Yes / In this paper, balanced dual segment cylindrical dielectric antennas (CDRA) with ultra wide-band operation are reported. First a T-shaped slot and L-shaped microstrip feeding line are suggested to furnish a balanced coupling mechanism for feeding two DRAs. Performance of the proposed antenna was analyzed and optimized against the target frequency band. The proposed antenna was then modified by adding a C-shaped strip to increase the gain. The performances of both balanced antennas were characterized and optimized in terms of antenna reflection coefficient, radiation pattern, and gain. The antennas cover the frequency range from 6.4 GHz to 11.736 GHz, which is 58.7% bandwidth. A maximum gain of 2.66 dB was achieved at a frequency of 7 GHz with the first antenna, with a further 2.25 dB increase in maximum gain attained by adding the C-shaped strip. For validation, prototypes of the two antennas were fabricated and tested. The predicted and measured results showed reasonable agreement and the results confirmed good impedance bandwidth characteristics for ultra-wideband operation from both proposed balanced antennas.

Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0  37.5  5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Duas contribuiÃÃes caracteristicamente distintas, nÃo obstante correlacionÃveis num mesmo sistema de telecomunicaÃÃo, sÃo apresentadas. A primeira versa sobre antenas ressoadoras constituÃdas por novas cerÃmicas dielÃtricas à base de Fe2O3. Os materiais desenvolvidos foram caracterizados na faixa de micro-ondas. Tratam-se de dielÃtricos com baixa permissividade relativa, baixa tangente de perda, e, no caso das amostras monofÃsicas, com coeficiente de temperatura na frequÃncia de ressonÃncia negativo. Posteriormente, as antenas ressoadoras dielÃtricas de geometria cilÃndrica (CDRAs) suportadas em plano de terra retangular e alimentadas por sonda monopolar sÃo analisadas segundo critÃrios de desempenho de irradiaÃÃo, quais sejam: frequÃncia de ressonÃncia, impedÃncia de entrada, largura de banda e padrÃes de irradiaÃÃo. AlÃm de experimentaÃÃo, o seu estudo envolveu procedimento computacional, no que foi promovida a comparaÃÃo de resultados. O mÃtodo dos elementos finitos, no qual està baseado o programa comercial empregado, foi utilizado para anÃlise destas antenas. Resulta que para maiores valores de permissividade relativa de uma amostra, menores sÃo a frequÃncia em que a mesma ressoa e a sua largura de banda. Ainda, foi observado satisfatÃrio casamento de impedÃncia e padrÃes de irradiaÃÃo "broadside", o que candidata os novos materiais desenvolvidos a esta importante aplicaÃÃo. Adicionalmente, mediante empilhamento dos protÃtipos monofÃsicos examinados, foi verificada a remodelagem da largura de banda em relaÃÃo Ãs contrapartidas individuais, provavelmente devido à excitaÃÃo de modos de ordem elevada das CDRAs. A segunda contribuiÃÃo està enfocada no contexto dos guias de ondas dielÃtricos operando em frequÃncias Ãpticas. Neste cenÃrio, sÃo investigados acopladores refletores de Bragg a fibra (FBGCs), estruturas resultantes da combinaÃÃo de dois dispositivos reconhecidamente versÃteis e de ampla aplicaÃÃo: redes de Bragg e acopladores direcionais. Foram apreciados dois estudos de caso numÃricos nos quais se fez promover a interaÃÃo de sinais Ãpticos com as estruturas propostas. Na medida em que descreve com satisfatÃria precisÃo as propriedades Ãpticas dos dispositivos de interesse, o modelo matemÃtico empregado à baseado na teoria dos modos acoplados. O tratamento numÃrico à realizado mediante codificaÃÃo, em linguagem de programaÃÃo FORTRAN, de um algoritmo preditivo-corretor. Considerando regimes pulsados em termos da potÃncia operacional, o problema foi analisado no domÃnio da frequÃncia e, sobretudo, no domÃnio do tempo. Em condiÃÃes especÃficas, a possibilidade de realizaÃÃo da extraÃÃo, reconfiguraÃÃo e comutaÃÃo de pulsos, exemplos de funÃÃes essenciais ao processamento totalmente Ãptico, reforÃam a importÃncia de tais estruturas hÃbridas. / Two heterogeneous contributions to modern communication systems â although fully possible to be correlated â are presented. The first one deals with resonant antennas consisting of new dielectric ceramics based on Fe2O3. These materials characterized at microwave frequency range possess low relative permittivity, low loss tangent and, concerned with the monophasic samples, negative temperature coefficient of resonant frequency. Subsequently, the cylindrical dielectric resonator antennas (CDRAs) supported on rectangular ground plane and fed by monopole are analyzed according to the following radiation performance criteria: resonant frequency, input impedance, bandwidth