Design Of Broadband Metasurface Antenna Based On Characteristic Mode Analysis

Nowadays,large numbers of people pay much attention to the data transmission rate and the operating bandwidth of the communication system with the development of wireless communication technology.In the past decades,microstrip antenna is extensively used because of low profile and easy integration.However,traditional microstrip antenna cannot to meet the increasing requirement in wireless communication system.The booming development of wireless communication has driven a new generation of high-performance,multi-functional antennas.High performance antennas usually include wideband,dual-band/multi-band,dual/multi-polarized,high gain and so forth.Metasurface,as a two-dimensional planar electromagnetic metamaterial,could be widely used in high-performance antennas design due to its extraordinary physical properties.In these paper,three kinds of metasurface antennas with different performance are designed.Based on the Characteristic Mode Analysis(CMA),suitable feeding structures are selected to excite these metasurfaces.The main contents of these papers include:1.A novel wideband non-uniform metasurface antenna with stable gain is demonstrated.The non-uniform metasurface is composed of square rings and patches.Based on Characteristic Mode Analysis(CMA),two characteristic modes with the similar current direction are selected to achieve wideband operation.The non-uniform metasurface is excited by a slot antenna.The bandwidth is further broadened by assembling the resonant modes of metasurface and slot antenna,and the stable radiation performance is also achieved in a wide band.The measured results show that the-10 d B impedance bandwidth of the proposed antenna is 4.3-8.4 GHz(64.57%),and the 2 d B gain bandwidth is 4.3-6.2 GHz(36.2%)with the peak gain 9.42 d Bi.The crosspolarization level is lower than-18 d B.2.A broadband dual-polarized metasurface antenna with high isolation and low cross-polarization is proposed.A broadband metasurface with stable radiation pattern is presented by splitting the edge patches into 2 × 2 sub-array and introducing Minkowski fractal structure in the corner patches.A pair of degenerate modes of the metasurface are selected to achieve the dual-polarized operation,meanwhile,high isolation and low cross-polarization are also obtained.The metasurface is excited by two slot antennas placed orthogonally.The proposed antenna could achieve dual-polarization operation.The measured results show that the-10 d B impedance bandwidths for each port are28.9%(4.74-6.34 GHz)and 31.4%(4.62-6.34 GHz),respectively.The isolation between the two ports is higher than 31.8 d B,and cross-polarization level is better than-28 d B.3.A low-profile dual-wideband metasurface antenna is demonstrated for 4G LTE and 5G Sub-6GHz applications.Based on the characteristic mode analysis,a wideband metasurface with stable radiation pattern is proposed by introducing Minkowski fractal structure in the edge patches and scaling the corner patches.The metasurface operating in upper band is excited by a Vivaldi bowtie slot antenna,and the slot antenna serves as the radiator in lower band.The measured results show that the-10 d B impedance bandwidths in two bands are 1.7-2.78 GHz(48.2%)and 3.2-5.01 GHz(44.1%),respectively.Moreover,broadside radiation performances in two bands are obtained.