| Cone-shaped spatial target recognition is an import part in the national aerospace defense system and radar,as eyes of aerospace defense system,also plays a significant role in cone-shaped spatial target recognition.The distance resolution performance of widebrand radar is superior to that of narrowbrand radar.Additionally,wide brand radar can not only find the interesting target among multiple targets,but also show the characteristics of the target precisely.Therefore,the modulation effect of target echoes from widebrand radar in recent years is more and more analyzed,which is determined as the key technology to the cone-shaped spatial target recognition.With the rapidly development of penetration technology and counterattacking technology,radar cross section of spatial decoy and real spatial target is growing more consistent with their infrared spectrum behavior,which results the hot analysis on the micro-motions recognition of cone-shaped spatial target.Micro-Doppler estimation is the basics of target identification using micro-motions.Based on the above background,this paper studies micro-Doppler estimation method of cone-shaped spatial target in the field of widebrand radar,mainly focusing on the kinematic and scattering characteristics of cone-shaped spatial target,the translational motion compensation of cone-shaped spatial target,micro-Doppler frequency estimation,micro-Doppler curves splitting,micro-Doppler curves reconstruction and so on.My main work on this paper is as followings:1.In order to research on the orbital motion and scattering characteristics of cone-shaped spatial target,the wide brand radar micro-Doppler model was introduced.During its mid-course flight,the cone-shaped spatial target has both translational motion characteristics and micro-motion characteristics.Firstly,this paper predicts the motion orbits of ballistic trajectory based on the translational parameters of cone-shaped target centroid.Then,common scattering center model and equivalent scattering center model were built to simulate and analyze.2.Regarding on the micro-Doppler frequency estimation of cone-shaped spatial target in wide brand radar echoes,a new analysis method of high-resolution time-frequency(SET-STIAA)was proposed,which is based on synchronization extraction transformation.SET is similar to the ridge extraction technology.Under the limited data points,the short-time Fourier transform resolution is not high enough at low points,thus,it is difficult to distinguish the close curves.It is proposed that the cooperation of adaptive algorithm at short-time iteration and synchronous extraction transformation can improve the time-frequency resolution of instantaneous frequency at low points.3.Regarding on the translational compensation and curves splitting of cone-shaped spatial target for micro-Doppler curves,a method of translational velocity compensation based on time-frequency entropy information.After obtaining clear micro-Doppler time-frequency map with the scattering center of cone-shaped spatial target,for the case only translational velocity but no translation acceleration,compensate the target translational motion by means of frequency shift and set the best compensation effects based on the difference of timefrequency entropy,utilizing micro-Doppler symmetry characteristics under the condition of complete translational compensation.When the micro-Doppler curve with complete translational compensation is obtained,for the case of scattering point with occlusion effect,a method is proposed to determine the number of scattering points according to curves' interval and then split the curves by means of nearest neighbor criteria.4.Regarding on the missing segment signal,the reconstruction algorithm without micro-Doppler curve was introduced.The instantaneous micro-Doppler curves are few-far and periodic on the time-frequency map.Factorized the periodic curves,the obtained polynomial coefficients also meet periodicity to some extent.According to the characteristic that the polynomial coefficients meet the periodicity,utilize the non-missing polynomial coefficients to restore the missing polynomial coefficients.Then,rooting the restored polynomial coefficients and get the instantaneous frequency of missing part.Finally,the complete micro-Doppler curve can be obtained which is equivalent to the original signal reconstruction. |
PDF Full Text Request