Study On Bistatic Radar Scattering Characteristics Modeling And Feature Extraction For Space Targets

With the improvement of penetration technology for the space targets,the radar as the vital sensor of space target defense(STD)system requires better performance: antistealth,anti-interference,information fusion,etc.Bistatic radar is one of the advanced radar systems with four countermeasures capabilities.Bistatic radar is urgently needed to improve the ability of early warning,tracking,and recognition of the STD system.This dissertation aims to provide state-of-the-art space target defense research using bistatic radar.Four contents are mainly studied: 1)bistatic scattering center characteristics modeling and polarization scattering characteristics modeling of space target;2)bistatic micro-Doppler parametric model and structure feature extraction;3)bistatic polarization parameters extraction and three-dimensional(3-D)attitude estimation;4)separation movement modeling and feature extraction.The proposed methods in this dissertation supplement the feature extraction algorithms of monostatic radar space targets and provide the theoretical basis for the future development of bistatic radar.The main research contents and conclusions of this dissertation are as follows.Firstly,the bistatic scattering characteristics of the space target are the basis of this dissertation,in which the scattering center characteristics and polarization scattering characteristics are investigated.Scattering center characteristics: shooting and bouncing ray method and physical optics are applied to deduce the theoretical location of coupling scattering centers in acute,right,and obtuse dihedral structures.This work is the fundament for dihedral-type structure recognition and size inversion.The theoretical location of sliding scattering centers on the streamlined space target surface(SSCS)is also derived.Then,the analytical micro-Doppler(m D)of SSCS is deduced.Based on that,the relationship between m D non-sine properties and the average line-of-sight angle is revealed.Polarization scattering characteristics:monostatic Huynen target parameters are extended to the bistatic case.Then,the physical properties of bistatic Huynen target parameters(BHTPs)are analyzed,which provides a fundamental theory for component structure recognition and 3-D attitude estimation.Secondly,the bistatic m D parametric model is established to represent the m D characteristics of three types of scattering centers.A new method that judges the scattering centers sliding or not is proposed.A scenario-definition full-polarization dynamic echo simulation method of bistatic radar is investigated to resolve the difference of polarization base definition in the radar coordinate system and electromagnetic simulation.Based on the analytical m D of local scattering center(LSC),sliding scattering center on the bottom edge(SSCE),and SSCS,the m D parametric model(m DPM)is proposed.m DPM reveals that the m D of the scattering center on the micro-motion space target can be approximated as the sum of first-order sine and second-order sine functions.Based on m DPM,a novel parameterized timefrequency method is proposed.Experimental results demonstrate that it can improve the energy concentration of m D ridges in the time-frequency distribution and resolve the discontinuity problem of m D curves.At last,a new feature sliding coefficient is defined.We also propose a quantitative method to determine whether the scattering center is sliding based on the defined sliding coefficient.Thirdly,the 3-D attitude estimation of the space target is investigated,and the bistatic full-polarization scattering measurement system is set up to validate the proposed algorithms.The change of the target behavior often brings about the change of the attitude,so the three-dimensional attitude of the target is an effective feature to reflect the target behavior.A new BHTPs extraction algorithm based on the Sinclair matrix is proposed.Compared to the Kennaugh-based conventional algorithm presented by France scientist Schnaider,the Sinclair-based algorithm is more concise and robust.A novel algorithm is proposed to estimate the 3-D attitude using bistatic full-polarization information,which has two advantages compared to conventional monostatic algorithms: 1)the proposed algorithm can realize 3-D attitude estimation with a single snapshot.2)the proposed algorithm relies on the narrowband radar measurement to avoid wideband coherent processing.A simple,flexible,and low-cost bistatic full-polarization scattering measurement system has been built that provides a platform and experimental conditions for researching the bistatic scattering characteristics.The data set of bistatic full-polarization scattering field in the X-band is obtained.Based on that,some critical algorithms proposed in this dissertation,such as BHTPs extraction algorithm and 3-D attitude estimation,have been verified.At last,the separation movement features of space targets are proposed.The definition and significance of separation movement features are discussed.Then,the movement models of three types of separation movement are established.After that,the RCS mean value,HRRP projection length,scattering center number,characterization angle,symmetry angle,and polarization divergence parameter are selected based on electromagnetic simulation results.The work provides quantitative indices to judge whether the separation movement of space targets occurs correctly.