Microwave Metamaterial Applications using Complementary Split Ring Resonators and High Gain Rectifying Reflectarray for Wireless Power Transmission

In the past decade, artificial materials have attracted considerable attention as potential solutions to meet the demands of modern microwave technology for simultaneously achieving component minimization and higher performance in mobile communications, medical, and optoelectronics applications. To realize this potential, more research on metamaterials is needed. In this dissertation, new bandpass filter and diplexer as microwave metamaterial applications have been developed. Unlike the conventional complementary split ring (CSRR) filters, coupled lines are used to provide larger coupling capacitance, resulting in better bandpass characteristics with two CSRRs only. The modified bandpass filters are used to deisgn a compact diplexer. A new CSRR antenna fed by coplanar waveguide has also been developed as another metamaterial application. The rectangular shape CSRRs antenna achieves dual band frequency properties without any special matching network. The higher resonant frequency is dominantly determined by the outer slot ring, while the lower resonant frequency is generated by the coupling between two CSRRs. The proposed antenna achieves about 35 percent size reduction, compared with the conventional slot antennas at the low resonant frequencies. As a future alternative energy solution, space solar power transmission and wireless power transmission have received much attention. The design of efficient rectifying antennas called rectennas is very critical in the wireless power transmission system. The conventional method to obtain long distance range and high output power is to use a large antenna array in rectenna design. However, the use of array antennas has several problems: the relatively high loss of the array feed networks, difficultiy in feeding network design, and antenna radiator coupling that degrades rectenna array performance. In this dissertation, to overcome the above problems, a reflectarray is used to build a rectenna system. The spatial feeding method of the reflectarray eliminates the energy loss and design complexity of a feeding network. A high gain rectifying antenna has been developed and located at the focal point of the reflectarray to receive the reflected RF singals and genterate DC power. The technologies are very useful for high power wireless power transmission applications

Reconfigurable Leaky Wave Antenna based on Metamaterial Substrate Integrated Waveguide for 5G oriented beamsteering application

This work presents the study and the development of a Leaky Wave Antenna, based on a Composite Right-Left Handed transmission line and a Substrate Integrated Waveguide. The antenna system is designed to work in the frequency band of 26 GHz - 30 GHz, demonstrates beamsteering functionalities and a high gain. The conducted study is envisioned in the background of the fifth generation mobile networks (5G), in order to fulfil the requirements for the realization of a small cell antenna

Metamaterial

In-depth analysis of the theory, properties and description of the most potential technological applications of metamaterials for the realization of novel devices such as subwavelength lenses, invisibility cloaks, dipole and reflector antennas, high frequency telecommunications, new designs of bandpass filters, absorbers and concentrators of EM waves etc. In order to create a new devices it is necessary to know the main electrodynamical characteristics of metamaterial structures on the basis of which the device is supposed to be created. The electromagnetic wave scattering surfaces built with metamaterials are primarily based on the ability of metamaterials to control the surrounded electromagnetic fields by varying their permeability and permittivity characteristics. The book covers some solutions for microwave wavelength scales as well as exploitation of nanoscale EM wavelength such as visible specter using recent advances of nanotechnology, for instance in the field of nanowires, nanopolymers, carbon nanotubes and graphene. Metamaterial is suitable for scholars from extremely large scientific domain and therefore given to engineers, scientists, graduates and other interested professionals from photonics to nanoscience and from material science to antenna engineering as a comprehensive reference on this artificial materials of tomorrow

Técnicas para avaliação e minimização de acoplamento em sistemas de agregados de antenas

The evolution of modern MIMO systems has led them to increasingly operate at frequencies around millimeter waves in the search for greater bandwidth, as well as in the search for greater antenna gains, and beamforming or spatial filtering capabilities. For this, the high density of antennas in a short space alerts to the appearance of undesirable phenomena, such as the mutual coupling between the elements, which degrade the performance of these systems, making it necessary to find techniques to minimize this effect. In this dissertation, this problem was analyzed, and solutions are presented that allow the reduction of this negative effect in antenna aggregates. In this sense, two printed structures were developed, with properties associated with metamaterials, one in the shape of a U and the other with a variation resulting from the joining of two rings. Subsequently, a comparative study was carried out in simulation of the impact of the two structures in different situations (with patch antennas calibrated to 8.4GHz), finally the results obtained by simulation were compared with the measurements obtained in the laboratory for arrays of 4 elements with and without the U-shaped metamaterials, and the effect of these structures on the array was analysed.A evolução dos sistemas MIMO modernos tem levado estes a operar cada vez mais em frequências em torno de ondas milimétricas na procura de maiores larguras de banda, assim como na procura por maiores ganhos das antenas, e capacidade de beamforming ou filtragem espacial. Para isso, essa elevada densidade de antenas num curto espaço alerta para o aparecimento de fenómenos indesejáveis, como são o acoplamento mútuo entre os elementos, que degradam a performance destes sistemas, tornando-se necessário encontrar técnicas para minimizar esse efeito. Nesta dissertação esta problemática foi analisada, e são apresentadas soluções que possibilitam a redução deste efeito negativo em agregados de antenas. Nesse sentido, foram desenvolvidas duas estruturas impressas, com propriedades associadas aos metamateriais, propriedades estas que têm ganho bastante relevo nas últimas décadas na melhoria de sistemas MIMO em vários aspetos, uma em forma de U e outra com uma variação resultante da junção de dois anéis. Posteriormente foi feito um estudo comparativo em simulação do impacto das duas estruturas em diferentes situações (estando as antenas patch calibradas para 8.4GHz), sendo finalmente comparados os resultados obtidos por simulação com as medidas obtidas em laboratório para arrays de 4 elementos com e sem os metamateriais em forma de U e analisou-se o efeito destas estruturas no agregado.Mestrado em Engenharia Eletrónica e Telecomunicaçõe