Yes / Near field imaging using microwaves in medical applications is of great current interest for its capability and accuracy in identifying features of interest, in comparison with other known screening tools. This paper documents microwave imaging experiments on breast cancer detection, using active antenna tuning to obtain matching over a wide bandwidth. A simple phantom consisting of a plastic container with a low dielectric material emulating fatty tissue and a high dielectric constant object emulating a tumor is scanned between 4 to 8 GHz with a UWB microstrip antenna. Measurements indicate that this prototype microwave sensor is a good candidate for such imaging applications. / Yorkshire Innovation Fund, Research Development Project (RDP)

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.

Submitted by Marlucy Farias Medeiros (marlucy.farias@unipampa.edu.br) on 2017-10-02T18:23:28Z No. of bitstreams: 1 Marcelo Pereira Magalhães - 2017.pdf: 16186012 bytes, checksum: dc2e2c4f42a58ebcadb895281114a36d (MD5) / Approved for entry into archive by Marlucy Farias Medeiros (marlucy.farias@unipampa.edu.br) on 2017-10-04T17:35:03Z (GMT) No. of bitstreams: 1 Marcelo Pereira Magalhães - 2017.pdf: 16186012 bytes, checksum: dc2e2c4f42a58ebcadb895281114a36d (MD5) / Made available in DSpace on 2017-10-04T17:35:03Z (GMT). No. of bitstreams: 1 Marcelo Pereira Magalhães - 2017.pdf: 16186012 bytes, checksum: dc2e2c4f42a58ebcadb895281114a36d (MD5) Previous issue date: 2017-05-12 / This thesis presents the design and analysis of an antenna array system for mobile communication services in a scenario using high altitude platforms (HAPs). For this purpose, a dual-band and dual-polarized microstrip antenna array has been designed, whereby the array should receive the signal in one band and resend it in the other operating band. These requirements have been fulfilled by using a stacked arrangement, whereby each patch has been fed by independent feed lines. Circular polarization was obtained by the use of square patches with truncated corners. Optimizations were needed so as to compensate the effects of mutual coupling on the axial ratio level. To perform the radiation pattern synthesis for the transmission function, an algorithm to calculate the required excitation coefficients was employed to steer the main beam and to control the side lobe level. Additionally to the array design, the development of the high-frequency (HF) circuitry for the retransmission is described. The design of the transmitter was done using off-the-shelf components, which have been tested individually prior to the final integration into the final layout. During the tests, the need of knowledge of the electromagnetic properties of the printed circuit layout and the active/passive components is crucial for a successful design. In order to accelerate the development of HF circuitry, a procedure to perform electromagnetic simulations of HF printed circuit boards is proposed. Experimental results demonstrated that this procedure yielded accurate engineering predictions. / Este trabalho apresenta o projeto e análise de um sistema de rede de antenas para serviços de comunicações móveis em um cenário empregando plataformas de alta altitude (HAPs). Para este fim, uma rede de antenas de microfita foi projetada para operar em dupla-banda e dupla-polarização, onde a rede deve receber o sinal em uma banda e reenviá-lo em outra. Esses requisitos foram cumpridos usando uma rede de antenas com m´ultiplas camadas, onde cada patch foi alimentado por linhas de alimentação independentes. A polarização circular foi obtida pelo uso de patches quadrados com os cantos truncados. Foram necessárias otimizações para compensar os efeitos de acoplamento mútuo no nível da razão axial. Para realizar o controle do diagrama de irradiação para o modo de transmissão, utilizou-se um algoritmo para calcular os pesos necessários para apontar o lóbulo principal e controlar o nível dos lóbulos laterais. Adicionalmente ao projeto da rede, o desenvolvimento de um circuito em alta frequência (HF) para a retransmissão foi descrito. O projeto do circuito transmissor foi realizado empregando componentes comerciais, que foram testados individualmente antes da integração final. Durante os testes em bancada, ficou evidente a necessidade de predição do comportamento eletromagnético do layout da placa de circuito impresso e dos componentes ativos/passivos para obtenção de bons resultados. Com o intuito de acelerar o processo de desenvolvimento de circuitos em HF, um procedimento para a realização de simulações eletromagnéticas de placas de circuito impresso foi proposto. Os resultados experimentais demonstraram que este procedimento produziu bons resultados.

