modes caractéristiques, qui fournissent des aperçus physiques profonds sur le comportement de l'antenne et ses modes de rayonnement. En combinant cette théorie avec l'algorithme d'optimisation, il devient possible de manipuler de manière optimale les courants à l'intérieur de l'antenne en utilisant des charges réactives pour obtenir des conceptions large bande, superdirectives et efficaces
The rapid evolution in the wireless communication systems requires more miniaturization of various electronic components in addition to the major element of the wireless technology: the antenna. In this case, an antenna occupying a limited space should be miniaturized in order to operate at the desired communication bands. However, as the electrical size of the antenna decreases, its performance degrades dramatically and it becomes limited in bandwidth, efficiency, and directivity. Classical size reduction techniques with material loading and geometry shaping of the antenna suffer from narrow bandwidth and low radiation efficiency. On the other hand, attempts to increase the directivity of small antennas using superdirective arrays are also associated with low radiation efficiency and very narrow bandwidth. To overcome these drawbacks, we propose boosting the performance of compact antennas using embedded reactive loads. By properly placing loads (active or passive) inside the antenna, it is possible to control the currents to significantly enhance the antenna performance in terms of bandwidth and directivity. Yet, for a successful loading criteria, it is mandatory to analyze the modes that are naturally supported by the antenna under study. These are called the characteristic modes, which provide deep physical insights about the behaviour of the antenna and its radiating modes. By combining this theory with and optimization algorithm, it becomes possible to optimally manipulate the currents inside the antenna using reactive loads to achieve wideband, superdirective and efficient designs
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28

Aqbi, Sadiq. "Improving the Performance of Dual Linear Polarization Antennas with Metamaterial Structures." Doctoral thesis, Universitätsbibliothek Chemnitz, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-233539.

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In this dissertation, the operation of dual-linear polarized antennas is considered in order to provide ideal performance suited for several applications including polarimetric synthetic aperture radar (SAR), wireless and satellite communications. The underlying objectives realized in this work are reported as design realizations of dual-linear polarized antennas with low cross polarization patterns and high isolation between ports that employ special properties of the electromagnetic metamaterial (MTM) structures. Some of these key properties appear as negative permittivity, negative permeability, negative refractive index, and antiparallel nature of the phase velocity and the group velocity. The antenna design is carried out at two frequencies, 5.5 GHz and 10 GHz, and key physical issues that affect the operation of dual-linear polarization operation antennas are treated in light of electromagnetic MTM properties. It’s well known that a dual linear polarized antenna poses a big challenges such as cross polarization patterns and high mutual coupling between two input ports. Therefore, these drawbacks are key topic that receive significant attention in literature which reports on how to mitigate these drawbacks, however, at the expense of complexity of the antenna structures. The MTM structures have received considerable coverage in antenna research for obtaining size reduction, directivity enhancement, and beam steering. For this purpose, different MTMs structures are chosen in this thesis for achieving additional improvements, while keeping the antenna design as simple as possible, something which is very difficult to accomplish using conventional design methods
In der folgenden Dissertation wird der Einsatz von zweifach linear polarisierten Antennen zur idealen Ausführung von verschiedenen Anwendungen, einschließlich von polarimetrischen Synthetic Aperture Radar (SAR), kabellose und satellitengestützte Kommunikation, diskutiert. Die Ziele dieser Arbeit werden dargestellt durch die Gestaltung von zweifach linear polarisierten Antennen mit gering Kreuz-Polarisationsmustern und die starke Isolation zwischen den Ports durch die einzigartigen Eigenschaften der Strukturen des elektromagnetischen Metamaterials (electromagnetic metamaterial; MTM). Einige dieser Eigenschaften treten als negative Permittivität, negative Permeabilität, negativer Brechungsindex und als antiparallel Richtungen (Gegenvektor) der Phasen-und Gruppengeschwindigkeit auf. Somit wird die Antennengestaltung auf zwei Frequenzen übertragen, 5,5GHz und 10 GHz, und die Ausführung der zweifach linearen Polarisation wird durch die elektromagnetischen Eigenschaften des MTM illustriert. Weil die Kreuzpolarisationsmuster und starke gegenseitige Koppelung zwischen zwei Input-Ports bei einer zweifach linear polarisierten Antenne große Schwierigkeiten bereiten, werden diese im Großteil der Fachliteratur als Schwerpunkte gesetzt, was zu einer Milderung der Nachteile führte, jedoch dafür die Komplexität der Antennenstruktur zunahm. Die Vielfalt an MTM ist ein bedeutender Teil im Bereich der Antennenforschung einschließlich der Größenverkleinerung, der Verbesserung der Richtcharakteristik und der Strahlensteuerung. Für diesen Zweck werden in dieser Dissertation verschiedenste MTM Strukturen ausgewählt um weitere Verbesserungen der Antennenstruktur zu ermöglichen und gleichzeitig die Einfachheit der Struktur zu bewahren, was mit konventionellen Gestaltungsmethoden nur schwer zu erreichen ist
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Dakhli, Saber. "Augmentation de la performance des antennes miniatures inspirées par métamatériaux : conception d'antennes, inspirée par métamatériaux." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S029/document.

