Research On The Optimization Design Of Dual-polarization Antenna Gain Performance Based On Electromagnetic Metasurfac

Dual-polarized antennas are usually used in polarization diversity systems to deal with signal multipath problems in complicated electromagnetic environments.In order to enhance the quality of the received signal and the coverage of the system,it is necessary for antennas to have the characteristics of high gain,wide frequency band,high crosspolarization ratio,etc.At present,the design of high-performance antenna structures tends to be complicated.Now,the development of electromagnetic metasurface provides a simple and feasible way for antenna optimization.Based on the characteristics of electromagnetic metasurface and the principle of resonant cavity high gain antenna,the optimal design and research of dual-polarized antenna are carried out in this thesis.The specific work is as follows:1.A square isotropic metasurface is designed to optimize the crossed dipole antenna which is used in the direction finding system.The dipole antenna is fed by balun and realizes the unidirectional radiation and high gain by designing the four-sided bending reflector.The working frequency band of antenna is 1.7-2.8GHz.In this thesis,the electromagnetic characteristics of the metasurface are simulated and analyzed.The ±90°reflection phase bandwidth of metasurface is 1.5-3GHz,which matches well with the operating band of the antenna.Based on the principle of Fabry-Perot resonant cavity highgain antenna,the metasurface structure is loaded on the top of the antenna.By optimizing the size and height of the metasurface,the bandwidth of the antenna is expanded by 0.3GHz compared with the original antenna,and the average gain of the antenna is improved nearly2 d Bi.From the simulation and measurement results,the antenna optimized by using metasurface has a higher gain and does not affect the radiation pattern of the original antenna.In the operating frequency band,the beamwidth is stable at 56°±9.5°.In addition,the coupling of the array elements in the ideal linear array is analyzed by simulation,and the loading of the metasurface cladding also improves the port isolation of the antenna to a certain extent.2.Starting from the cross-type structure,a cross-type metasurface with the hollow double rings is designed directionally.By increasing the effective electrical length of the metal patch unit on the metasurface,the working frequency band of the metasurface is reduced,and it has effective reflection and transmission characteristics in the operating band of the antenna.The characteristics of the metasurface are analyzed from the physical point of view by using the characteristic mode theory.The results show that the metasurface mode can not be excited in the frequency band of 1.6-4GHz,which means the performance is stable.When applied this metasurface to the dipole antenna,the gain is similar to that of a square metasurface,but the cavity height is reduced by 10 mm which achieves low-profile antenna design.3.A dual-polarized dipole antenna with an open coupling gap is designed.Antenna fed by a coupling probe which is easily to adjust the impedance matching of the antenna,with a 100×100mm flat reflector plate at the bottom.Before the optimization of the antenna,the working frequency band is 1.7-3GHz and the gain is 6.7-7.8d Bi.Due to the small size of the reflector,the half-power beamwidth of the antenna fluctuates greatly in the working frequency band.The cross-type metasurface is used as the antenna cladding to form a Fabry-Perot cavity.By optimizing the height of the metasurface cladding,the antenna achieves a full operating bandwidth of 1.7-3.8GHz,and the gain can be maintained at 8.6-9.9d Bi in the 1.7-3.1GHz band.By the way,the beamwidth of-3d B in the horizontal plane is stable at 63.5°±6.6°.Compared with the original antenna,the beamwidth is narrowed and the directivity of the antenna is enhanced.The loading of the metasurface enables the antenna to obtain good working performance with smaller size compared with other dualpolarized antennas.The design of the two sets dipole antennas optimized by metasurface meets the requirements of the direction finding system and the base station system communication with the advantages of broadband,high gain,and high cross-polarization ratio.Therefore,the optimized way to construct resonant cavity antennas by adding metasurface cladding has important reference significance in the design of high gain antenna.