The baluns are the key components in balanced circuits such balanced mixers, frequency multipliers, push–pull amplifiers, and antennas. Most of these applications have become more integrated which demands the baluns to be in compact size and low cost. In this thesis, a new approach about the design of planar balun is presented where the 4-port symmetrical network with one port terminated by open circuit is first analyzed by using even- and odd-mode excitations. With full design equations, the proposed balun presents perfect balanced output and good input matching and the measurement results make a good agreement with the simulations. Second, Yagi-Uda antenna is also introduced as an entry to fully understand the quasi-Yagi antenna. Both of the antennas have the same design requirements and present the radiation properties. The arrangement of the antenna’s elements and the end-fire radiation property of the antenna have been presented. Finally, the quasi-Yagi antenna is used as an application of the balun where the proposed balun is employed to feed a quasi-Yagi antenna. The antenna is working in the S-band radio frequency and achieves a measured 36% fractional bandwidth for return loss less than -10 dB. The antenna demonstrates a good agreement between its measurement and simulation results. The impact of the parasitic director on the antenna’s performance is also investigated. The gain and the frequency range of the antenna have been reduced due to the absence of this element. This reduction presents in simulation and measurement results with very close agreement.

There has been a rapid growth of terrestrial and satellite communications in the last few decades of the 20th century. This has resulted in a heavy congestion of low microwave bands and has been a major driving force for exploring the upper microwave and millimeter-wave frequencies. One of the main requirements for a successful shift to the new frequency spectrum is the availability of high power solid-state transmitters. Solid-state devices such as diodes or transistors have been able to meet such demands when their output signals are combined using space-level power combining methods that avoid conduction losses, which become pronounced at millimeter wave frequencies. In this thesis, theoretical and experimental investigations are carried out into the spatial power combiners (SPCs) which employ active planar arrays formed by transistor amplifiers whose input and output ports are equipped with planar radiating elements. The SPC structures include the reflection-type combiner using the tile configuration of planar array and the transmission-type combiner using tile or tray configurations of planar arrays. The frequency bands chosen for the designing and testing of prototypes are X- and Ku-band. The first stage of the investigation concerns the 10 GHz reflection-type power combiner structure formed by a phased planar microstrip reflectarray (MRA) of 37-element dual-feed aperture coupled microstrip patch antennas equipped with open-circuit stubs as phasing components. The experimental tests reveal poor radiation performance and hence poor power combining efficiency of this structure. These results indicated the need for theoretical investigations into the operation of this type of SPC. The study of the unit cell of this power combiner reveals that the phase of an open-circuit stub does not increase linearly as a function of the stub length and its range is limited to less than (about is required for proper functioning). This finding, forms the basis for extending the investigations into alternative phasing mechanisms of a MRA which would offer a phasing range exceeding . A phasing mechanism exploiting variable size stacked patches is chosen. In order to accurately determine the phasing of the reflected wave, a theory based on an equivalent unit cell waveguide approach (WGA) is proposed and developed. The proposed theory is computationally efficient and is proven to be accurate compared with benchmark results published by other researchers. Following the verification, an offset feed 161-element two-layer printed MRA prototype with patches of variable size is designed and developed for operation in Ku-band. The test results aim at verifying the validity of applying a unit cell WGA to designing passive and active MRAs. The next investigations, which are presented in the thesis concern increasing operational bandwidth of the transmission-type SPC in tile configuration. The designs presented so far in the open literatures were based on edge-feed microstrip patch antennas as radiating elements of individual active stages and featured a narrow-band performance. In order to overcome this shortcoming, stacked patch (SP) microstrip antennas as receiving and transmitting elements in an active transmitarray (TXA) are proposed. For the aim of testing the proposed concept, a 16-element SP TXA is designed for operation in X-band. Two identical hard horn antennas with an approximately uniform field across the aperture for signal launching and collecting complete the design and development of this space-level power combiner. The performance of the developed device is assessed experimentally and an increased operational bandwidth is demonstrated. The final structure being investigated in the thesis project is the transmission-type SPC in tray configuration. This power combining structure employs a travelling wave antenna of uniplanar quasi-Yagi type as a radiating element to achieve broad-band operation. The investigated SPC is formed by seven trays of uniplanar quasi-Yagi antenna. In order to achieve uniform and in-phase excitation of individual trays, which is required to obtain high power combining efficiency, hard horn antennas and Schiffman phase shifters are employed in the design of this space-level combiner. The proposed device is developed and its performance is assessed through experiments. The work performed as part of this Ph.D. thesis project has resulted in 5 journal papers and 11 refereed conference papers. This acceptance rate supports the claim of the originality and significance of the research undertaken as part of the thesis project.

