Research On The Scattering Characteristics Of Periodic Structures In Time And Frequency Domains

Radar stealth technology is an important factor in Modern Warfare.Radar cross section(RCS)is the key of radar stealth technology.The study of scattering characteristics in time and frequency domain contributions to RCS reduction effectively thus enhanced stealth performance and low RCS targets detection can be achieved.The paper aims to study scattering characteristics of periodic structures in time and frequency domain.The scattering mechanism of periodic structures is revealed by analyzing the scattering characteristics of periodic structures.Structures' periodicity is used to reduce RCS of objects.Meanwhile,it is used to detect low RCS targets that the scattering in time domain from periodic structures with the time domain electromagnetic effect.This work provides a new way to improve radar stealth technology and radar anti-stealth technology.The main innovative works of this paper have the following several aspects:1.The time domain electromagnetic effect from low RCS periodic structures is studied by analyzing the time domain backward scattering of a Gaussian modulated sine wave.The effect is that the scattering wave has a large amplitude at the beginning and becomes smaller after a period of time.The mechanism of the time domain sputtering effect is revealed by analyzing the reflection and transmission currents of the equivalent circuit analysis.It is mainly due to the unbalance between the equivalent circuit capacitance and inductance at the beginning.If the equivalent circuit capacitance is increased,the time domain sputtering is more obvious.As verification,the time domain sputtering effect of slot arrays with different sizes is measured.The measured results are matching well with the theoretical analysis results.2.The scattering characteristics of the micro-strip antenna with the electromagnetic band gap(EBG)structures and low RCS chessboard surfaces with EBG structures are studied.It is revealed that the low RCS characteristic in band is mainly caused by the cancelling between the EBG structures and the metal part of the target itself.On this basis,the time domain electromagnetic effect from low RCS periodic structures is studied by analyzing the time domain backward scattering with Gaussian modulated sine wave.And it is verified by the measurement.The time domain sputtering is possible to explore a new method of detecting low RCS targets.3.A method of designing low edge scattering anisotropic high impedance surface with different refractive index in different directions is proposed.Metal patches with different rotation angles are used to product the equivalent anisotropic unit cell.The proposed surface can guide the surface wave propagates toward or away from edges of surface to avoid currents excited from the edges.The measured results match well with the theoretical design.4.The polarization independence gradient index surface is proposed using the ring-shaped patch to achieve low RCS with arbitrary polarized waves.Based on the generalized refractive index principle,square patches and Jerusalem patch type gradient index surfaces have been designed.In further studies,the results show that the square type of gradient index surface can transform the incident wave into the surface waves and the Jerusalem patch type of the gradient index surface can reduce the backward RCS in the wide frequency band.5.A polarization independence low RCS meta-surface and a wide frequency band low RCS meta-surface are designed by the coding idea.Those two meta-surfaces can scatter the incident waves into many directions and even the scattering energy to reduce the backward RCS.6.The design method of low backward RCS and even scattering in far field meta-surfaces are proposed.Firstly,E-field distribution on the sur faces is represented by approximated equations.The parameters in the equations are optimized to make the scattering meeting the design requirements.After that,according to the equations parameters,the phase distribution of the E-field on the surface is calculated.Finally,the unit cells in the corresponding position is calculated by the phase distribution.