Research On Radar Cross Section Control Technology Based On Electromagnetic Metasurface

With the rapid development of radar,semiconductor and electronic information technologies,the emergence of various new radar detection systems,advanced signal tracking devices and precision-guided weapons constitutes a serious threat to the operability and survivability of targets in the modern battlefield.To enhance the combat effectiveness of the target to control the initiative in modern combat,it is necessary to investigate and apply radar stealth technology to achieve low detectability of the target.Radar stealth technology improves the battlefield strike and survivability of the target by reducing its radar cross section(RCS)to shorten the effective detection distance of enemy radar detection systems.Electromagnetic metasurfaces are two-dimensional representations of electromagnetic metamaterials,which can manipulate the amplitude,polarization and phase properties of electromagnetic waves to flexibly control the wavefront characteristics of electromagnetic waves.With the powerful electromagnetic wave control performance of the metasurface,it has a promising application in RCS management.This thesis focuses on the background that radar detection technology poses a serious threat to airborne platforms,antennas and canopies on airborne platforms are selected as research objects,aiming to resolve the problem of reconciling the radiation and scattering properties of antennas,and the optical transparency and low scattering properties of canopies using metasurface.Main research contents and contributions are summarized as follows:1.Based on the phase cancellation mechanism of the metasurface,a wideband low scattering microstrip array antenna with low Q resonators and fast optimization method is proposed in this thesis.First,the relationship between Q value and phase shift of the element is analyzed to reveal that wideband control of electromagnetic waves can be achieved employing low Q resonators.In addition,the fast optimization method based on the convolution theorem is proposed to achieve the efficient optimization of the coding matrix.Then,two kinds of low Q resonators with 180°±37° reflection phase difference in the wideband are designed and the coding metasurface is constructed.Finally,the coding metasurface is integrated with the linearly-polarized microstrip array antenna to realize the wideband low scattering microstrip array antenna.Depending on the diffusion function of the coding metasurface,the proposed low scattering microstrip array antenna realizes wideband low scattering characteristic while maintaining stable radiation properties,which achieves the incorporated radiation/scattering design of linearly-polarized microstrip array antenna and has critical applications in antenna systems for low scattering platforms.2.Relying on the polarization conversion mechanism of the metasurface,two low scattering circularly-polarized antennas based on polarization conversion metasurfaces are proposed in this thesis.First,two different reflection-type polarization converters are designed.Then,the two low scattering metasurfaces are constructed by arranging the polarization converters and their mirror structures in the chessboard layout.Finally,the two low scattering metasurfaces are integrated with the circularly-polarized microstrip antenna and circularly-polarized slot antenna to complete the two low scattering circularly-polarized antennas.With the inherent property that the polarization converter and its mirror structure have reverse reflection phase,the mentioned two low scattering circularly-polarized antennas exhibit wideband scattering suppression performance and stable radiation performance,which realizes integrated design of radiation and scattering performance and provides a new concept to design low scattering circularly-polarized antennas.3.To break through the problem of simple scattering suppression mechanism and insufficient suppression of existing low scattering metasurfaces,this thesis provides a design strategy of low scattering metasurface based on the integration of multiple mechanisms,and constructed a low scattering slot array antenna based on the hybrid mechanism metasurface.First,the polarization conversion absorber is achieved by loading lumped resistors in the polarization conversion structure to achieve the incorporation of absorption and polarization conversion mechanisms.Then,the hybrid mechanism metasurface combining absorption,polarization conversion and phase cancellation mechanisms is obtained by distributing the polarization conversion absorber and its mirror structure in the chessboard layout.Finally,the linearlypolarized slot antenna is designed and incorporated with the metasurface to establish the low scattering slot antenna with compatible radiation and scattering characteristics.This hybrid mechanism strategy enriches the design freedom of low scattering metasurfaces by fusing three different scattering suppression mechanisms,providing a new method for their future development.4.To satisfy the realistic demand that the canopy of the low scattering platform requires both optical transparency and low scattering property,an optically transparent hybrid mechanism metasurface with wideband low scattering characteristic is implemented in this thesis.The transparent polyethylene terephthalate(PET)substrates and indium tin oxide(ITO)films are selected as the materials to construct the optically transparent metasurface.The ITO film is patterned as the polarization conversion structure by laser etching technology and attached to the PET substrate,making the polarization conversion absorber to have both absorption and polarization conversion performance while maintaining optical transparency.Similarly,the polarization conversion absorber and its mirror structure are distributed in the chessboard layout to introduce the phase cancellation mechanism,which makes the hybrid mechanism metasurface have both optical transparency and scattering suppression performance.The proposed optically transparent hybrid mechanism metasurface breaks through the problem of narrow bandwidth and insufficient scattering suppression of existing optically transparent metasurfaces,achieving the compatibility of optical transparency and wideband scattering suppression properties and provides a new idea for the stealth design of the canopy in low scattering platforms.5.Facing the situation that targets in complex electromagnetic environments are threatened by the detection of multi-directional and multi-polarization radar waves,this thesis proposed an optically transparency hybrid mechanism coding metasurface with wideband low scattering characteristic.The transparent polarization conversion absorber fusing absorption and polarization conversion mechanisms is constructed employing PET substrates and ITO films,which enables the control of the amplitude and polarization properties of linearlypolarized waves.Besides,geometric phase concept is introduced so that the polarization conversion absorber and its mirror structure have reverse reflection phases under circularlypolarized incidences.Finally,an optically transparent hybrid mechanism coding metasurface is established by distributing the polarization conversion absorber and its mirror structure in accordance with a pseudo-random matrix.By introducing the concept of geometric phase,the hybrid mechanism coding metasurface achieves wideband scattering suppression under linearly-polarized and circularly-polarized incidences while preserving optical transparency,which expands the application scenarios of optically transparent metasurfaces.