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Le travail de cette thèse concerne la conception de nouvelles architectures d'antennes miniatures ou multifréquences en utilisant la technique inspirée des métamatériaux. Les antennes proposées sont munies de nouvelles formes d'éléments parasites qui permettent d'obtenir des structures compactes et donc facilement intégrables dans les terminaux mobiles. Par la suite, l'étude et la conception d'antennes directives et reconfigurables en diagramme de rayonnement par la technique inspirée des métamatériaux a été menée. En première partie, une étude paramétrique sur les paramètres pertinents de la structure a été effectuée afin de bien comprendre le fonctionnement de celle-ci. En deuxième partie, des antennes miniatures et directives sont proposées. Finalement, de nouvelles structures directives et reconfigurables en diagramme de rayonnement sont présentées
The work of this thesis concerns the design of new architectures of miniature antennas by using the concept of metamaterials-inspired.The proposed antennas integrate new shapes of parasitic elements that allow to obtain compact structures and therefore easily integrated into mobile devices
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30

Lai, Hau Wah. "Wideband meandering probe-fed patch antenna /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ee-b19887383a.pdf.

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Thesis (Ph. D.)--City University of Hong Kong, 2005.
"Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 144-153).
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31

Lindberg, Peter. "Wideband Active and Passive Antenna Solutions for Handheld Terminals." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7445.

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32

Sethi, Waleed Tariq. "Optical antennas for harvesting solar radiation energy." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S129/document.

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Au cours des dernières années, la communauté scientifique s'est intéressée de plus en plus à l'acquisition de sources d'énergie renouvelables vertes et propres par rapport aux combustibles fossiles traditionnels. Le rayonnement solaire est une source particulièrement abondante d'énergie renouvelable qui a été largement utilisée dans les véhicules, les machines et les bâtiments, entre autres. Il y a généralement deux manières différentes d'utiliser l'énergie solaire: la chaleur et l'électricité. La principale motivation de ce travail de thèse est d'utiliser cette abondante source d'énergie pour produire une petite fraction de la tension et du courant continu de sortie. Puisque le spectre solaire se situe dans les longueurs d'onde à l'échelle nanométrique ou dans la bande térahertz, les antennes optiques seront utilisées comme une nouvelle technologie de nanotechnologie pour capter et récolter l'énergie solaire. Les antennes optiques ont des propriétés similaires à celles de leurs homologues micro-ondes, mais leur avantage réside dans des moyens sans précédent pour adapter les champs électromagnétiques dans tous leurs aspects et applications. Par conséquent, avec les détails mentionnés ci-dessus, l'idée principale de cette thèse est de capturer le rayonnement infrarouge solaire et l'utiliser pour produire une tension continue de sortie. La première partie de cette thèse est consacrée à la compréhension du fonctionnement de la collecte d'énergie par radiofréquence (RF) et à la présentation d'un concept de rectenna. La deuxième partie traite de l'introduction et de la simulation d'antennes optiques à base de résonateurs diélectriques (DR) car elles offrent moins de pertes à la bande THz. Deux conceptions de DR différentes sont proposées fonctionnant à la fréquence centrale de 193,5 THz (longueur d'onde 1550 nm). La troisième partie traite de la contribution principale à ce travail en termes de conception, simulation et fabrication d'une antenne optique Yagi-uda à haut gain et large bande. La technique de lithographie par faisceau d'électrons est utilisée pour réaliser la structure proposée. En dehors de la conception de l'élément unique Yagi-uda, diverses configurations de réseau ont été simulées avec la réalisation d'un réseau d'éléments 100 x 100 fabriqué sur un substrat de silicium. Pour produire une certaine quantité de tension de sortie, deux techniques ont été utilisées pour tester le réseau d'antennes optiques Yagi-uda. La première technique impliquait l'intégration du réseau Yagi-uda avec une diode fermionique du commerce qui produisait une tension de sortie de 0,15 V par excitation à partir d'une lumière visible et de 0,52 V par excitation directe à partir d'un laser à 1550 nm. La deuxième technique est basée sur la dissipation thermique entre des métaux dissemblables produisant une tension de sortie. Quatre lasers à longueurs d'onde différents (532 nm, 650 nm, 940 nm et 1550 nm) ont excité trois conceptions de nantenna réalisées. Parmi ces conceptions, la tension de sortie maximale de 0,82 V a été produite par le réseau Yagi-uda lorsqu'il est excité via un laser de 1550 nm
Recent years have witnessed an increased interest by the scientific community to acquire green and clean renewable sources of energy compared to traditional fossil fuels. Solar radiation is one particular abundant source of renewable energy that has been widely applied in vehicles, machines, and buildings, among others. There are generally two different ways in which solar energy is used – heat and electricity. The main motivation of this thesis work is to utilize that abundant source of energy in producing a small fraction of output DC voltage and current. Since the solar spectrum lies in the nano scale wavelengths or terahertz band, optical antennas as a novel nano fabrication technology will be used to capture and harvest the solar energy. Optical antennas have properties similar to their microwave counterparts, but the advantage they have is in terms of unprecedented means to tailor electromagnetic fields in all its aspects and applications. Therefore, with the aforementioned details, the main idea of this thesis is to capture the solar infrared radiation and utilize it for producing output DC voltage. The first part of this thesis is dedicated to understanding the working of radio frequency (RF) energy harvesting and presenting a rectenna design. The second part deals with the introduction and simulation of optical antennas based of dielectric resonators (DR) as they offer fewer losses at the THz band. Two different DR designs are proposed working at the center frequency of 193.5 THz (1550 nm wavelength). The third part discusses the main contribution to this work in terms of design, simulation and fabrication of a high gain and wideband Yagi-uda optical antenna. E-beam lithography technique is used to realize the proposed structure. Apart for the single element Yagi-uda design, various array configurations have been simulated with realization of a 100 x 100 elements array fabricated on a silicon substrate. To produce a certain amount of output voltage, two techniques were deployed in testing the realized Yagi-uda optical antenna array. The first technique involved integration of the Yagi-uda array with a commercial fermionic diode that produced output voltage of 0.15 V via excitation from a visible light and 0.52 V with direct excitation from a 1550 nm laser. The second technique is based on thermal dissipation among dissimilar metals producing an output voltage. Four different wavelength (532 nm, 650 nm, 940 nm and 1550 nm) lasers excited three realized nantenna designs. Among these designs, the maximum output voltage of 0.82 V was produced by the Yagi-uda array when excited via 1550 nm laser
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33

