Research And Design Of High Isolation And High Gain Antennas Based On Electromagnetic Metasurfaces

With the rapid development of communication technology,people’s requirements for antenna performance are becoming higher and higher.Traditional microstrip antennas can no longer meet people’s needs.The emergence of electromagnetic metamaterials provides a new way to improve antenna performance.By utilizing its extraordinary electromagnetic properties,the gain,bandwidth,and isolation of antennas can be improved.This paper studies the special electromagnetic properties of electromagnetic metasurfaces,designs two broadband electromagnetic wave control metasurfaces,and analyzes their electromagnetic properties using scattering parameter extraction and dispersion mode methods.Finally,the application of electromagnetic metasurfaces in array antenna decoupling and antenna gain enhancement is studied.The main contents of this paper are as follows:Firstly,the basic concept of electromagnetic metamaterials,extraordinary electromagnetic properties,and two commonly used methods for analyzing electromagnetic metasurfaces,scattering parameter extraction and dispersion mode method,are introduced.Then,a new metasurface(SRR-MS)and a magnetically negative electromagnetic metasurface(MNG-MS)are designed.The electromagnetic parameters such as magnetic permeability and dielectric constant of the metasurfaces are calculated using the scattering parameter extraction method,and the results show that both SRR-MS and MNG-MS can produce beam focusing effects.Secondly,a 1×2 microstrip antenna array with a working frequency of 2.45 GHz and a new electromagnetic bandgap(EBG)structure are designed.The coupling degree between antenna units is 19 dB.The dispersion curve of the EBG structure is extracted using the dispersion mode method.After loading the EBG structure between antenna units,surface waves on the antenna can be suppressed,and the isolation of the antenna is improved by 6dB.Using the SRR-MS unit in chapter 3 to form a coplanar negative magnetic constant medium wall,loaded between antenna units,not only changes the direction of the spatial coupling wave but also introduces new coupling paths.Direct coupling and indirect coupling cancel each other out,and the isolation between antenna units is improved by 40.7dB.Finally,a broadband high-gain antenna based on the MNG-MS is designed.By adding a slot in the center of the antenna and a feeding gap on the ground plane,a broadband antenna with a working frequency of 5.7GHz is designed.Using the MNG-MS unit in chapter 3 to form a periodic extension to form a broadband negative magnetic permeability metamaterial coating,loaded above the antenna at half a wavelength,can suppress lateral radiation.The gain of the antenna is improved in the frequency range of 4.0～7.0GHz,and the gain of the antenna with the loaded metamaterial coating is 11.6dB,which is 2dB higher than the original antenna.By studying the relevant theories of metamaterials and antennas,this paper designs two broadband electromagnetic wave control metasurfaces.Then,the electromagnetic metasurfaces are jointly designed with antennas.The results show that compared with the original antenna,the gain and isolation of the antenna with the loaded electromagnetic metasurface are significantly improved.