Novel Antennas Based On Metamaterials And Metasurfaces

Metamaterials are periodic or aperiodic materials which are composed of subwavelength structures.These materials can show some special electromagnetic properties at the macro level,so they attract more and more attentions in recent years.With the rapid development in the past nearly 20 years,great progress has been made in the field of metamaterials in both theory and engineering.In this thesis,we will focus on designing antennas based on metamaterials and metasurface.The main contents and contributions of the thesis are summarized as follows:·A high gain antenna is designed at 37.5GHz,using a gradient index lens.To decrease the error caused by the restrictions of the process,the lens is composed of two kinds of metamaterials units in the direction of the propagation of the electromagnetic wave.The two combined units can realize more values of refractive index.·A new approach is proposed to design high gain and high efficiency horn antenna with even amplitude and phase distributions.To realize even amplitude distribution,a sheet metal is inserted into the horn antenna.And a gradient index lens is located at the aperture of the antenna to correct the phase error.Full-wave simulation and experiment results prove that the antenna can possess high gain from 14 GHz to 15 GHz.·A wideband low-profile antenna is designed,using a wideband high impedance surface.The high impedance surface is composed of two kinds of unit cells which operate in different frequency bands.The surface can decrease profile of a patch antenna,and realize wide impedance match bandwidth.·A wideband low-profile antenna is designed,using a wideband linear polarization rotator surface.Comparing to the low-profile antenna based on high impedance surface,this antenna can realize wider beam width.So this antenna possess better far-field stability which means that its radiation patterns is difficult to generate grating lobes and can maintain high gain along z axis.·A new approach is presented to simultaneously control the polarization and scattering direction of an electromagnetic wave.By designing suitable structures,the metamaterials can have different functions in adjacent frequency bands.Moreover,voltage controlled diode can affect the equivalent circuit of the metamaterials.So the metamaterials can realize different functions at the same frequency,when the state of the voltage controlled diode is changed.