| Radar detection technology is an extremely important part in modern military warfare.Because of the ability to flexibly control the amplitude,phase and polarization of electromagnetic waves,electromagnetic metarsurfaces are often used as absorbing materials to reduce the radar cross section(RCS).Radar radomes based on electromagnetic metarsurfaces have attracted the attention of researchers in various countries in recent years.At present,the methods of RCS reduction based on electromagnetic metarsurfaces are mainly divided into three types: frequency selective absorber,electromagnetic phase cancellation and polarization conversion.However,they are still limited by insufficient bandwidth reduction and poor angle stability,which leads to a long distance from practical applications.Based on the research of frequency selective absorber and phase cancellation technology,this paper innovatively proposes a hybrid mechanism to achieve ultra-wideband wide-angle RCS reduction.The main research contents and innovations are as follows:(1)The equivalent circuit model of frequency selective surface structure is established,which the working principle is also analyzed in detail.The factors that limit the absorption bandwidth of single-layer FSS and affect the absorption amplitude are theoretically calculated by using Matlab.Therefore,a double-layer absorber is proposed to expand the bandwidth.(2)The relationship between the physical absorber model and the equivalent circuit is constructed,and the equivalent circuit parameters are extracted.By changing the parameters corresponding to the circuit and the model,the influence of the structure on the resonance frequency point and bandwidth is found,and the current at the resonance frequency point of the structure is also analyzed in detail.Finally,the physical structure parameters are optimized to achieve broadband and large-angle absorption,respectively.(3)The hybrid absorber and electromagnetic cancellation technology is innovatively proposed,in which the absorber structure is responsible for reducing the low frequency RCS(1.3-13 GHz),and the electromagnetic cancellation is responsible for reducing the high frequency RCS through the spatial height arrangement.The RCS reduction model of arbitrary bandwidth can be realized by theoretical calculation,which greatly saves the simulation time.The lattice structure of the absorber is arranged according to the electromagnetic cancellation principle,and the 180 ° phase cancellation between the lattices is realized by using the height difference.Through theoretical calculation,full-wave simulation and experiment,it is mutually verified that the proposed hybrid technology can achieve ultra-wideband and large-angle RCS reduction,with good reduction performance.(4)Two kinds of mechanically and electrically adjustable integrated array antenna structures of absorbing/transmitting are designed to realize the function of absorption within band and transmission out of band.Based on the analysis of equivalent circuit model,LC resonant circuit is introduced into the lossy layer and lossless layer,respectively.The passband is generated in the absorption band through resonance.The passband frequency is mechanically and electrically adjustable by changing the slot structure of the FSS patch and the capacitance of the loaded varactor diode.The full-wave simulation results verify the effectiveness of the absorption and transmission decoupling mechanism,indicating that the structure can realize the radiation/scattering integration frequency reconfiguration and ultra-wide band large dynamic RCS regulation. |