Modern wireless communication systems call for ultra wideband operations to meet the continuous growth in the number of users of these systems. Since antenna is an integral part of any wireless communication system (transmitter or receiver), designing antennas with good gain over large bandwidth needs to be considered first. To meet the popular demand, wireless communication systems should be as cheap as possible which require antennas with small size, light weight, low profile and low cost, and that are easy to fabricate and assemble. A type of antenna that satisfies most of these requirements is the microstrip antenna. Most of the wideband techniques for microstrip antennas utilize complicated geometries such as stacked multiple metal/dielectric layers, complicated feed arrangements etc., which elude the primary attraction of microstrip antennas. On the other hand, single layer suspended configurations are considered the best choice as these are simple to fabricate and assemble. The objective of this research is to investigate simple microstrip antennas with large bandwidth. A single layer suspended microstrip configuration was chosen for the purpose. In the first part of the research, the bandwidth was increased to about 50% with linear phase characteristics by optimizing the feed configurations while retaining the overall simplicity. This study has resulted in proposing a criterion for obtaining maximum bandwidth in the suspended microstrip configuration. An analytical model has been developed for such an antenna configuration. Although several analytical tools are available for the microstrip antenna analysis, equivalent circuit based approach proves to be a simple one and offers convincingly accurate results. Another advantage of the proposed equivalent circuit modeling scheme is that it is suitable for computer aided design (CAD). In order to make this approach even more useful, the antenna designed in the first part was modified to meet desired specifications such as reduction in the air gap to make the antenna compact, symmetrical patterns, making antenna circularly polarized (LHCP or RHCP) without changing the feed configuration. Nearly symmetrical patterns were obtained throughout the band of operation by modifying the profile of patch close to the feed strip. Circular polarization (CP) operation has been obtained from the basic antenna by cutting a diagonal slot on the radiator patch. Here the slot orientation decides the type of CP i.e., LHCP or RHCP. In this work obtained of 7.1% axial ratio (3dB) bandwidth with other characteristics unaffected. The overall height of the antenna is reduced by 55% by cutting a slot and re-optimizing the feed strip dimensions. These studies emphasize flexibility offered by the design approach in realizing practical antennas for various applications.

In this study we tried to design a microstrip antenna, to get a suitable radiation pattern for a LEO satellite. Our aim is to get a radiation pattern that has a maximum power which is not in the broadside direction to the antenna surface / instead broadside radiation has a relatively lower power density. Maximum power radiation is desired to be at about 30 &ndash / 50 degrees angle beyond the normal to the antenna surface. We desire circularly polarized radiation. We used two concentric antennas / one is a circular patch at the center and the other is an annular ring which is used at the outer region. By using Ansoft Ensemble 8.0 software, we design an antenna which has a resonance frequency at 8.2 GHz. Using the result of the program we design the real antenna. The measurement results are compared with the simulation results.

In this thesis, a wideband dual polarized microstrip antenna is designed, manufactured and measured. Slot coupled patch antenna structure is considered in order to achieve the wideband characteristic. Although rectangular shaped slot coupled patch antennas are widely used in most of the applications, their utilization in dual polarized antenna structures is not feasible due to space limitations regarding the positioning of two separate coupling slots for each polarization. For a rectangular slot, the parameter that affects the amount of coupling is the slot length. On the other hand when a H-shaped slot is considered, both the length of the center arm and the length of the side legs determine the coupling efficiency. This flexibility about the optimization parameters of the H-shaped slot makes it possible to position the two coupling slots within the boundaries of the patch antenna. Therefore, H-shaped slot coupled patch antennas are studied in this thesis. In order to investigate the effects of slot and antenna dimensions on the radiation characteristics of the antenna, a parametric study is performed by analyzing the antenna structure with a planar electromagnetic field simulation software (Ansoft Designer). By the help of the experience gained through this parametric study, a dual polarized patch antenna that can be used at the base station of a cellular system (DCS: 1710&ndash / 1880 MHz) is designed. Before manufacturing the antenna, dimensions of the antenna are re-tuned by considering a finite sized ground plane in the simulations. Finally, the antenna is manufactured and measured. An acceptable agreement is obtained between the measurement and the simulation results.

Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-05-24T20:47:48Z No. of bitstreams: 1 JuanRFG_DISSERT.pdf: 3346003 bytes, checksum: 0b61d81493463a07bc096fa6a4a756d6 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-05-26T11:52:59Z (GMT) No. of bitstreams: 1 JuanRFG_DISSERT.pdf: 3346003 bytes, checksum: 0b61d81493463a07bc096fa6a4a756d6 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-05-26T11:53:54Z (GMT) No. of bitstreams: 1 JuanRFG_DISSERT.pdf: 3346003 bytes, checksum: 0b61d81493463a07bc096fa6a4a756d6 (MD5) / Made available in DSpace on 2017-05-26T11:54:25Z (GMT). No. of bitstreams: 1 JuanRFG_DISSERT.pdf: 3346003 bytes, checksum: 0b61d81493463a07bc096fa6a4a756d6 (MD5) Previous issue date: 2016-05-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The flexible microstrip antennas are devices that guarantee the development of communications systems with greater adaptability to the different types of microwaves applications .The possibility of an antenna be designed using textile materials facilitates their conditioning on systems that need is in contact or very close to the human body. The mesh fabric offers greater adaptability to the application due its flexibility. To build the antenna, is necessary check the compatibility between the knitted fabrics available and project needs. Therefore, is essential study the behavior of the electrical and physical features of each structure, analyzing also the influence of synthetic and organic fibers in performance. The characterization allows choice which fabrics is better to manufacture the antenna, is designed and built one microstrip antenna with classic rectangular geometry using the knitted fabric with better performance. The synthetic fibers have better physical characteristics that improve the adaptability of the tissue as a substrate. The electrical characteristics of the mesh fabrics they presented similar behavior as the frequency variation. In the frequency 2.45 GHz knitted fabric composed of polyester and spandex has the best actual values of relative permittivity and loss tangent thus constructed is used in the antenna design. The results show that the resonance frequency is approximately 2.68 GHz, a variation near 230 MHz, this is due to aspects of the test antenna construction / As antenas de microfitas flexíveis são dispositivos que garantem o desenvolvimento de sistemas de comunicações com maior adaptabilidade aos diversos tipos de aplicações em microondas. A possibilidade de uma antena ser projetada utilizando materiais têxteis facilita seu condicionamento em sistemas que necessitem estar em contato ou muito próximo ao corpo humano. O tecido de malha oferece maior adaptabilidade à aplicação devido a sua flexibilidade. Com o objetivo de construir a antena, é necessário verificar a compatibilidade entre os tecidos de malha disponíveis e as necessidades do projeto. Assim, é indispensável estudar o comportamento das características elétricas e físicas de cada estrutura. Analisando também, a influência das fibras sintéticas e orgânicas no desempenho. A partir da caracterização e escolha dos tecidos que comporão a antena, é projetada e construída uma antena de microfita com geometria retangular clássica utilizando o tecido com melhor desempenho. Os tecidos que contém fibras sintéticas apresentam características físicas que aumentam a adaptabilidade do tecido como substrato. As características elétricas dos tecidos apresentam comportamento semelhante quanto à variação da frequência. Na frequência de 2,45 GHz o tecido de malha composto por Poliéster e Elastano apresenta os melhores valores de permissividade relativa real e tangente de perdas, assim, é utilizado no projeto da antena construída. Os resultados demonstram que a frequência de ressonância é aproximadamente 2,68 GHz, representando uma variação aproxima de 230 MHz, isso ocorre devido a aspectos ligados a fase de construção da antena teste / 2017-05-24