Orientador: Prof. Dr. Carlos Eduardo Capovilla / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2016. / A tecnologia metamaterial vem sendo estudada cientificamente e suas propriedades prometem efeitos inovadores em suas aplicações. A possibilidade de manipular o comportamento eletromagnetico em um dispositivo cercado por metamateriais abre portas para a criação e otimização de novos dispositivos. Qualquer sistema que envolva dispositivos de microondas, optica e antenas, está na grade dos beneficiados por essa tecnologia. As principais caracteristicas dos metamateriais são a refração negativa e as caracteristicas intrinsecas do material com valores negativos. Assumindo esse cen'ario, nesse trabalho ser'a projetada uma célula metamaterial inspirada no conceito de lente de Lenz, que permite uma amplificação do fluxo de energia magnética na região central da estrutura. Essa célula será reconfigurada para sua implementação na estrutura de antenas planares, operando na faixa de 2,4 GHz. Tr¿es modelos de antenas são utilizadas nesse estudo, uma quasi-Yagi , uma PIFA e completando a teoria um arranjo com três PIFAs. A disposição das celulas é feita de forma periódica e estrão, assim como diagramas de radiação extraidos das simulações e testes experimentais. As conclusões são obtidas com referência nesses resultados e por meio de comparações das configurações das antenas com e sem as celulas metamateriaias em sua estrutura. / The metamaterial technology has been studied scientifically and its properties promise innovative effects in their applications. The possibility of manipulating the electromagnetic behavior on a device surrounded by metamaterials opens doors for the creation and optimization of new devices. Any system that involves microwave devices, optics and antennas is on the grid of those benefited by this technology. The main characteristics of the metamaterials are the negative refraction and the intrinsic characteristics of the material with negative values. Assuming this scenario, in this work will be projected a metamaterial cell inspired by the concept of Lenz lens, which allows an amplification of the magnetic flux in the central region of the structure. This cell will be reconfigured for its implementation in the planar antenna structure, operating in the 2.4 GHz range. Three antennas are used in this study, a quasi-Yagi, a PIFA and completing the theory a PIFA array with three elements. The arrangement of the cells is made periodically and strategically in the antenna structure, aiming for improvements in its performance. The characterization of these antennas is carried out by means of reflection and transmission parameters, as well as radiation diagrams extracted from the simulations and experimental tests. The conclusions are achieved with reference in these results and through comparisons of the antenna configurations with and without the metamaterial cells in their structure.

