The switched-beam antenna is one type of the smart antennas, which consists of the antenna array and the beamforming network. The four-beam smart antenna generates four beams to cover a 120¢X area, which can be used to improve the carrier-to-interference ratio and the frequency reuse of a cellular system. Due to the attractive features of microstrip antennas such as low profile, easy fabrication, and low cost, we use microstrip antennas as array elements. In this thesis, we propose a novel four-beam beamforming network which consists of a 4¡Ñ4 Butler Matrix and four 180¢X power dividers. This network is able to provide low side-lobe level. A modified Butler Matrix not only simplifies the circuit of the 8¡Ñ8 Butler Matrix, but also meet the requirement of the original Butler Matrix. From the result of measurement, the side-lobe level of each beam of the modified Butler Matrix is less than ¡V10 dB. We also show that this method is applicable to any Butler matrix.

A four-sector switchable WiMAX antenna, for indoor use in the 4.9 -5.0 GHz frequency bands, is presented. The prototype antenna is designed to provide a higher gain in a specified sector region. Furthermore, the radiation beam is electronically steerable to provide space diversity in four different sectors. Each sector of this antenna includes an array of two rectangular microstrip patches. The air gap between the bottom substrate of microstrip patches and the ground plane is increased to 3 mm, which can aid in accomplishing a high-gain and wideband design goal. A solid-state microwave switch is used to select one of the four sectors.

Array antennas are used extensively in remote sensing applications, where a highly directive beam is needed to scan a particular area of interest on the surface of the earth. The research presented here focuses on the design of different microstrip patch antenna arrays to be used in environmental sensing applications in the X and Ka frequency bands, such as measurements in Snow and Cold Land Processes (SCLP) to detect snow accumulation, snow melt, etc. The goal of this research is to produce highly integrated, low loss, and compact size antenna arrays, while maintaining low power consumption. Multilayer organic (MLO) System-on-a-Package (SOP) technology, using laminates such as Liquid Crystal Polymer (LCP) and RT/Duroid®, provides a lightweight and low cost 3D solution for the fabrication of the antenna arrays. The elements of the antenna arrays are rectangular patches. Two feeding mechanisms, aperture coupling and via feed, were implemented and compared. For the RF distribution network and interconnects, a corporate feed approach was used with reactive T-junctions, Wilkinson dividers, or both, for power division. The feed networks were designed using microstrip. The basic multilayer antenna array design consists of 3 layers of cladded laminate material. The metal layers are as follows: 1) patch antennas, 2) ground plane, 3) feed network, and 4) surface-mount components. The surface mount components would include LNA, PA, TR switch and phase shifter.

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.