Near Zero Refractive Index Metamaterials And Their Application In Terahertz Planar Antennas

Compared to other types of antennas,planar antennas have great advantages in integration.Therefore,planar antennas have a wide range of applications in communications and imaging systems.Research and development of terahertz antennas with high gain,low profile,and planar integration have important practical significance in implementing future terahertz communication systems.It is a hot research direction in the research of terahertz antenna technology that researching and designing terahertz planar lens antennas with the characteristics about high gain.In this paper,the basic properties of Near Zero Refractive Index Metamaterial(ZIM)are studied first,and then three different ZIM units with wideband characteristics were designed.Secondly,the radiation characteristics of terahertz planar antenna were studied,and several basic terahertz planar antennas were designed.Finally,based on the study of ZIM and terahertz planar antennas,ZIM was applied to the design of terahertz planar lens antennas to increase the gain of the feed antenna to meet the performance of the antenna under the new situation.The main content of this paper is as follows:(1)Firstly,ZIM was systematically classified.Based on this,the basic properties of isotropic near-zero refractive index metamaterial(IZIM)were given.In addition,the transmission characteristics of different types of ZIMs were analyzed in detail by the transmission matrix method.Secondly,the specific method of parameter extraction of metamaterials was briefly introduced.Finally,the design principles of left-handed materials were analyzed and summarized.Based on this,the general design methods and steps of ZIM based on left-handed material design principles were summarized.(2)Two modified fishnet-shaped structures were designed by slotting at the edge of microstrip.The relative bandwidth of the transmission coefficient,whose amplitude is greater than 0.9,is 20.3% and 25.3%,respectively.The relative bandwidth of the refractive index |n|<1 is 10.2% and 12.7%,respectively.In addition,the relationship between the equivalent impedance and the transmission characteristics was analyzed.Based on this,The characteristics of the refractive index were analyzed in detail,When the frequency varies in the frequency band of the refractive index |n|<1.Further,the reason for the variation of the refractive index with frequency in the band was briefly explained.(3)The basic properties of three-dimensional anisotropic near-zero refractive index metamaterials(3-D AZIM)were studied.Based on this,the corresponding electrical and magnetic resonators were designed.According to the designed electrical and magnetic resonators,a wideband double-zero AZIM were designed respectively,and the electromagnetic characteristics of the double-zero AZIM composed of the combination of electric and magnetic resonators were analyzed.(4)The radiation characteristics of the terahertz planar antenna were studied and analyzed.And then a slot-coupled equal-division patch antenna operating at 120 GHz and a set of microstrip patch antennas operating at 112 GHz were designed.The influence of the dielectric resonator on the performance of the antenna was also emphatically studied.A dielectric resonator with a regular size covering a certain size of the radiation patch could achieve a gain improvement effect of 1d B-2d B.(5)Three different ZIM units were used as the structural unit of the lens cladding,and the effect of the lens cladding on the performance of the basic feed antenna gain was analyzed.The maximum gain of the designed lens antenna in the operating band is 14.1d B,14.76 d B,13 d B and 12.3d B,respectively.Compared to the basic reference antenna,the gain is increased by up to 7d B in the operating band.In order to further study the principle of the ZIM cladding to enhance the antenna gain,The influence of the ideal ZIM cladding loading on the dipole antenna feed was simulated and analyzed and the reason why the ZIM cladding increases the antenna gain was explained.Based on the study of ZIM characteristics and the working principle of terahertz planar antenna,this paper proposes a terahertz planar lens antenna loaded with ZIM cladding,which can effectively improve the gain of the feed antenna while ensuring the impedance and bandwidth characteristics of the antenna.