and radiation patterns. Besides experimentation, the study involved computational procedure, so that the results of both can be compared. A commercial software based on the finite element method was employed to examine the CDRAs. It follows that as higher is the permittivity of a material, the lower are the frequency at which it resonates as well as its bandwidth. Satisfactory impedance matching and broadside radiation patterns are observed, what enables the materials investigated to this relevant application. Additionally, the stacking of the monophasic CDRAs prototypes resulted in bandwidth enhancement, presumably due to their excited high order modes. The second contribution focuses on dielectric waveguides operating at optical frequencies, being fiber Bragg grating couplers (FBGCs) investigated in this scenario. Indeed, they result from a combination of two versatile and widely applied devices: fiber Bragg gratings and directional couplers. Two numerical case studies related to the interaction between optical signals and structures were performed. The theoretical model observed is based on the coupled mode theory since it provides a satisfactorily accurate description of the devices optical properties. By the way, the theoretical model is coded in FORTRAN programming language according to a predictor-corrector algorithm. In terms of operational power levels, analyses are carried out in frequency and (mainly) time domains. Under specific conditions, the capability of the extraction, reshaping and switching of pulses â examples of essential functions for all-optical processing â reinforces the importance of such hybrid structures.

Les télécommunications sont devenus indispensables dans notre monde actuel. De plus, le volume des données échangées ne cesse de croître. En effet, nous pouvons transmettre nos photos, nos vidéos au monde entier. Nonobstant, nous ne voulons pas attendre pour les avoir, ce qui exige un débit de données très important et par conséquent des signaux avec des bandes passantes plus larges. Les satellites de télécommunications doivent donc s’adapter, c'est pourquoi nous proposons dans ces travaux la recherche de filtre à large bande avec une recherche de compacité et de faibles pertes. Nous nous sommes intéressés à l'utilisation de matériaux céramiques qui permettent d'obtenir de bonnes performances vis à vis de nos besoins. Notre travail est aussi rendu possible par le développement de procédés de fabrication additifs, comme par exemple la stéréolithographie, qui va nous permettre de nous affranchir fortement de règles de dessin contraignantes que nous pourrions avoir en utilisant des procédés classiques. Nous avons développé des filtres avec de larges bandes passantes autour de 4GHz. Une première étude nous a permis de rechercher des concepts qui permettent d'obtenir de forts couplages, conditions sine qua non pour réaliser ces filtres. Plusieurs concepts sont présentés ainsi que leur fabrication et leur mesures. Nous avons ainsi démontré expérimentalement que les concepts proposés, à base de pièces monoblocs céramiques, sont capables de produire des filtres à bandes passantes supérieures à 60 % (voire même 110 % pour une version améliorée). / Every day, the data exchanges increase thanks to the new technologies. We can keep our files, our pictures, our videos online to have an access anywhere on the planet (for now). In this way, the data output of the telecommunication systems has to be increased in order to satisfy the more and more demanding users. One way to allow this is to increase the bandwidths of the different signals, making possible to transmit more data at the same time. In this work, we will develop wide bandpass filters dedicated to space telecommunications. For that purpose, we need them to be compact, with low insertion loss and a limited number of parts to assemble. Consequently, we are interested to use resonators made with ceramic materials that permits to reach such properties. Moreover, these materials are compatible with stereolithography, an additive manufacturing process. Such technology is here very useful for our purpose since its design freedom allows the creation of almost all kind of geometries. To realize such wide bandpass filters, we need strong couplings between the different resonators and also for the accesses, so we will present our studies focused on reaching these specific objectives. Then, we will present different designs of wide bandpass filter around 4GHz. After different generation of ceramic based components, we are be able to experimentally create a 60% bandwidth (even 100% for our last version) very compact bandpass filter filling the objectives of this PhD thesis.

