天基SAR抗干扰与空间目标精确成像方法研究
发布时间：2018-11-29 08:28
【摘要】：天基监视雷达是陆-海-空-天一体化战略预警监视系统的重要组成部分,基于合成孔径雷达(SAR)成像、逆合成孔径雷达(ISAR)成像以及动目标显示等多种技术手段和工作模式,同时具备监视地面、海面目标以及空间目标的能力。天基监视雷达搭载的观测平台运行于外部空间轨道,可以通过观测高度的提升突破地球曲率的影响,同时凭借其较强的抗摧毁能力自由进出敌方控制区域,实现对全球任何热点地区的连续监视并提供充足的战略防御监视时间,因而具备全天时、全天候和全球覆盖等优点,可有效弥补地基、海基和机载监视雷达的局限性和不足,在军事和民用领域均得到了广泛应用。天基监视雷达系统可分为对地监视模式和空间监视模式。对地监视模式中,天基监视雷达指向区域的电磁环境相对较为复杂,包含非蓄意干扰和电子对抗中人为施放的各种窄带干扰和宽带干扰,由于天基监视雷达发射信号的宽带特性,使得对地监视模式极易受到各类干扰源辐射信号的影响;空间监视模式中,由于星载雷达发射功率孔径积受限,且观测空间目标的作用距离往往较远(几百公里~几千公里),使得星载ISAR成像系统的回波信噪比降低,导致包络对齐结果中出现明显的突跳误差和积累误差,并最终影响ISAR成像质量,为后续的图像判读及目标识别带来障碍。本论文紧密围绕天基监视雷达系统对地监视模式和空间监视模式对各类目标实施监视过程中的实际问题,针对复杂电磁环境下的SAR干扰抑制及低信噪比条件下的ISAR包络对齐方法等关键技术进行深入研究。主要工作和贡献为:1、对天基监视雷达涉及的工作模式进行了介绍,分析了各类工作模式的特点;以条带模式正侧视情况为例,分析了对地监视模式的回波信号基本模型;研究了天基监视雷达系统对地监视模式可能面临的干扰类型及其信号形式和基本特点;结合天基监视雷达的特点和任务要求,给出空间监视模式工作模式总体方案设想;以直线运动模型为例,给出空间监视模式的回波信号基本模型,并结合散射点斜距方程展开式详细分析了天基ISAR面临的主要问题及其产生原因。2、基于时变窄带干扰信号模型,在充分考虑窄带干扰信号时变特性的基础上对时变窄带干扰抑制问题展开深入研究,针对时变窄带干扰条件下传统窄带干扰抑制方法性能下降问题,提出一种基于迭代自适应方法的时变窄带干扰抑制方法。该方法无需进行参数搜索和模型定阶,可以利用少量训练样本自适应迭代估计窄带干扰信号频谱,并采用子空间投影方法对干扰信号进行滤除。仿真结果表明所提方法能够有效抑制窄带干扰,并复原被遮盖有用信号、重现SAR图像细节信息,从而大幅改善时变窄带干扰影响下的SAR成像质量,具有良好的干扰抑制性能。3、基于天基监视雷达宽带非蓄意干扰的时频聚集性,针对传统时频滤波方法频率分辨率受限所导致的宽带干扰抑制性能下降问题,提出一种SAR宽带非蓄意干扰抑制方法。该方法无需进行参数搜索和模型定阶,可以在短时傅里叶变换分析窗函数对应的小时宽范围内,利用少量观测数据自适应迭代估计宽带干扰信号瞬时频率,并采用子空间投影方法对干扰信号进行滤除,同时,还可获得高分辨率且无交叉项的线性时频分析结果。仿真分析表明所提方法能够有效抑制宽带干扰且有用信号损失较小,可以大幅改善宽带干扰影响下的SAR成像质量,具有良好的干扰抑制性能。4、针对低信噪比条件下传统包络对齐算法性能下降问题,提出基于迭代加权最小二乘拟合的ISAR包络对齐方法(Iterative Cleaning and Weighted Least Squares,ICWLS)。该方法利用目标的平稳运动特性,对目标走动量和加权矩阵采用迭代交替更新方式,在估计出目标运动参数的基础上实现包络对齐。上述方法基于数据惩罚构造加权矩阵且采用对角形式,可显著提高包络对齐精度,但加权矩阵的估计尚未达到统计最优。因此考虑根据包络对齐误差统计参数构造最优加权矩阵并进行迭代更新,提出一种迭代的最优加权拟合包络对齐方法(Iterative Optimized Weighted Fitting,IOWF),以期进一步优化ICWLS方法包络对齐性能。仿真结果表明所提方法能有效抑制突跳误差的传播和缓解积累误差所导致的参数估计精度下降问题,具有良好的包络对齐性能。
[Abstract]:The space-based surveillance radar is an important part of the land-sea-air-day integrated strategy early-warning monitoring system, and is based on various technical means and working modes such as synthetic aperture radar (SAR) imaging, inverse synthetic aperture radar (ISAR) imaging and moving target display, The capabilities of the sea and space targets. the observation platform mounted by the space-based monitoring radar is operated on an external space track, can break through the influence of the curvature of the earth by observing the elevation of the height, the continuous monitoring of any hot spot area in the world is realized and sufficient strategic defense monitoring time is provided, so that the invention has the advantages of all-day, all-weather and global coverage and the like, and can effectively make up the limitation and the defect of the foundation, the sea base and the on-board monitoring radar, It has been widely used in the military and civil fields. The space-based surveillance radar system can be divided into a local monitoring mode and a space monitoring mode. in the ground monitoring mode, the electromagnetic environment of the space-based monitoring radar pointing area is relatively complex, so that the ground monitoring mode is very easy to be influenced by various interference source radiation signals; in the space monitoring mode, because the star-borne radar transmission power aperture area is limited, and the action distance of the observation space target is often far from (several hundred kilometers to several thousand kilometers), so that the echo signal-to-noise ratio of the star-borne ISAR imaging system is reduced, the obvious process-jump error and the accumulation error in the envelope alignment result are caused, and finally the ISAR imaging quality is influenced, and the obstacle is brought for subsequent image interpretation and target recognition. In this paper, the real problems of the space-based surveillance radar system in the monitoring process of various targets are closely studied, and the key technologies such as the SAR interference suppression and the ISAR envelope alignment method under the condition of low signal-to-noise ratio are deeply studied. The