Jusoh, Tajudin Mohd Taufik. "Study and design of reconfigurable antennas using plasma medium." Phd thesis, Université Rennes 1, 2014. http://tel.archives-ouvertes.fr/tel-01060295.

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Plasma is the 4th state of matter with complex permittivity that can be exploited to give advantages in communication system. Its negative permittivity has been studied in many research papers and it was proven to have similar characteristics as metal material in terms of electrical conductivity. While keeping permeability in the positive region, plasma will respond to electromagnetic waves in the similar manner as metal. Therefore, this thesis aimed to use plasma as an alternative to metal in the construction of reconfigurable antennas. The first part of this thesis is dedicated to characterize a plasma model based on the commercially available plasma source. Since there are many type of plasma source in terms of their electrical properties and physical shapes, it is important to characterize a particular plasma source so that it can be modeled in simulations to construct other types of plasma antennas. The second part presents the realization of plasma reflector antennas. Two types of plasma reflector antennas have been simulated, fabricated and measured at 2.4 GHz. The first one is are round reflector antenna (RRA) and the second one is corner reflector antenna (CRA). The performances of RRA have been validated and it was proven to provide beam shaping and beam scanning capability. The measured radiation patterns are in a good agreement with simulation ones. The capability of RRA is exceptional since it can steer its main beam from 0° up to 360°. Moreover, the scanning gain remains the same as the main beam is being moved from one direction to another. The CRA that has been introduced in this thesis is a novel design since it integrates two corner-reflector antennas on a single ground plane. The CRA offers three beam shapes which are electrically switchable from one shape to another. The CRA was simulated, fabricated and finally its performances were validated throughout a series of agile measurements. The measured reflected radiation patterns are in good agreements with the simulation ones. The measured gains of the RRA and CRA are 5 dB higher than the gain of classical monopole antenna with an identical size of finite ground plane. The fourth part deals with plasma as radio waves radiator. Two plasma antennas using commercially available U-shaped compact fluorescent lamp (CFL) have been fabricated and measured and it was proven that these antennas can be to radiate radio signal. The last part discusses about radar cross section performance of the plasma reflector antennas. The two plasma reflector antennas (RRA and CRA) were tested and measured for their RCS performance.
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Barro, Oumar Alassane. "Design and manufacturing reconfigurable antennas using plasma." Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S068/document.

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Le plasma est le quatrième état de la matière avec une permittivité complexe qui peut être exploitée pour donner des avantages aux systèmes de communications. Entre autres, une permittivité négative lui permet d'avoir des caractéristiques similaires aux matériaux métalliques en termes de conductivité électrique. Depuis de nombreuses années, les antennes plasma ont été étudiées en raison de leur capacité à être conductrices ou transparentes vis-à-vis des ondes électromagnétiques. Le principal avantage de l'utilisation d'antennes à base de plasma au lieu d'éléments métalliques est qu'elles permettent un contrôle électrique plutôt que mécanique. Par conséquent, cette thèse vise à utiliser le plasma comme une alternative au métal dans la construction des antennes reconfigurables. La première partie de cette thèse est consacrée à l'état de l'art sur l'utilisation du milieu plasma dans les systèmes de communications. Une lampe fluorescente spirale utilisée comme une cage de Faraday afin de protéger des antennes est présentée dans la deuxième partie. Deux types d'antennes (patch et monopôle) fonctionnant à 2,45 GHz sont placés à l'intérieur de cette lampe spirale. La troisième partie se focalise sur les réseaux d'antennes utilisant des tubes plasma pour reconfigurer l'ouverture du diagramme de rayonnement dans le plan H. Deux types de réseaux d'antennes sont étudiés : le premier est un réseau de patches imprimés et le second est un réseau d'antennes à fentes permettant de supporter des hautes puissances. La quatrième partie traite l'utilisation du plasma comme élément rayonnant. Deux antennes plasma (monopole et dipôle) utilisant une lampe fluorescente disponible dans le commerce ont été étudiées. Tous les systèmes antennaires présents dans cette thèse ont été simulés, fabriqués et mesurés
Plasma is the 4th state of matter with complex permittivity that can be exploited to give advantages in communication systems. Its negative permittivity allows to have similar characteristics as metal material in terms of electrical conductivity. Since many years, plasma antennas have been studied due to their ability to be conductor or transparent for electromagnetic waves. The main advantage of using plasma antennas instead of metallic ones is that they allow electrical control rather than mechanical one. Therefore, this thesis aimed to use plasma as an alternative to metal in the design of reconfigurable antennas. The first part of this thesis is dedicated to the state of the art on plasma in communication systems in order to protect antennas. The second part presents the use of plasma spiral lamp as Faraday Shield effect. Two types of antennas (patch and monopole) operating at 2.45 GHz are placed inside this plasma spiral lamp. The third part discusses about reconfigurable antennas using plasma tubes and in order to reconfigure the half-power-beam-width of the radiation pattern in H plane. Two types of antenna array have been studied: The first one is a printed patches antenna array and the second one is a slotted antenna array allowing high power utilization. The fourth part deals with plasma as radiating element. Two plasma antennas using commercially available fluorescent lamp have been studied. All the antenna systems presented in this thesis have been simulated, manufactured and measured
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35

