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Thesis
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Dispozitive de microunde bazate pe structuri de tip metamaterial
Ochetan, Alexandru Bogdan
2011-10-15
Abstract: The development of the mobile communications has imposed high and conflicting demands to the microwave devices, the trend being in obtaining miniaturized devices, capable of multi-band or wideband operation, by using efficient and low cost solutions. The emergence of a new class of materials, that have electromagnetic properties not typically found in nature, known as metamaterials, has generated much interest within the research communities due to their potential to create new devices with enhanced performances. In this thesis, there are proposed and analyzed two types of microwave devices that are based on metamaterial structures, implemented as Composite Right/Left-Handed – CRLH transmission lines: radiating devices used as antennas and non-radiating devices used as power dividers. The proposed antennas are classified as leaky-wave and resonant type antennas. The characteristics of these devices are investigated by electromagnetic simulations and by practical measurements and then, compared to those of conventional type devices. The proposed leaky-wave antennas are based on a new CRLH cell which allows the expansion of the radiating structure after one (1D) or two directions (2D). It is shown that the 1D leaky-wave antenna presents superior performances as compared to other antennas from the existing literature. There are also proposed different methods for improving the performances of the 1D antennas. These methods include the achievement of a symmetrical structure, the usage of transition lines and the equivalence of the CRLH structure with a higher order band-pass filter, improvements being seen for the gain, the directivity, the level of secondary lobes and the operating bandwidth. The proposed resonant antennas are of two types: shunt and series. The shunt type antenna is designed to operate in multiple, dual and controllable frequency bands and the series type antenna is matched to the outer microwave system, by using the classical filter theory and obtaining, this way, miniaturized dimensions. The designed power divider shows superior performances as compared to the ones from the existing literature. It presents miniaturized dimensions and is able to operate in three different frequency bands that cover the most common mobile communications systems. Even more, it has a low insertion loss, is balanced in phase and amplitude and its output ports are well isolated.
Keyword(s): Microunde -- Dispozitive electronice -- Teză de doctorat ; Metamateriale -- Teză de doctorat ; Antene radio -- Teză de doctorat ; materiale electrotehnice -- Teză de doctorat
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Record created 2017-02-22, last modified 2017-02-22
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