Research On Metamaterial Multi-frequency Antenna And High Isolation MIMO Antenna

Metamaterials are becoming more and more important in the current electromagnetic microwave research and new materials science fields.The specific performances can be obtained such as perfect lens effect,inverse Doppler effect,and backward wave characteristics by designing the relevant size and shape of the metamaterial structures.The negative permeability and negative permittivity of metamaterials provide a new direction and ideas for us to design antennas.In this thesis,three new metamaterial elements are designed based on the existing metamaterial theory.These metamaterial elements are applied in monopole antennas and MIMO antennas to improve the performances of the original antennas.The research work in this thesis includes:Three metamaterial units with different structure and size are designed.These three different elements have negative permeability at 3.5 GHz or 5.5 GHz.These metamaterial elements are loaded on the traditional single-frequency monopole antenna,and the currents are coupled through the metamaterial elements to stimulate additional work frequency band.So the original two single-frequency antennas can work in dual-band and triple-band respectively while the antenna radiation characteristics and impedance matching are still good after loading metamaterials elements.The metamaterial element with negative permeability at the frequency of 5.5 GHz is applied to the two-element MIMO antenna.The purpose is to improve the isolation between the MIMO antenna elements radiation and reduce the coupling of MIMO antennas.In this thesis,two ways of loading metamaterials are used to improve the isolation of the MIMO antennas.Two decoupling isolation plates with metamaterial units are placed vertically between the two rectangular patches MIMO antenna in the first solution.The second solution is to load the metamaterial unit on both sides of the MIMO antenna radiating units.The isolations in the two solutions are improved by 8 d B and 7 d B respectively compared with the original MIMO antennas showing significant decoupling effect.The results exhibits there is very small effects on the frequency and bandwidth of antennas.Even if the distance of the MIMO antenna unit is reduced from ? / 5 to ? / 10,the effect of decoupling between antennas in the first resolution remains quite well.The second decoupling solution offers a simple structure and easy accomplishment to improve the isolation between MIMO antennas.