Zhang, Tieren, University of Western Sydney, of Science Technology and Environment College, and School of Engineering and Industrial Design. "Applications of microwave holography to the assessment of antennas and antenna arrays." THESIS_CSTE_EID_Zhang_T.xml, 2001. http://handle.uws.edu.au:8081/1959.7/770.

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Gabor's original holography, which is the basic theory of modern microwave holographic techniques, is introduced. By computer simulations, it is demonstrated that the conventional holographic approach can be used as a tool to reconstruct aperture field distributions of an antenna with some constraints. Computer simulations of the theory and technique of the improved microwave holographic approach originally introduced by Rahmat-Samii et al. are carried out. The results show that it can be used for surface distortion diagnosis of large reflector antennas. The physical optics integral formulation is derived by general solutions of the vector wave equations. The necessary theory , which is needed to reconstruct the aperture field from near-field measurements both in a rectangular coordinate system and in a cylindrical coordinate system is developed. It is based on the plane wave spectrum and the vector wave modal expansion of an electromagnetic field. By using a simple dipole and other well-defined antennas, computer simulations have been performed. The results show that the technique is rigorous and applicable. It is also demonstrated that the sampling intervals and the number of sampling points should be chosen carefully in order to obtain a satisfactory resolution of the reconstructed aperture field. Furthermore, the simulations carried out in this work reveal that the real aperture field distribution of a dipole antenna has a maximum point at each end of the antenna. This characteristic can only be obtained at a very close distance to the antenna. This study also reveals the significant contributions of the evanescent waves to the aperture reconstruction. A simple but effective method for examining the evanescent waves from the measured near-field is also presented. By using dipoles and other well known antennas and antenna arrays, the experiments were carried out. The experimental results provide reasonable good agreements with the simulations. The technique proposed is effective and accurate.
Doctor of Philosophy (PhD)
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Revankar, U. K. "Three-Layer Electromagnetically Coupled Circular Microstrip Antennas." Thesis, Indian Institute of Science, 1995. https://etd.iisc.ac.in/handle/2005/241.

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Presented in this thesis are the following experimental and theoretical investigations carried out on the three-layer electromagnetically coupled (EMC) circular microstrip antennas and their arrays. 1.Three-Layer EMC Circular Microstrip Antenna A three-layer EMC circular microstrip antenna consists of a probe-fed circular microstrip patch having two parasitically excited circular microstrip patches (without ground planes) stacked above it, with air gaps in between successive substrates. In the "inverted" configuration, the parasitic patches are on the lower (nearer to the driven substrate) surface of the substrate. An exhaustive experimental study of the resonant frequencies, input impedance, impedance bandwidth and radiation characteristics of this antenna, has been carried out for both the "normal" and the "inverted" configurations. Based on this experimental study, the design and optimisation of the antenna have been discussed and experimentally tested. In the S-band, it is found that an impedance bandwidth as high as 20 percent coupled with good patterns, high gain and low cross-polarisation levels, have been obtained. 2.Three-Layer EMC Circular Microstrip Antenna Arrays Experimental work has also been carried out on linear arrays of three-layer EMC circular microstrip antennas. The design of a linear array both in the E- and H- planes, of the three-layer microstrip antennas in their "normal" as well as "inverted" configurations, has been discussed and realisation carried out. Impedance bandwidths of the arrays have been experimentally found to be the same as that of the three-layer antenna element High gain and good pattern shape with sidelobes as well as cross-polarisation levels better than -20 dB through a scan angle of 40°, have been realised. A study of the mutual coupling between two-layer as well as three-layer EMC circular patch elements has also been carried out for the useful range of interelement spacings. 3.Theoretical Analysis of Resonant Frequencies of Multilayer Patch Structures Theoretical investigations have been carried out on the resonance properties of single-layer and multilayer EMC patch structures employing the full-wave analysis based on spectral domain immittance approach. The impedance Green's functions for all these structures have been derived from the combination of equivalent transverse transmission lines concept Galerkin's method is employed in the spectral (Hankel) transform domain where two sets of disk current expansions are used for obtaining die characteristic equation. By solving the characteristic equation, the resonant frequencies are obtained for various values of the parameters of the layered antenna.
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37

Revankar, U. K. "Three-Layer Electromagnetically Coupled Circular Microstrip Antennas." Thesis, Indian Institute of Science, 1995. http://hdl.handle.net/2005/241.

