Study Of Wideband Microstrip Antenna Based On Metamaterials

In recent years,with the rapid development of wireless communication technology,the microstrip antennas with broadband,miniaturization and high gain have become one of the research hotspots.Metamaterial,as a kind of artificial composite material based on periodic element structure,can obtain special electromagnetic characteristics different from natural medium through the design and optimization of its size and physical structure.By introducing the metamaterial into the design of microstrip antenna,it can not only break through the limitation of antenna size,but also improve the antenna bandwidth and gain.Therefore,it is considered as one of the most potential schemes of antenna design.In this dissertation,several designs of microstrip antenna based on metamaterial are proposed,and the main academic contribution is summarized as follows.1.An antenna based on curved-branched metamaterial is proposed.By introducing the curved branches at both the patch and ground plane and making an angle of ? between them,the omnidirectional CP fields can be obtained in the wider azimuth planes.Also,the axial ratio(AR)bandwidth and gain of the antenna are improved.The measured results show that the proposed antenna has a 3-d B AR bandwidth of 2.05-2.7 GHz(the relative bandwidth is 27.4%).It can cover the-10-d B impedance bandwidth of 2.16-2.63 GHz.Moreover,the omnidirectional CP fields can be obtained in the planes of ? = 50°-130°.2.An artificial mu-negative transmission line(MNG-TL)is proposed.By etching dumbbell-shaped slots on the microstrip and narrow gaps on the ground plane,the zeroth-and first-order resonance(ZOR and FOR)modes of MNG-TLs can be excited.Moreover,by introducing two parallel branches at the edge of metal strips in the ground plane,the CP fields of the antenna based on MNG-TL are obtained at both resonance modes.The measured results show that the proposed antenna has a 3-d B AR bandwidths of 10.2%(from 2.33 to 2.58 GHz)and 7.7%(from 3.35 to 3.62 GHz)in lower(ZOR)and upper(FOR)bands,respectively.Meanwhile,the omnidirectional CP radiation can be formed in the azimuth planes of 30° < ? < 60° and 30° < ? < 40° in two bands,respectively.3.A dual-layer metasurface(MS)is proposed.It is composed of top MS etched four interlaced quarter arc-shaped slots and the bottom MS formed by six square metal rings.By employing the dual-layer MS to serve as a radiator and ground plane,a low-profile wideband antenna is proposed.The measured results show that the-10-d B impedance bandwidth of the MS antenna is from 2.57 to 4.12 GHz and the relative bandwidth is 46.3 %.Furthermore,the maximum gain reaches 4.17 d Bi.4.A wideband array antenna based on dual-layer MS is proposed.To achieve a broader impedance bandwidth,a symmetric circular slot which is perpendicular to the top ones is etched on the bottom metallic layer.Also,to achieve a higher gain,the dual-layer MS is placed on the radiation array.The measured results show that the impedance bandwidth of the radiation array is from 2.04 GHz to 3.74 GHz and the relative bandwidth is 58.8 %.Moreover,the maximum gain of the array antenna based on dual-layer MS is further enhanced to 9.7 d Bi.