Research On RCS Reduction Technology Based On Polarization Conversion

With the rapid development of modern electronic information technology,it is imminent to improve the stealth performance of various military weapons and equipment.Radar Cross Section(RCS),as a physical quantity to measure stealth performance,characterizes the enemy's radar's ability to detect its own targets.The methods to achieve RCS reduction mainly include changing the target shape,loading absorbing materials,and loading passive or active impedance.Metamaterials are commonly used,and they are widely used in many fields due to their unique electromagnetic control characteristics.The polarization conversion metasurface,as a metamaterial that can control the polarization of electromagnetic waves,has the advantages of lightness,thinness,and low profile,and has high application value.At present,RCS reduction based on polarization conversion is mainly concentrated in the case of normal incidence of electromagnetic waves,and there are few studies on the condition of large-angle oblique incidence,and the effect is not obvious.In actual situations,the oblique incidence of electromagnetic waves is common.Therefore,it is worthy of in-depth study for the broadband,wide-angle RCS reduced polarization conversion metasurface.This paper takes the artificial surface based on the polarization conversion as the research goal,carries out the design of the reflection-type polarization conversion artificial structure in the microwave frequency band,and carries out a series of work such as optimization design and experimental verification,and achieves broadband,wide-angle and high-efficiency polarization.Conversion structure,taking the designed polarization conversion structure as the basic unit of RCS reduction structure,carry out RCS reduction structure design,analyze its RCS reduction physical mechanism and carry out corresponding experimental verification work.The main research contents of this paper are as follows:(1)The RCS reduction metasurface based on the stepped polarization conversion unit structure is proposed.The unit structure can maintain a bandwidth of 6.68 GHz with a cross-polarization reflection coefficient> 0.75 under an oblique incidence of60 °.When electromagnetic waves are incident perpendicularly to the chessboard metasurface composed of it,the RCS reduction bandwidth of more than 10 dB is6.9-16.5 GHz.At the operating frequency points of 8.094 GHz and 14.208 GHz,its single-site RCS has a good reduction effect in the range of ± 60 ° and ± 28 °,respectively.The composite metasurface combining polarization conversion and phase gradient scans the size parameters of the pattern layer in the unit structure to obtain 6unit structures with a reflection phase difference of 60° and a coverage area of 360°.The six unit structures are arranged periodically and symmetrically into a composite metasurface,which has a good RCS reduction effect under the conditions of vertical incidence and oblique incidence of the x and y polarized waves.At 11.69 GHz,the y polarized wave There is a good RCS reduction effect in the angle range of 75 ° at oblique incidence.(2)A chessboard metasurface based on the hexagonal split ring polarization conversion unit structure is proposed.The bandwidth range of the basic hexagonal split ring structure with cross-polarization reflection coefficient> 0.8 is 6.5 GHz-15.4 GHz,and the reduced bandwidth of the metasurface above 5dB is 11.6 GHz,and the maximum reduction peak is at 10.5 GHz.The shrinkage is up to 25.1 dB.Through deformation,a dual-band polarization conversion structure is obtained.The reduced bandwidth range of the metasurface composed of it above 5 dB is 10.8 GHz,the maximum reduction peak is at 16 GHz,and the reduction is 29.8 dB.(3)A chessboard metasurface based on the double-layer rectangular ring polarization conversion unit structure is proposed.This unit structure is a dual-band polarization conversion unit,and its cross-polarization reflection coefficient> 0.9 has a bandwidth range of 8.1 GHz.Analyze the influence of the change of the thickness of the upper and lower layers on the polarization conversion of the unit structure.When the thickness of the lower layer is unchanged,as the thickness of the upper layer increases,its working frequency point and the dual-band boundary point move to the low frequency,and the bandwidth decreases;when the thickness of the upper layer does not change At this time,as the thickness of the lower layer increases,the polarization conversion efficiency and bandwidth become lower,but the dual-band boundary point remains unchanged.The RCS of the metasurface composed of the basic unit structure reduces the bandwidth by more than 5 dB to 10.5 GHz,the reduction peak is at 9.5 GHz,and the reduction is 32.5 dB.