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Abstract:
Presented in this thesis are the following experimental and theoretical investigations carried out on the three-layer electromagnetically coupled (EMC) circular microstrip antennas and their arrays. 1.Three-Layer EMC Circular Microstrip Antenna A three-layer EMC circular microstrip antenna consists of a probe-fed circular microstrip patch having two parasitically excited circular microstrip patches (without ground planes) stacked above it, with air gaps in between successive substrates. In the "inverted" configuration, the parasitic patches are on the lower (nearer to the driven substrate) surface of the substrate. An exhaustive experimental study of the resonant frequencies, input impedance, impedance bandwidth and radiation characteristics of this antenna, has been carried out for both the "normal" and the "inverted" configurations. Based on this experimental study, the design and optimisation of the antenna have been discussed and experimentally tested. In the S-band, it is found that an impedance bandwidth as high as 20 percent coupled with good patterns, high gain and low cross-polarisation levels, have been obtained. 2.Three-Layer EMC Circular Microstrip Antenna Arrays Experimental work has also been carried out on linear arrays of three-layer EMC circular microstrip antennas. The design of a linear array both in the E- and H- planes, of the three-layer microstrip antennas in their "normal" as well as "inverted" configurations, has been discussed and realisation carried out. Impedance bandwidths of the arrays have been experimentally found to be the same as that of the three-layer antenna element High gain and good pattern shape with sidelobes as well as cross-polarisation levels better than -20 dB through a scan angle of 40°, have been realised. A study of the mutual coupling between two-layer as well as three-layer EMC circular patch elements has also been carried out for the useful range of interelement spacings. 3.Theoretical Analysis of Resonant Frequencies of Multilayer Patch Structures Theoretical investigations have been carried out on the resonance properties of single-layer and multilayer EMC patch structures employing the full-wave analysis based on spectral domain immittance approach. The impedance Green's functions for all these structures have been derived from the combination of equivalent transverse transmission lines concept Galerkin's method is employed in the spectral (Hankel) transform domain where two sets of disk current expansions are used for obtaining die characteristic equation. By solving the characteristic equation, the resonant frequencies are obtained for various values of the parameters of the layered antenna.
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38

Hamouda, Hafedh. "Conception d'antennes miniatures intégrées à leur support pour applications en télémédecine mobile." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4062.

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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
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39

Schlub, Robert Walter, and n/a. "Practical Realization of Switched and Adaptive Parasitic Monopole Radiating Structures." Griffith University. School of Microelectronic Engineering, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20040610.112148.

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Switched and adaptive parasitic monopole array radiating structures are investigated. Antenna design is orientated toward increasing practicability for implementation in terrestrial wireless communication systems. A number of antennas are designed with the aid of optimization and commercial simulation software. Simulation procedure was verified with the experimental manufacture and measurement of the arrays. The antennas presented in this thesis comprise an active monopole surrounded by a ring of parasitic monopoles. Parasitic radiators are constructed with static loading to enable simple experimental realization. Beam positions of an electrically steered equivalent antenna are thus simulated. Antenna symmetry ensures the beam can be reproduced throughout the azimuth. Complex antenna geometries require antenna design through optimization. A genetic algorithm is employed with HFSS and NEC for electromagnetic analysis. The robust optimization method couples with simulation software flexibility to provide an effective design tool for arbitrary structures. The genetic algorithm is employed strictly for design and not complete structural optimization. Dual band, five and six element switched parasitic antennas are presented. Lumped elemental loading along the radiators provide resonance and directed radiation at two GSM frequencies. Load value, radiator dimension and spacing are incorporated as design parameters. Experimentally built, 10dB return loss bandwidths of 17.2% and 9.6% and front to back ratios of 12.6dB and 8.4dB at 900MHz and 1900MHz respectively are measured. To reduce the ground requirements of monopole arrays, a skirted ground structure for switched parasitic antennas is analyzed. A six element switched parasitic monopole array with conductive ground skirt exhibits a front to back ratio of 10.7dB and main lobe gain of 6.4dBi at 1.575GHz. Radiation is not elevated despite lateral ground terminating at the parasitic elements. Skirt height is observed to linearly control radiation elevation, depressing the principal lobe through 40 degrees from 23 degrees above the horizontal. The Electronically Steerable Passive Array Radiator or ESPAR antenna is an adaptive parasitic monopole array. An ESPAR radiating structure incorporating a conductive ground skirt is designed for operation at 2.4GHz. Utility is confirmed with a frequency sensitivity analysis showing consistent electrical characteristics over an 8.1% bandwidth. The antenna design is improved with optimization to reduce average principal lobe elevation from 25 degrees to 9.7 degrees.
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40

Schlub, Robert Walter. "Practical Realization of Switched and Adaptive Parasitic Monopole Radiating Structures." Thesis, Griffith University, 2004. http://hdl.handle.net/10072/366803.

