Research On The Inversion Technology Of Ballistic Mid-course Targets Based On The Narrowband Radar Information

This paper aims at analyzing the recognition and inversion ability of the mid-course targets from the narrowband radar observations. We deeply study some key technologies/subjects in this dissertation, including the inversion algorithm from the narrowband radar cross section (RCS), the imaging inversion algorithm from the high-resolution time-frequency spectrum of the narrowband radar signal and the tomography imaging method based on the narrowband signal. The main contributions of this dissertation are given as follows:In Chapter 2, the static and dynamic electromagnetic scattering models of mid-course targets are established and the background knowledge of the mid-course targets inversion is introduced. Firstly, we analyze the electromagnetic scattering mechanism of the targets in the optical region, and also elaborate the relationship between the radar cross section and the target physical character and radar geometry. Then we establish the warhead model with the computer-aided design (CAD) software and calculate the electromagnetic scattering data from the return signal of the all aspects of the static targets. Finally, we deduce the Doppler modulation of the spinning targets, precessional targets and the targets with both the spinning and precessional motion and confirm the application condition of the inversion method for the mid-course targets.In Chapter 3, the inversion method of the mid-course targets based on the narrowband RCS is discussed. Firstly, a cone-sphere mapping model method is proposed to inverse the length of the mid-course targets and the compensation model of the inversion result is also given. Secondly, the statistic and periodic characteristic of the RCS sequence are analyzed and a new method of estimating the precession cycle based on nonparametric statistics theory is presented. The method can solve the false period problem effectively by accumulating the results of the variation interval Kruskal-Wallis test. Finally, the simulation results verify the theoretical results.In Chapter 4, the inversion method from the transformation domain of the narrowband signal is studied. In this Chapter, we propose a new narrowband radar imaging method for the precession cone-shaped targets. The method acquires the Doppler modulation of the precession target's scattering centers with high resolution time-frequency analysis method and extracts the Doppler parameter from the result of the time-frequency analysis with general Radon transform, then reconstructs the scattering centers position in the parameter domain. The experiment results of the anechoic chamber data show the effectiveness of the method.In Chapter 5, a radar imaging theory based on tomography is studied. We concentrate on establishing the resolution system of this radar imaging theory and applying the tomography for the narrowband imaging of the mid-course targets. Firstly, the mathematical principle of the tomographic imaging is demonstrated, and then the analysis of resolution performance based on point spread function (PSF) has been deduced for arbitrary imaging parameters. As a result, the resolution theory based on tomographic theory has brought various imaging methods into a uniform theoretical frame and the resolution performance will be predicted in any radar imaging scenario in this uniform theory when the imaging parameters are the priori knowledge. Above all, we give the linear frequency modulation (LFM) signal processing flowchart when tomography imaging is used. Numerical simulation results based on the anechoic chamber data are provided to demonstrate the validity of the narrowband imaging method for the mid-course targets.In Chapter 6, the super resolution of the tomographic theory is studied. We focus on the radar imaging when the signal support domain is sparse or deficiency. Firstly, the electromagnetic mechanism of radar imaging is outlined, and then an inherent super resolution algorithm called the imaging decomposition method is proposed, which can obtain the high resolution radar images from different applications by removing the cross-disturbance owing to the resolution limitation when the imaging parameters is the prior knowledge. Numerical circumstances have been considered in the dissertation and finally the validity of this super resolution algorithm is illustrated via simulations.In Chapter 7, the translational compensation method for narrowband imaging is considered. Firstly, we analyze the influence on the narrowband imaging by target translational motion. Then, the condition for the distance compensation and the velocity compensation has been deduced, and the conclusion that the velocity compensation is the appropriate method for the motion compensation in the narrowband imaging has been given. As the precession motion of mid-course targets will cause the chaos of the signal phase, we propose a new radar signal processing flowing for the narrowband radar motion compensation based on Doppler accurate estimation, which can estimate the accurate translational motion parameters of the mid-course targets from the real signal phase, and can realized the narrowband imaging for the mid-course targets. Finally, the theoretic analysis and experiment results show the effectiveness of this method.