Made available in DSpace on 2014-12-17T14:55:33Z (GMT). No. of bitstreams: 1 FlaviaCC_Capa_ate_pag15.pdf: 8751469 bytes, checksum: df79b8a134d4a6869e65f7ed508775af (MD5) Previous issue date: 2009-11-17 / ln this work, planar quasi- Y agi antennas are investigated based on the concept of the classic Y agi_Uda antennas. These antennas represent improvements on the topologies of the antennas existing printed because they present characteristics of broad bandwidth, excellent radiation diagrams and simple construction. New configurations are adapted for the driver of the antennas, introducing patches elements into the driver. These new configurations are named Patches Elements Anteonas (PEA). This adaptation is obtained from simulations that are executed usiog the software C8T Microwave 8tudio 5. After doing the optimizations, procedures for construction and measurement ofthe prototypes are executed in order to improve the performance of the antennas in such way that they could be used in wireless communication applications, such as Bluetooth, WLAN' s and Wi-Fi. Next, the quasi- Y agi antennas are studied in order to implement them in arrangements. The arrangements construction is based 00 the best driver configuration of the antenna developed in this work. First, a linear arrangement composed by two elements of quasi?Yagi antennas is constructed in such way that the radiation characteristics and the mutual coupling effects could be analyzed. After that, a 90? angle arrangement composed by two elements is studied to observe the effect of circular polarization. Experiments are executed in order to evaluate the arrangements performance. The experimental results show that the analysis made in this work is efficient and accurate. The numerical values obtained for the analyzed parameters of each structure developed are compared with the experimental values. 80, it is possible to observe a good concordance between them. Finally, some future works proposals are presented / Neste trabalho, antenas planares quasi-Yagi s?o estudadas com base no conceito das antenas Yagi-Uda cl?ssicas. Estas antenas representam melhorias sobre as topologias das antenas impressas existentes por apresentarem caracter?sticas de banda larga, excelentes diagramas de irradia??o e constru??o simples. Novas configura??es s?o adaptadas para o driver das antenas, introduzindo elementos patches sobre o driver. Essas novas configura??es s?o chamadas de Antenas de Elementos Patches (AEP). Esta adapta??o ? obtida realizando simula??es de otimiza??o com o aux?lio do software CST Microwave Studio 5. Ap?s as otimiza??es, procedimentos para constru??o e medi??o dos prot?tipos s?o realizados com o objetivo de melhorar o desempenho das antenas para aplica??es de comunica??es sem fio, tais como Bluetooth, WLAN's e Wi-Fi. Posteriormente, as antenas quasi- Yagi s?o estudadas com o intuito de implement?-Ias em arranjos. A constru??o dos arranjos baseia-se na melhor configura??o do driver da antena desenvolvida por este trabalho. Primeiramente, um arranjo linear com dois elementos de antenas quasi-Yagi ? constru?do de tal forma que as caracter?sticas de irradia??o e o efeito do acoplamento m?tuo pudessem ser analisados. Em seguida, um arranjo composto por dois elementos dispostos sob um ?ngulo de 900 ? estudado para se observar o efeito da polariza??o circular. Experimentos s?o executados para avaliar o desempenho dos arranjos. Os resultados dos experimentos demonstram que a an?lise efetuada neste trabalho ? eficiente e precisa. Os valores num?ricos obtidos para os par?metros analisados em cada estrutura desenvolvida s?o comparados com os valores experimentais. Com isso, ? poss?vel observar uma boa concord?ncia entre eles. Por fim, algumas propostas para a realiza??o de trabalhos futuros s?o apresentadas

This thesis presents various integrated antenna solutions for different types of systems and applications, e.g. wireless sensors, broadband handsets, advanced base stations, MEMS-based reconfigurable front-ends, automotive anti-collision radars, and large area electronics. For wireless sensor applications, a T-matched dipole is proposed and integrated in an electrically small body-worn sensor node. Measurement techniques are developed to characterize the port impedance and radiation properties. Possibilities and limitations of the planar inverted cone antenna (PICA) for small handsets are studied experimentally. Printed slot-type and folded PICAs are demonstrated for UWB handheld terminals. Both monolithic and hybrid integration are applied for electrically steerable array antennas. Compact phase shifters within a traveling wave array antenna architecture, on single layer substrate, is investigated for the first time. Radio frequency MEMS switches are utilized to improve the performance of reconfigurable antennas at higher frequencies. Using monolithic integration, a 20 GHz switched beam antenna based on MEMS switches is implemented and evaluated. Compared to similar work published previously, complete experimental results are here for the first time reported. Moreover, a hybrid approach is used for a 24 GHz switched beam traveling wave array antenna. A MEMS router is fabricated on silicon substrate for switching two array antennas on a LTCC chip. A concept of nano-wire based substrate integrated waveguides (SIW) is proposed for millimeter-wave applications. Antenna prototypes based on this concept are successfully demonstrated for automotive radar applications. W-band body-worn nonlinear harmonic radar reflectors are proposed as a means to improve automotive radar functionality. Passive, semi-passive and active nonlinear reflectors consisting of array antennas and nonlinear circuitry on flex foils are investigated. A new stretchable RF electronics concept for large area electronics is demonstrated. It incorporates liquid metal into microstructured elastic channels. The prototypes exhibit high stretchability, foldability, and twistability, with maintained electrical properties. / wisenet