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Switched and adaptive parasitic monopole array radiating structures are investigated. Antenna design is orientated toward increasing practicability for implementation in terrestrial wireless communication systems. A number of antennas are designed with the aid of optimization and commercial simulation software. Simulation procedure was verified with the experimental manufacture and measurement of the arrays. The antennas presented in this thesis comprise an active monopole surrounded by a ring of parasitic monopoles. Parasitic radiators are constructed with static loading to enable simple experimental realization. Beam positions of an electrically steered equivalent antenna are thus simulated. Antenna symmetry ensures the beam can be reproduced throughout the azimuth. Complex antenna geometries require antenna design through optimization. A genetic algorithm is employed with HFSS and NEC for electromagnetic analysis. The robust optimization method couples with simulation software flexibility to provide an effective design tool for arbitrary structures. The genetic algorithm is employed strictly for design and not complete structural optimization. Dual band, five and six element switched parasitic antennas are presented. Lumped elemental loading along the radiators provide resonance and directed radiation at two GSM frequencies. Load value, radiator dimension and spacing are incorporated as design parameters. Experimentally built, 10dB return loss bandwidths of 17.2% and 9.6% and front to back ratios of 12.6dB and 8.4dB at 900MHz and 1900MHz respectively are measured. To reduce the ground requirements of monopole arrays, a skirted ground structure for switched parasitic antennas is analyzed. A six element switched parasitic monopole array with conductive ground skirt exhibits a front to back ratio of 10.7dB and main lobe gain of 6.4dBi at 1.575GHz. Radiation is not elevated despite lateral ground terminating at the parasitic elements. Skirt height is observed to linearly control radiation elevation, depressing the principal lobe through 40 degrees from 23 degrees above the horizontal. The Electronically Steerable Passive Array Radiator or ESPAR antenna is an adaptive parasitic monopole array. An ESPAR radiating structure incorporating a conductive ground skirt is designed for operation at 2.4GHz. Utility is confirmed with a frequency sensitivity analysis showing consistent electrical characteristics over an 8.1% bandwidth. The antenna design is improved with optimization to reduce average principal lobe elevation from 25 degrees to 9.7 degrees.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Microelectronic Engineering
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41

McFadden, Michael. "Analysis of the equiangular spiral antenna." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31726.

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Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2010.
Committee Chair: Scott, Waymond; Committee Member: Eslinger, Owen; Committee Member: Ingram, Mary; Committee Member: Peterson, Andrew; Committee Member: Smith, Glenn. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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42

Mayhew-Ridgers, Gordon. "Development and modelling of new wideband microstrip patch antennas with capacitive feed probes." Thesis, Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-09162004-083016.

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43

Moretti, Angelo. "Estudo do brim Santista visando aplicações em antenas têxteis." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259178.

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Orientador: Hugo Enrique Hernández Figueroa
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-18T02:42:50Z (GMT). No. of bitstreams: 1 Moretti_Angelo_M.pdf: 24209106 bytes, checksum: 508d580f17f75e3268a4804a1f255b60 (MD5) Previous issue date: 2011
Resumo: A caracterização eletromagnética do tecido brim Santista, através de medições experimentais e cálculos analíticos da constante dielétrica e tangente de perda desse material foi apresentada de forma pioneira. Para esse propósito foi implementado um confiável e rigoroso método de medição que é exposto em detalhes. A possibilidade da utilização do tecido brim Santista como material dielétrico em dispositivos de radio frequência foi demonstrada de forma irrefutável pelo desenvolvimento, projeto e construção de uma antena têxtil utilizando como substrato este material. O adequado desempenho do protótipo da antena é também mostrado
Abstract: The electromagnetic characterization of Santista denim fabric, through experimental measurements and analytical calculations of the dielectric constant and loss tangent of this material was introduced for the first time. For this purpose it was implemented a reliable and accurate measurement method that is exposed in detail. The possibility of the use of Santista denim fabric as dielectric material in radio frequency devices has been irrefutably demonstrated by the development, design and construction of a textile antenna composed of the substrate with Santista denim, whose proper performance is shown here
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
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44

Leonard, Cathy Wood. "Optical feeds for phased array antennas." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80079.

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This thesis investigates optical feed methods for phased array antennas. The technical and practical limitations are analyzed and an optimum design is determined. This optimum optical feed is a two-beam interferometric approach which uses acoustooptic phase control. The theory is derived; a computer model is developed; and the limitations are determined. Design modifications are suggested which reduce limitations and greatly extend the range of applications.
Master of Science
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45

Aguilà, Moliner Pau. "Estudio de las propiedades de radiación de partículas resonantes con aplicaciones en sistemas de comunicaciones." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/402268.

