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Antenas para redes de sensores sem fios
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| 4.34 MB | Adobe PDF |
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Abstract(s)
Com a necessidade de desenvolver nós sensores mais compactos, tem aumentado a procura por antenas mais pequenas. Como a antena é um elemento crucial do módulo de rádio, a qualidade da comunicação de um nó sensor está dependente do desempenho da antena. No entanto, a redução das suas dimensões tem impacto negativo na sua eficiência, constituindo um desafio para os projetistas. O objetivo principal deste trabalho consistiu no estudo de antenas compactas para a banda ISM (Insdustry, Scientific and Medical) de 2,4 GHz, que possam ser utilizadas num ambiente de espaço livre ou integradas num ambiente típico de um nó sensor. Foram estudadas dezoito antenas, encontrando-se divididas em duas categorias: antenas metálicas e antenas impressas. As nove antenas mais compactas foram embutidas numa caixa com circuitos eletrónicos. Esta análise é importante para avaliar o projeto de uma antena tendo em consideração o ambiente final de utilização devido ao impacto que o ambiente tem sobre as características da antena. Numa primeira fase construíram-se as várias antenas e analisaram-se as características num ambiente de espaço livre, tendo-se recorrido a uma pesquisa bibliográfica, às simulações eletromagnéticas e à verificação experimental. Para concluir, as antenas mais compactas das duas categorias foram embutidas numa caixa com circuitos eletrónicos e foram estudadas em diferentes situações, de modo a avaliar a influência do equipamento e da caixa sobre as características das antenas. Estudaram-se as características de cada antena nas várias situações na caixa, fazendo-se uma comparação com as características obtidas no espaço livre. Verificou-se experimentalmente que os diagramas na caixa perdiam as características omnidirecionais nas várias situações e que a frequência central era deslocada para um valor mais baixo. Verificou-se também que as antenas impressas tornavam-se eficientes com a proximidade aos circuitos eletrónicos.
With the need to develop more compact sensor nodes, the demand for smaller antennas has increased. Since the antenna is a crucial element of the radio module, the quality of the communication of a sensor node depends on the performance of the antenna. However, the reduction of its dimensions has a negative impact on its efficiency, posing a challenge for the designers. The main objective of this project was to study compact antennas for the 2,4 GHz ISM band that can be used in a free space environment or integrated in a typical sensor node environment. Eighteen antennas were studied, which are divided into two categories: metallic antennas and printed antennas. The nine most compact antennas were embedded in a box with electronic circuits. This analysis is important to evaluate the design of an antenna considering the final environment of use due to the impact that the environment has on the characteristics of the antenna. In the first phase the various antennas were constructed and the characteristics analyzed in a free space environment, and a bibliographic search was made, to the electromagnetic simulations and to the experimental verification. To conclude, the most compact antennas of the two categories were embedded in a box with electronic circuits and were studied in different situations, in order to evaluate the influence of the equipment and the box on the characteristics of the antennas. The characteristics of each antenna were studied in the various situations in the box, making a comparison with the characteristics obtained in the free space. It was experimentally found that the diagrams in the box lost the omni-directional characteristics in the various situations and that the center frequency was shifted to a lower value. It was also found that the printed antennas became efficient with the proximity to electronic circuits.
With the need to develop more compact sensor nodes, the demand for smaller antennas has increased. Since the antenna is a crucial element of the radio module, the quality of the communication of a sensor node depends on the performance of the antenna. However, the reduction of its dimensions has a negative impact on its efficiency, posing a challenge for the designers. The main objective of this project was to study compact antennas for the 2,4 GHz ISM band that can be used in a free space environment or integrated in a typical sensor node environment. Eighteen antennas were studied, which are divided into two categories: metallic antennas and printed antennas. The nine most compact antennas were embedded in a box with electronic circuits. This analysis is important to evaluate the design of an antenna considering the final environment of use due to the impact that the environment has on the characteristics of the antenna. In the first phase the various antennas were constructed and the characteristics analyzed in a free space environment, and a bibliographic search was made, to the electromagnetic simulations and to the experimental verification. To conclude, the most compact antennas of the two categories were embedded in a box with electronic circuits and were studied in different situations, in order to evaluate the influence of the equipment and the box on the characteristics of the antennas. The characteristics of each antenna were studied in the various situations in the box, making a comparison with the characteristics obtained in the free space. It was experimentally found that the diagrams in the box lost the omni-directional characteristics in the various situations and that the center frequency was shifted to a lower value. It was also found that the printed antennas became efficient with the proximity to electronic circuits.
Description
Keywords
Antenas compactas Simulação de antenas Construção de antenas Nó sensor Compact antennas Antenna simulation Antenna construction Sensor node Engenharia Eletrotécnica - Telecomunicações . Faculdade de Ciências Exatas e da Engenharia