Electromagnetic Metamaterials And Its Application In Antennas

Electromagnetic Metamaterial is one of the hot spots and focuses in researches of electromagnetic theory and new material science.Electromagnetic metamaterials usually consist of periodic or aperiodic array of subwavelength units,which have many fantastic electromagnetic properties different from natural materials and can be used for regulating electromagnetic waves.Metamaterials provides a new technical approach for antenna design and optimization.Based on the above background,this thesis first studies deeply the metamaterial theory,and puts research focus on the design of new metamaterial structures and on the analysis of mutual relation of its characteristics and structure.Second,this thesis studies the characteristics enhancement of microstrip antenna and MIMO antenna with applications of electromagnetic metamaterials.As a result,three antennas are designed and experimentally verified.The specific contents of the thesis are summarized as follows:1.Different analysis methods of resonant metamaterials and non-resonant metamaterials of composite right-handed transmission line?CRLH-TL?are studied respectively.?i?For resonant metamaterials,the s-parameter inversion method is adopted to study its characteristics,and relevant formulas are derived.NRW algorithm and K-K relation algorithm are compared and analyzed to extract the equivalent parameters of the metamaterials structure.A novel planar helical resonant metamaterial structure is proposed and designed.Detailed electronic simulations and analyses are carried out.?ii?For the CRLH-TL metamaterials,the method for solving their dispersion curves is introduced.A new type of CRLH-TL metamaterial structure is proposed and designed and its dispersion characteristics are simulated and analyzed.2.For isolation enhancement application,two MIMO antennas with metamaterials loaded are designed and analyzed.?1?In order to verify the decoupling effect of metamaterials mentioned above,a high-isolation MIMO antenna loaded with metamaterials at 3.47GHz is designed.Within the impedance bandwidth range ofS₁₁?27?-10dB,the isolation(S₂₁)of the MIMO antenna is increased from 15.5dB of non-loaded case to 22.8dB of loaded case.?2?A new structure of CPW fed compact UWB MIMO antenna loaded with metamaterial units is proposed.The overall size of the antenna is32?32?1.6mm³.Loading two metamaterials structures with different sizes between the antenna units,the isolation of metamaterial is improved by 4.1dB,which meets the application requirement that the isolation is greater than 15dB in the working bandwidth of 3¹1.5GHz frequency band.The metamaterial influences on the MIMO antenna are studied and experimentally verified.3.Based on the CRLH-TL metamaterial unit proposed previously,a broadband multi-functional metasurface is designed and applied to improve the bandwidth and gain performance of the microstrip antenna.A square open-loops array are etched on the radiation patch of the rectangular microstrip antenna,and cross gaps are etched on the metal ground.Such changes causes the radiation characteristics of the antenna to become end-fired at high frequencies.The broadband high-gain microstrip antenna is obtained with a bandwidth of 3.68¹6.5GHz,an gain greater than 2dB within the working band,and a maximum peak gain of 7.76dB.Finally,the experiments based on physical processing and testing are carried out.The work conducted in of this thesis has reference values for electromagnetic metamaterials research and their application in antenna engineering.