Práce se zabývá buzením vyšších módů v kvádrových a válcových dielektrických rezonátorových anténách pro účely zvýšení zisku. Pomocí numerických simulací jsou studovány vlastnosti a limity anténních prvků. Je zkoumáná vzájemní vazba mezi dielektrickými rezonátorovými anténami pracujícími s vyššími vidy a na základě výsledků je možno usuzovat o vhodnosti těchto prvků k popužití v anténních řadách. V práci je popsán analytický model efektivní permitivity perforovaných dielektrik, který respektuje anizotropní povahu tohoto materiálu. Model je založen na Maxwell Garnettové aproximácií nehomogenních materiálů. Dále jsou studovány povrchové vlny na perforovaných substrátech a je ověřena použitelnost teoretického modelu i v tomto případě. Nakonec jsou studovány dielektrické rezonátorové antény vytvořené pomocí perforací v dielektrickém substrátu a je demonstrováno zhoršení určitých vlastností takových antén.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20377号 / 工博第4314号 / 新制||工||1668(附属図書館) / 京都大学大学院工学研究科電気工学専攻 / (主査)教授 篠原 真毅, 教授 和田 修己, 教授 大村 善治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

K-Band (18 to 26 GHz) dielectric resonator oscillators are typically used as a local oscillator in most K-Band digital transmitter/receiver topologies. Traditionally, the oscillator itself is made up of an active device, a dielectric resonator termination network, and a passive load matching network. The termination network embodies a cylindrical high permittivity dielectric resonator that is coupled on the same plane as a current carrying transmission line. This configuration provides an adequate resonance needed for oscillation but has some limitations. In order to provide a high Q resonance the entire oscillator is placed in a metal box to prevent radiation losses. This increases the overall size of the device and makes it difficult to integrate in smaller transceiver topologies. Secondly, a tuning screw is required to help excite the dominant mode of the resonator to achieve the high Q response. This can cause problems in precision due to the mechanical jitter of the screw inherent in mobile devices. By embedding this resonator inside the substrate it is possible to realize a very high Q resonance at a desired frequency and remove the need for a metal cavity and tuning screw. An additional advantage can be seen in terms of overall size reduction of the oscillator circuit. To demonstrate the feasibility of utilizing a dielectric resonator embedded within a substrate, a K-Band oscillator proof of concept has been designed, fabricated, and tested. The oscillator is comprised of a low noise active transistor device, an embedded k-band dielectric resonator and a passive transmission line load network. All elements within the oscillator are optimized to produce a steady oscillation near 20 GHz. Preliminary investigations of a microstrip resonator S-band (2-3 GHz) oscillator are first discussed. Secondly, various challenges in design and fabrication are discussed. Thereafter, simulated and measured results of the embedded DRO structure are presented. Emphasis is placed on output oscillation power and low phase noise. With further development, the entire oscillator can be embedded within the substrate leaving only the active device on the surface. This allows for a considerable reduction in material cost and simple integration with miniaturized digital transmitter/receiver devices.

