Design And Application Of The Electromagnetic Metamaterials

The Electromagnetic Metamaterials is a kind of artificial medium and has some special physical properties which the conventional materials don't have. The left-handed materials, a kind of Electromagnetic Metamaterials, behave special physical properties, such as negative refraction characteristics, perfect lens characteristics, inverse Doppler characteristics and so on. Furthermore, when electromagnetic wave propagates in it, there will be left-handed relationship among electric field, magnetic field and wave vector in a certain frequency range. Because of these special properties, the research on the metamateials has been paid much attention. Various left-handed materials have been put forward, while application of the Electromagnetic Metamaterials process quickly. The purpose of this thesis is to design new left-handed materials, study the optimization method of left-handed materials with specific frequency band and to improve the microstrip antenna gain with the use of Electromagnetic Metamaterials.Based on the left and right transmission line theory and electric and magnetic resonance theory, the author designed two-side and one-side left-handed materials. Numerical simulation and parameter retrieval verified that the permittivity, permeability and refractive index of both new left-handed materials are negative in a certain frequency band, which illustrates that both new left-handed materials have left-handed properties. Then the influences of the size parameters of these two left-handed materials on the left-handed band and left-handed bandwidth are analyzed. Numerical simulations demonstrate that the theoretical analysis is valid, and it is available to design new left-handed materials by using these two different methods.In applications, the left-handed materials always be high loss and its bandwidth is narrow, so one optimization method of left-handed materials with maximized frequency bandwidth and lower loss in given frequency band is proposed, and its mathematical model is put forward too. Through the optimization, the left-handed materials with maximized frequency bandwidth and lower loss are constructed in a given frequency band. Two kinds of different left-handed structures with maximized frequency bandwidth and lower loss are acquired in different given frequency band. The design results confirm that the optimization method is applicable and accurate.A microstrip antenna with negative permeability structures is constructed. Compared to the conventional microstrip antenna, it has greater gain and bandwidth. First a two dimensional negative permeability structure is constructed. When the incident electromagnetic wave along x axis or z axis, the electromagnetic wave can't propagate in this structure. Then a microstrip antenna with negative permeability structures is constructed by loading the permeability structures to the substrate. Compared to the conventional microstrip antenna, the antenna has lower loss, greater gain and bandwidth at working frequency. Therefore, the negative permeability structures successfully suppress the surface wave propagation in the microstrip antenna, which can improve the radiation efficiency.