Made available in DSpace on 2015-03-03T15:07:32Z (GMT). No. of bitstreams: 1 AdaildoGDAJ_DISSERT.pdf: 911535 bytes, checksum: 85d35a0c8d60343a1313312b827ff4af (MD5) Previous issue date: 2007-02-22 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / The great interest observed in wireless communication systems has required the development of new configurations of microstrip antennas, because they are easily built and integrated to other microwave circuit components, which is suitable for the construction and development of planar antenna arrays and microwave integrated circuits. This work presents a new configuration of tapered microstrip antenna, which is obtained by impressing U-slots on the conducting patch combined with a transmission line matching circuit that uses an inset length. It is shown that the use of U-slots in the microstrip antenna conducting patch excites new resonating modes, that gives a multiband characteristic for the slotted microstrip antenna, that is suitable for applications in communication systems that operates several frequencies simultaneously. Up to this date, the works reported in the literature deals with the use of Uslotted microstrip rectangular antennas fed by a coaxial probe. The properties of a linear array of microstrip patch tapered antennas are also investigated. The main parameters of the U slotted tapered microstrip antennas are investigated for different sizes and locations of the slots impressed on the conducting patch. The analysis of the proposed antenna is performed by using the resonant cavity and equivalent transmission line methods, in combination with a parametric study, that is conducted by the use of the Ansoft Designer, a commercial computer aided microwave software well known by its accuracy and efficiency. The mentioned methods are used to evaluate the effect in the antennas parameters, like resonant frequency and return loss, produced by variations of the antenna structural parameters, accomplished separately or simultaneously. An experimental investigation is also developed, that consists of the design, construction and measurement of several U slotted microstrip antenna prototypes. Finally, theoretical and simulated results are presented that are in agreement with the measured ones. These results are related to the resonating modes identification and to the determination of the main characteristics of the investigated antennas, such as resonant frequency, return loss, and radiation pattern / A demanda por novos sistemas de comunica??es sem fio (wireless communication systems) tem requerido o desenvolvimento de novas configura??es de antenas de microfita, pois estas antenas apresentam uma grande facilidade de integra??o com outros componentes de circuito que facilitam a constru??o de arranjos planares e de circuitos integrados em freq??ncias de microondas. Neste trabalho ? analisada uma nova configura??o de antena de microfita afilada, na qual s?o introduzidas fendas em U (U-slots), no patch condutor, al?m de uma reentr?ncia (inset), atrav?s de uma se??o de linha de microfita, para fins de casamento da imped?ncia de entrada. A introdu??o de uma ou v?rias fendas no patch condutor da antena de microfita excita novos modos de resson?ncia, dando ? estrutura fendida uma caracter?stica de opera??o em multibanda, que possibilita a sua utiliza??o em sistemas com freq??ncias de opera??es distintas. Os trabalhos publicados com a impress?o de fendas em U dizem respeito ? utiliza??o de patches retangulares de microfita alimentados por cabo coaxial. Tamb?m ? investigada a associa??o de antenas afiladas na composi??o de arranjos lineares. S?o examinados e discutidos diversos aspectos relacionados com as dimens?es dessa fenda e o seu posicionamento no patch da antena considerada em termos do efeito produzido nas suas principais caracter?sticas de radia??o. A an?lise da antena proposta ? efetuada atrav?s dos m?todos da cavidade ressonante e da linha de transmiss?o modificados, em combina??o com um estudo param?trico, que ? realizado atrav?s do software comercial Ansoft Designer. Estes m?todos s?o empregados para avaliar as modifica??es produzidas nas caracter?sticas eletromagn?ticas, como a freq??ncia de resson?ncia e a perda de retorno, da antena em resposta ?s varia??es introduzidas em alguns dos seus par?metros estruturais. Al?m da investiga??o te?rica, ? inclu?da uma parte experimental que consistiu no projeto, constru??o e medi??o de v?rios prot?tipos configura??o de antena considerada. Finalmente, s?o apresentados resultados te?ricos (m?todos aproximados) e simulados (Ansoft Designer), que apresentam boa concord?ncia com os das medi??es efetuadas. Estes resultados consistem principalmente na identifica??o dos modos de resson?ncia e na determina??o das caracter?sticas principais das antenas consideradas, como a freq??ncia de resson?ncia, a perda de retorno e o diagrama de radia??o