Dielectric resonator antenna (DRA) technologies are applicable to a wide variety of mobile wireless communication systems. The principal energy loss mechanism for this type of antenna is the dielectric loss, and then using modern ceramic materials, this may be very low. These antennas are typically of small size, with a high radiation efficiency, often above 95%; they deliver wide bandwidths, and possess a high power handling capability. The principal objectives of this thesis are to investigate and design DRA for low profile personal and nomadic communications applications for a wide variety of spectrum requirements: including DCS, PCS, UMTS, WLAN, UWB applications. X-band and part of Ku band applications are also considered. General and specific techniques for bandwidth expansion, diversity performance and balanced operation have been investigated through detailed simulation models, and physical prototyping. The first major design to be realized is a new broadband DRA operating from 1.15GHz to 6GHz, which has the potential to cover most of the existing mobile service bands. This antenna design employs a printed crescent shaped monopole, and a defected cylindrical DRA. The broad impedance bandwidth of this antenna is achieved by loading the crescent shaped radiator of the monopole with a ceramic material with a permittivity of 81. The antenna volume is 57.0  37.5  5.8 mm3, which in conjunction with the general performance parameters makes this antenna a potential candidate for mobile handset applications. The next class of antenna to be discussed is a novel offset slot-fed broadband DRA assembly. The optimised structure consists of two asymmetrically located cylindrical DRA, with a rectangular slot feed mechanism. Initially, designed for the frequency range from 9GHz to 12GHz, it was found that further spectral improvements were possible, leading to coverage from 8.5GHz to 17GHz. Finally, a new low cost dual-segmented S-slot coupled dielectric resonator antenna design is proposed for wideband applications in the X-band region, covering 7.66GHz to 11.2GHz bandwidth. The effective antenna volume is 30.0 x 25.0 x 0.8 mm3. The DR segments may be located on the same side, or on opposite sides, of the substrate. The end of these configurations results in an improved diversity performance. / General Secretariat of Education and Scientific Research Libya

The main goals of this thesis are to design and examine heterogeneous antennas for different wireless applications of a wide variety of EM spectrum requirements: which includes WLAN 5.0 GHz, WLAN (2.45 GHz), UMTS (1.92-2.17 GHz), 2G, UMTS, LTE, ultra-wideband (UWB) applications, and MBAN applications (2.4 GHz). Various techniques for expanding bandwidth, enhancing performance, and balancing the operation have been examined through comprehensive simulated and physically fabricated models. Thereafter, a compact DRA, for UWB applications is examined. The combined resultant effects of asymmetric positioning of DRs (2, 3 and 4 Cylindrical elements), defected ground technique, dimensions, and profile of the aperture give RF designers detailed scope of the optimization process. More resonances are achieved, and the bandwidth is improved. The obtained results show that, an impedance bandwidth of 133.0%, which covers the Ultra­ Wideband band (3.6GHz - 18.0GHz), with a maximum power gain of 9dBi attained. In addition, a compact conformal wearable CPW antenna using EBG-FSS for MBAN applications at 2.4GHz is proposed. They are designed using fabric materials suitable for daily clothing. The performance of the antenna is investigated in free space, on a layered biological tissue model, and on a real human body to evaluate SAR. When the antenna is combined with an EBG-FSS structure, isolation between the antenna and the human body is introduced. The results show that the FBR is enhanced by 13 dB, the gain by 6.55dBi, and the SAR is lowered by more than 94%. The CPW antenna demonstrated here is appropriate for future MBAN wearable systems. The design, investigation, and application of water level monitoring utilizing subsurface wireless sensor are covered in this thesis. A wideband double inverted-F antenna is designed and examined to overcome signal attenuation issues. The obtained result is feasible, which has an operating bandwidth of 0.8 to 2.17GHz, with a reflection coefficient better than 10 dB. Moreover, a field trial is conducted to evaluate the robustness of the antenna under extreme conditions. A very good efficiency was also demonstrated, with losses of under 20%. Further, the results from the field experiment established that the antenna is a reliable contender for wireless communication in such challenging environments. / Libyan Ministry of Higher Education / The full text will be available at the end of the embargo: 25th May 2025