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El sector de las radiocomunicaciones ha experimentado un drástico desarrollo estos últimos años. Entre ellos, los sistemas de comunicaciones inalámbricos han sufrido un gran crecimiento en la sociedad moderna motivado por el elevado número de servicios en que se pueden aplicar (por ejemplo radiodifusión, telefonía móvil, posicionamiento por satélite o bien identificación por radiofrecuencia). Esto ha motivado la investigación de nuevos dispositivos de microondas con diferentes y mejores prestaciones. La tendencia más extendida actualmente consiste en utilizar tecnologías planares para la realización de los elementos radiantes (típicamente parches metálicos o dipolos de media longitud de onda), lo que permite obtener diseños de bajo coste y fácilmente integrables con el resto de circuitería impresa. Puesto que estos dispositivos son progresivamente más compactos, un aspecto clave también es la búsqueda de técnicas para reducir las dimensiones finales de las antenas así como mejorar su funcionalidad. Una metodología aplicada ampliamente con anterioridad consiste en cargar las antenas impresas con estructuras resonantes (provenientes del campo de los metamateriales) para reducir su frecuencia de operación así como lograr un funcionamiento multifrecuencia. Recientemente, sin embargo, se ha presentado otra alternativa basada en utilizar un resonador Split Ring Resonator trabajando a la segunda resonancia como elemento radiante puesto que muestra unas propiedades de radiación interesantes en términos de eficiencia de radiación e impedancia de entrada. El objetivo principal de esta tesis ha sido, por tanto, explotar el comportamiento de esta partícula (y otras configuraciones derivadas) a la segunda frecuencia de resonancia como radiador para mejorar las prestaciones de las antenas planares convencionales en una variedad de aplicaciones. Esto abarca las antenas microstrip, las agrupaciones de antenas y, en último término, las superficies polarizadoras.
The radiocommunication sector has suffered a rapid development in recent years. Among them, wireless communications systems have shown a great growth in modern society due to the high number of services in which they can be applied (e.g. radio broadcasting, mobile telecommunications, satellite navigation or radio frequency identification). This has motivated a research of new microwave devices with different and improved features. The current trend is to use planar technologies for the realization of radiating elements (typically metallic patches or half-wavelength dipoles), which allows to obtain low cost designs that can be easily integrated with all the printed circuitry. Since these devices are more and more compact, a key point is also the search for techniques to reduce the final dimensions of the antennas as well as to improve their functionality. A widely applied methodology is to load the printed antennas with resonant structures (coming from the field of metamaterials) to reduce their operating frequency as well as to achieve multifrequency operation. Recently, however, another alternative has been proposed based on using a Split Ring Resonator working at the second resonance as a radiator since it shows interesting radiation properties in terms of its radiation efficiency and input impedance. Therefore the main objective of this thesis has been to exploit the behavior of this resonant particle (and other derived configurations) at the second resonant frequency as a radiating element to improve the performance of conventional planar antennas in a variety of applications. This includes microstrip antennas, antenna arrays and, moreover, polarizer sheets.
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46

Tursunniyaz, Muhammadeziz. "Conformal Inkjet Printed Antennas for Small Spacecraft." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7161.

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Although small spacecraft are small in size and light in weight compared to the conventional satellites, they can offer lots of possibilities for space exploration, scientific observation, data collection and telecommunication. Also, they cost a lot less money than the conventional satellites, and the scientific missions can be planned in a relatively short period of time by using the COTS (Commercial Off-The-Shelf) materials. However, there is a big challenge for the small spacecraft that is the limited surface area of the small spacecraft and the outnumbered components to be mounted on the surface of the small spacecraft. The most obvious one is that the competition for the limited real estate between the antenna and solar cells. UAVs, also known as drones, have become so popular that it is not only used for military and scientific applications, but also they are available for recreational use for ordinary people. Although they are getting smaller in size so that one can put them in his pocket or on his palm, they are becoming multifunctional, which requires more sensors to be mounted on the surface of the drone to achieve its multifunctionality. For example, a recreational drone can not only take pictures and videos, but also it can transmit the picture or video in real time to the operator, which needs a camera to take the picture or videos and needs an antenna to transmit the recorded data to the operator. This requires that the limited surface area needs to be efficiently used in order to accommodate the multiple needed components. This thesis presented a faster, better and cheaper way of inkjet printing conformal antennas on the cover glass of the solar cells of the small spacecraft or on the wing or other parts of the UAV body to integrate the antenna with the solar panels of the CubeSats or with or directly printing the antenna on the UAV body to efficiently use the limited real estate. Several meshed and solid patch antennas printed on a space certified AF32 glass substrate using the printing procedure outlined in this thesis and measured to verify the effectiveness of the inkjet printing procedures. A high gain reflectarray with optical transparency of 95% was inkjet printed on space certified AF32 glass and BOROFLOAT glass and measured to verify the antenna performance and solar panel efficiency. Measurement results showed that the inkjet printed reflectarray integrated on top of the solar panel has a gain of 21.5 dB. The solar panel efficiency was dropped by around 6% due to the inkjet printed reflectarray on glass. A simple conformal dual-band antenna for UAV application was designed with ANSYS HFSS and fabricated in the lab using a foam substrate. The measured antenna performances agreed well with the simulation results. This dual-band antenna also can be inkjet printed directly on the wing or other parts of the UAVs using the printing techniques discussed in this thesis.
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47

Mohammadzadeh, Galehdar Amir. "The Space Filling Meander Antennas for RFID Applications." Thesis, Griffith University, 2009. http://hdl.handle.net/10072/366547.