Made available in DSpace on 2014-12-17T14:55:01Z (GMT). No. of bitstreams: 1 WellingtonCA.pdf: 2479530 bytes, checksum: b3f1a9eeb71d69303b76e476fd5fe393 (MD5) Previous issue date: 2007-08-10 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work presents a study of implementation procedures for multiband microstrip patch antennas characterization, using on wireless communication systems. An artificial neural network multilayer perceptron is used to locate the bands of operational frequencies of the antenna for different geometrics configurations. The antenna is projected, simulated and tested in laboratory. The results obtained are compared in order to validate the performance of archetypes that resulted in a good one agreement in metric terms. The neurocomputationals procedures developed can be extended to other electromagnetic structures of wireless communications systems / Esta disserta??o apresenta um estudo dos procedimentos de implementa??o para a caracteriza??o de antenas patch de microfita multibanda empregadas em sistemas de comunica??es sem fio. Uma rede neural artificial do tipo percepton multicamada ? empregada para localizar as bandas de freq??ncias operacionais da antena para diferentes configura??es geom?tricas. A antena ? projetada, simulada e testada em laborat?rio. Os resultados obtidos s?o comparados a fim de validar o desempenho dos prot?tipos que resultou numa boa concord?ncia em termos m?tricos. Os procedimentos neurocomputacionais desenvolvidos podem ser estendidos a outras estruturas eletromagn?ticas de sistemas de comunica??es sem fio

Made available in DSpace on 2014-12-17T14:55:07Z (GMT). No. of bitstreams: 1 ClarissaLN.pdf: 3152047 bytes, checksum: a2e14bfa9e4c314444ebb4284dc7608b (MD5) Previous issue date: 2008-10-21 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This work presents a theoretical and experimental investigation about the properties of microstrip antennas for ultra-wideband systems. Configurations of elliptic monopoles with different eccentricities and circular monopoles are considered. Two prototypes for each antenna configuration were built, one with the typical microstrip configuration and the other is similar to the first, except for a small aperture in the ground plane. Therefore, this work proposes to modify the configuration of the ground plane of the monopoles designed adding a rectangular stub, in order to optimize and improve the performance of such structures. The obtained results show that the introduction of that rectangular aperture in the ground plane allows an improvement of the frequency response for the considered antenna propotypes. It is observed a good agreement between the measured and simulated results. Finally, some proposals for future works are presented / Este trabalho apresenta uma investiga??o te?rica e experimental sobre as propriedades de antenas de microfita para sistemas de banda ultra larga. S?o consideradas configura??es de monopolos el?pticos com excentricidades diferentes, e monopolos circulares. Foram constru?dos dois prot?tipos para cada configura??o de antena, um com a configura??o t?pica de microfita e outro similar ao primeiro, mas com uma pequena abertura no plano de terra. Assim, este trabalho objetiva modificar a configura??o do plano de terra dos monopolos projetados atrav?s da inser??o de um recorte retangular, para fins de otimiza??o e melhoria nos desempenhos das estruturas. Os resultados obtidos mostram que a introdu??o dessa abertura retangular no plano de terra permite melhorar a resposta em freq??ncia das antenas consideradas. Observa-se uma boa concord?ncia entre os resultados medidos e simulados. Algumas propostas para a realiza??o de trabalhos futuros s?o apresentadas