Made available in DSpace on 2014-12-17T14:55:13Z (GMT). No. of bitstreams: 1 JoemiaLGMM_TESE.pdf: 3140610 bytes, checksum: 8bdf88d29c888d95e74fd24e403e60fc (MD5) Previous issue date: 2013-06-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Ceramic substrates have been investigated by researchers around the world and has achieved a high interest in the scientific community, because they had high dielectric constants and excellent performance in the structures employed. Such ceramics result in miniaturized structures with dimensions well reduced and high radiation efficiency. In this work, we have used a new ceramic material called lead zinc titanate in the form of Zn0,8Pb0,2TiO3, capable of being used as a dielectric substrate in the construction of various structures of antennas. The method used in constructing the ceramic combustion synthesis was Self- Sustained High Temperature (SHS - "Self-Propagating High-Temperature Synthesis") which is defined as a process that uses highly exothermic reactions to produce various materials. Once initiated the reaction area in the reaction mixture, the heat generated is sufficient to become self-sustaining combustion in the form of a wave that propagates converting the reaction mixture into the product of interest. Were analyzed aspects of the formation of the composite Zn0,8Pb0,2TiO3 by SHS powders and characterized. The analysis consisted of determining the parameters of the reaction for the formation of the composite, as the ignition temperature and reaction mechanisms. The production of composite Zn0,8Pb0,2TiO3 by SHS performed in the laboratory, was the result of a total control of combustion temperature and after obtaining the powder began the development of ceramics. The product was obtained in the form of regular, alternating layers of porous ceramics and was obtained by uniaxial pressing. 10 The product was characterized by analysis of dilatometry, X-ray diffraction analysis and scanning electron microscopy. One of the contributions typically defined in this work is the development of a new dielectric material, nevertheless presented previously in the literature. Therefore, the structures of the antennas presented in this work consisted of new dielectric ceramics based Zn0,8Pb0,2TiO3 usually used as dielectric substrate. The materials produced were characterized in the microwave range. These are dielectrics with high relative permittivity and low loss tangent. The Ansoft HFSS, commercial program employee, using the finite element method, and was used for analysis of antennas studied in this work / Substratos cer?micos t?m sido investigados por pesquisadores de todo o mundo e tem despertado um grande interesse na comunidade cient?fica, pelo fato de apresentarem altas constantes diel?tricas e um excelente desempenho nas estruturas empregadas. Tais cer?micas resultam em estruturas miniaturizadas, com dimens?es bem reduzidas e de alta efici?ncia de radia??o. Neste trabalho, utilizou-se um novo material cer?mico, chamado de titanato de zinco chumbo, na forma de Zn0,8Pb0,2TiO3, capaz de ser utilizado como substrato diel?trico na constru??o de diversas estruturas de antenas. O m?todo utilizado na constru??o da cer?mica foi a S?ntese por Combust?o Auto-Sustentada a Alta Temperatura (SHS Self-Propagating High-Temperature Synthesis ) que ? definido como um processo que utiliza rea??es altamente exot?rmicas para produzir os mais diversos materiais. Uma vez iniciada a rea??o numa ?rea da mistura reagente, o calor gerado ? suficiente para tornar a combust?o auto-sustent?vel, na forma de uma onda que se propaga convertendo a mistura reagente no produto de interesse. Foram analisados os aspectos da forma??o do comp?sito Zn0,8Pb0,2TiO3 por SHS e os p?s obtidos, foram caracterizados. A an?lise consistiu na determina??o dos par?metros da rea??o para a forma??o do comp?sito, como a temperatura de igni??o e os mecanismos de rea??o. A produ??o do comp?sito Zn0,8Pb0,2TiO3 por SHS, realizada em laborat?rio, foi resultado de um controle total da temperatura de combust?o e ap?s a obten??o do p? 8 iniciou-se o desenvolvimento das cer?micas. O produto foi obtido na forma de camadas regulares e altern?ncia de porosidades e as cer?micas foram obtidas por prensagem uniaxial. O produto foi caracterizado atrav?s de an?lises de dilatometria, difra??o de raios-X e an?lise de microscopia de varredura eletr?nica. Uma das contribui??es principais deste trabalho foi o desenvolvimento de um novo material diel?trico, n?o obstante apresentado anteriormente na literatura. Portanto, as estruturas das antenas apresentadas neste trabalho foram constitu?das por novas cer?micas diel?tricas ? base de Zn0,8Pb0,2TiO3, geralmente utilizado como substrato diel?trico. Os materiais desenvolvidos foram caracterizados na faixa de micro-ondas. S?o substratos diel?tricos de alta permissividade relativa e baixa tangente de perda. O software comercial empregado, Ansoft HFSS, baseado no m?todo dos elementos finitos, foi utilizado na an?lise das antenas estudadas neste trabalho