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A novel wire meander antenna is introduced for Radio Frequency Identification applications. The aim of this research was to find design rules rather than finding the best performing antenna. The limitations to small antennas performance are explored and reviewed to establish a guideline for new designs. Radiation efficiency was chosen as performance factor for measuring antenna quality. A method of moments technique based on the summation of segment currents and segment loss is introduced for finding the efficiency of wire antennas in free air. It compared favourably with two different results obtained using the finite element method (radiation pattern integration and Wheeler cap). The results were verified using two commercial available software HFSS and NEC. The efficiency of a resonant dipole was found to be proportional to the inverse square root of the conductivity. For a typical RFID meander line antenna in free space the relationship was found to be more severe. All 2D meander antennas with the same physical length in a given area were designed and simulated. The most efficient and longest electrical antennas were constructed. The simulation results were confirmed by practical measurements. A figure of merit was introduced to compare these performances with theoretical limits. Based on these antennas it is concluded that those structures with segments close to the feed have opposite current direction and usually have higher input impedance and efficiency. The idea was extended to 3D meander antennas and the same design rules as 2D meanders were used. The 3D meander antennas were placed on a conducting ground plane. Unlike 2D antennas, these antennas are capable of working near a conducting ground. This means 3D antennas are less affected by the environment around them. The two most significant shortcomings of RFID technology are: tag cost and performance. Both issues were addressed through the introduction of a new tapering method for antennas. Not only can the performance and cost be improved but the impact of tags on environment can be reduced by using this method. An optimization regime was required to find the best perform meander antenna in a given space. A Genetic Algorithm was chosen to find the best perform 2D meander antenna among all the possible solutions. A path finding optimization regime such as Ant Colony proved to be a better option. By using ACO a Pareto-Front was found for the performance of 2D meander antennas in a given area. It was shown that the efficiency is capped regardless of the track width and number of grid points mapping the area.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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48

Puente, Baliarda Carles. "Fractal antennas." Doctoral thesis, Universitat Politècnica de Catalunya, 1997. http://hdl.handle.net/10803/398784.

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Las antenas son dispositivos esencialmente de banda estrecha; es decir, su comportamiento es altamente dependiente de la frecuencia de operación. La relación entre la longitud de onda de trabajo y el tamaño de la antena condiciona enormemente sus prestaciones. Ello implica que es complicado realizar antenas que funcionen de la misma forma en varias frecuencias, o que tengan un tamaño mucho menor que la longitud de onda. En esta tesis se introduce el diseño fractal de antenas como una posible alternativa para abordar este tipo de problemas. En particular, se muestra como las propiedades geométricas de autosimilitud y dimensión no entera, que son características de los objetos fractales, pueden ser útiles en el diseño de antenas multifrecuencia (multibanda) y de antenas pequeñas. A lo largo de la Tesis se muestran varios resultados experimentales, numéricos y teóricos que confirman este hecho. Tras revisar las restricciones más comunes de las antenas clásicas, la tesis empieza enunciando teóricamente el comportamiento multibanda de las antenas con geometría fractal. El estudio se particulariza entonces al caso de agrupaciones fractales de antenas y a factores de agrupación fractales. Se demuestra que las agrupaciones fractales ideales tienen un comportamiento multibanda y que las versiones implementables de dichas estructuras Ideales conservan algunas de las propiedades multibanda. La antena de Sierpinski fue la primera verificación experimental de que se podía construir una antena fractal multibanda. A lo largo de la tesis se introduce la nueva geometría de la antena y sus propiedades fundamentales. Se ensayan también varias modificaciones de la estructura inicial, tales como variaciones en el ángulo del vértice de alimentación, variaciones en la inclinación de la antena, del espaciado entre bandas, etc. También se describe como otras formas fractales aleatorias poseen también propiedades multibanda.
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49

Kvapil, Michal. "Plasmonic Antennas." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-234590.

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Tato disertační práce pojednává o plazmonických anténách. Rezonanční vlastnosti plazmonických antén jsou studovány teoreticky i experimentálně. Teoretické výpočty jsou prováděny v programu Lumerical FDTD Solutions užitím numerické metody konečných diferencí v časové doméně. Pro experimentální studium byly antény vyrobeny pomocí elektronové litografie. Rezonanční vlastnosti vyrobených antén jsou studovány fourierovskou infračervenou spektroskopií. Práce se zaměřuje na studium rezonančních vlastností antén vyrobených na vrstvě nanokrystalického diamantu. Dále zkoumá možnost využití antén jako plazmonického senzoru funkcionalizovaného k detekci streptavidinu. Nakonec je představena anténa tvaru písmene V, u které dochází v důsledku porušení symetrie antény ke směrovému rozptylu dopadajícího světla. Tato směrovost se ovšem projevuje jen na vlnových délkách blízkých kvadrupólovému módu antény.
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50

Elghannai, Ezdeen Ahmed. "NOVEL METHOD TO CONTROL ANTENNA CURRENTS BASED ON THEORY OF CHARACTERISTIC MODES." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471871173.

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