Circularly Polarized Tightly Coupled Antenna Based On Metasurface

Metamaterials,which have strong capability of manipulating electromagnetic waves,are commonly composed of subwavelength unit cells with a specific geometry arranged in a regular or irregular layout.The material characteristics of metamaterial depends on the structure and spatial arrangement of basic unit.Metamaterial antennas designed by traditional antennas combined with metamaterials not only enrich the types of antennas,but also provide a new way for the breakthrough of the development bottleneck that antennas have encountered,further promoting the development of wireless communication technology.In this paper,the application of metamaterials in antenna design is studied,including the use of Metasurface replace the wide angle impedance matching layer in the Tightly Coupled Dipole Array(TCDA)and combined with TCDA antenna to achieve polarized conversion,The main contexts and contributions are shown as follows:1.We propose to achieve wideband linear-to-circular(LTC)polarization conversion by ultra-thin bi-layered metasurfaces.An LTC polarization conversion metasurface is designed and fabricated,which is composed of two layers of metallic pattern arrays separated by a dielectric spacer.When linearly polarized waves impinge on the bi-layered metasurface,LTC polarization conversion transmission is greater than 90% over a wide frequency range from 12.0 GHz to 18.5 GHz.Meanwhile,the axis ratio is lower than 3 dB in 11.8GHz~18.3 GHz.This wide-band and highly efficient LTC polarization conversion transmission is analyzed theoretically.The measured LTC polarization conversion transmissions are well consistent with the simulated results.2.The Matesurface structure is used to replace the Wide Angle Impedance Matching(WAIM)layer above the TCDA,and its analysis is based on the theory of equivalent transmission line theory.On this basis,The Metasurface structure of the Split-ring resonator is designed,and applying it to a TCDA antenna.The simulation results show that,like the traditional tight coupling antenna with wide Angle matching layer,it has good wide-angle characteristics.3.A TCDA antenna is designed,and two types of circular polarization array antennas are designed in different frequency bands.The first circular polarized antenna is a TCDA antenna combined with Aperture coupling Metasurface.The impedance bandwidth of the array antenna is 34.8%(VSWR<2.).Meanwhile,the axis ratio is lower than 3 dB in 5.45GHz~5.95 GHz.The second circular polarized antenna is the ultra-thin bi-layered metasurfaces combined with TCDA antenna,The impedance bandwidth of the array antenna is 55.4%(VSWR<2.).Meanwhile,the axis ratio is lower than 3 dB in 12.5GHz~15.2 GHz.Both of the antennas have good wide angular circular polarization features.