Study On Miniaturized Antenna Using Electromagnetic Metamaterials

With the development of signal processing technology and integrated circuit technology,mobile portable devices will become smaller and smaller. Miniaturized antennas are the urgentneeds of people which are the units to send and receive electromagnetic wave. In recent years,electromagnetic metamaterials have become a hot research topic both at home and abroad.Electromagnetic metamaterials are new types of artificial electromagnetic materials which arecomposed of small units. These units determine the macroscopic electromagnetic properties ofmaterials like the molecules and atoms in the natural materials. Electromagnetic metamaterialshave wide application prospects because of their many exotic electromagnetic properties.In this dissertation, two kinds of antenna miniaturization methods using electromagneticmetamaterials are studied which are zeroth-order resonance and slow-wave property ofelectromagnetic bandgap (EBG) structures. Firstly, it is introduced that the development processand the application in antenna miniaturization of electromagnetic metamaterials. Secondly, thezeroth-order resonance theory and the conditions for the existence of slow-wave is introduced.The equivalent circuit model is simplified and theoretically analyzed which is proposed by T.Kamging on “mushroom” type EBG structure. Finally, three types miniaturized microstripantennas are designed using zeroth-order resonance theory, EBG slow-wave theory, thecombination of fractal theory and EBG slow-wave theory respectively. These antennas have beensimulated, parameter optimized, fabricated and measured, measured results agree very well withthe theoretical analysis.The main valuable results of the dissertation are as follows:1, A new method is proposed by increasing equivalent shut capacitors on the condition ofthe whole dimensions keeping the same to further reduce the zeroth-order resonant frequency ofthe antenna.2, A method is proposed to analyze the slow-wave effect of the EBG structure, it is denotedas waveguide-method. Waveguide-method is demonstrated in theory. The slow-wave effect of“米” type EBG structure which has a coating is analyzed using waveguide-method. We can findthat coating thickness and unit height affect the slow-wave wavelength of “米” type EBGstructure seriously. The waveguide-method is applicable to all types EBG structures and solvesthe problem of how to analyze the slow-wave effect of EBG structure.3, A method is proposed to design miniaturized antenna using EBG structure as groundplane. A miniaturized microstrip antenna working at2GHz is designed by taking advantage ofthis method. The antenna is fabricated and measured, the measured results verify thewaveguide-method and the method to design miniaturized antenna using EBG structure asground plane.4, A type of miniaturized microstrip antenna which works in2.4GHz band is designed usingthe combination of fractal and slow-wave effect. The size of this antenna is only39%of theordinary microstrip antenna.