Research On Early-/Late-time Responses And Translational Motion Compensation Technique Of Midcourse Targets In Low Frequency Radar

The key to the ballistic missile defense system is to solve the problem of detection and identification of the warhead and decoy.The midcourse of the ballistic missile becomes the best period for target recognition and interception because of its long flight time.Currently,X band radar is the mainly equipment in national missile defense system(NMD)in USA.Compare to X band radar,low frequency radar can detect longer distance.The recognition time of ballistic missile can be improved by nearly 20 minutes while using low frequency radar to realize the characteristics inversion of the midcourse targets.This paper focuses on the characteristics inversion problem of the low frequency radar target in the midcourse,the effective pole extraction method is proposed based on the analysis of target scattering characteristics in resonance region.Then,the early-/late-time responses model is established,which illustrates the relationship between the early-/late-time responses as well as the physical base of the micro Doppler modulation in low frequency radar.Meanwhile,effective compensation techniques are proposed to eliminate the influence of the ionospheric effect and the high speed translation in target micro motion parameters estimation and narrow band imaging.The main works of this paper are as follows:The first chapter introduces the background and the significance of the research.Firstly,the main methods to study the characteristics of midcourse target are summarized.Secondly,the research status at home and abroad and existing problems of feature extraction in micro motion target,narrowband radar imaging technology are detailed analyzed.In the second chapter,the scattering characteristics of the target in the resonant region are studied,and the early-/late-time responses characteristics are extracted.Firstly,the basic concept of RCS is introduced,and the characteristics of RCS in Rayleigh region,resonant region and optical region are analyzed.And the electromagnetic computation method of CST Microwave studio is also presented.Then,the early-/late-time characteristics of the precession target in the resonant region are analyzed,and the improved matrix beam method is used to extract the poles in the late-tine response.The simulation results show the effectiveness of the extraction method.Finally,the transient response of the target is modeled by the response parameters acquired in the simulation experiment,and the experimental verification of micro Doppler extraction is completed.In the third chapter,a translational motion compensation algorithm based on target trajectory information is proposed.Firstly,the two body orbit model and the micro-motion radar observation model of the target are established.Secondly,we use the target orbit parameters to do the coarse compensation on the translational motion,and then the residual translation is compensated by multiple conjugate symmetric phase multiplication.Finally,the accuracy of the translational motion compensation method is analyzed by simulation experiment,which proves the validity of the proposed method.Compared with the translational compensation method based on micro-Doppler peak information extraction method,the proposed method in this paper has higher calculation accuracy and more stable performance.In the fourth chapter,an ionospheric effect correction method based on multi-carrier frequencies modulation is proposed.First,we describes the basic concepts of the ionosphere and establish the corresponding phase advance equation.Secondly,we make use of the multi-carrier radar echoes which have been compensated in chapter three to conduct phase extraction.And then we use the extracted phase to figure out the expressions of the fretting delay and ionospheric delay.Finally,the root mean square errors of the fretting parameter and the ionospheric parameter are analyzed by simulation experiment to prove the validity of the proposed method.Compare with the ionospheric correction method based on SAR imaging,the square error of the ionospheric parameters estimated by this method is much smaller,and the estimation result is better.The fifth chapter is a conclusion and prospect of the whole paper,which summarizes the main work and innovation points of this paper.The development trend of midcourse target characteristics in low frequency radar are discussed.And we need to study in the actual process to solve the separation and extraction problem of the early-/late-time responses.