main work and contribution are: 1. The work mode involved in space-based surveillance radar is introduced, the characteristics of various working modes are analyzed, and the basic model of the echo signals of the ground monitoring mode is analyzed in the case of the positive side view of the strip mode. This paper studies the type of interference that the space-based surveillance radar system may face in the ground monitoring mode and its signal form and basic characteristics. In combination with the characteristics and task requirements of the space-based surveillance radar, the general scheme of the working mode of the space monitoring mode is given. The linear motion model is an example. in this paper, the basic model of the echo signal of the space monitoring mode is given, and the main problems and the causes of the space-based ISAR are analyzed in detail with the expansion of the oblique distance equation of the scattering point. On the basis of fully considering the time-varying characteristics of the narrow-band interference signal, the problem of the interference suppression of the narrow-band interference in the time-span is studied. In the light of the problem of the performance degradation of the conventional narrow-band interference suppression method under the condition of the narrow-band interference, a method for suppressing the interference of the narrow-band interference in the time of the iterative adaptive method is proposed. in that method, a parameter search and a model order are not needed, a small amount of training sample can be used to adaptively and iteratively estimate the narrow-band interference signal spectrum, and a subspace projection method is adopted to filter the interference signal. The simulation results show that the proposed method can effectively suppress the narrow-band interference and recover the masked useful signal to reproduce the SAR image detail information, thereby greatly improving the SAR imaging quality under the influence of the narrow-band interference when the narrow-band interference is greatly improved, and has good interference rejection performance. Based on the time-frequency aggregation of the wideband non-intentional interference of the space-based surveillance radar, the problem of the performance of the wideband interference suppression caused by the limited frequency resolution of the conventional time-frequency filtering method is a problem, and a method for suppressing the SAR wideband non-intentional interference is proposed. the method does not need to perform parameter search and model order, can estimate the instantaneous frequency of the broadband interference signal by using a small amount of observation data in an hour wide range corresponding to the short-time Fourier transform analysis window function, and filter the interference signal by adopting a subspace projection method, At the same time, a linear time-frequency analysis result of high resolution and no cross term can be obtained. The simulation analysis shows that the proposed method can effectively suppress the broadband interference and the signal loss is small, can greatly improve the SAR imaging quality under the influence of the broadband interference, and has good interference rejection performance. An ISAR envelope alignment method based on iterative weighted least squares fitting (ICWLS) is proposed. The method utilizes the stationary motion characteristics of the target, adopts an iterative and alternating updating method to the target walking momentum and the weighting matrix, and realizes the envelope alignment on the basis of estimating the target motion parameters. in that method, the weight matrix is construct based on the data penalty, and the diagonal form is adopted, so that the envelope alignment precision can be obviously improved, but the estimation of the weight matrix has not reached the statistical optimal. Considering that the optimal weighting matrix is constructed according to the statistical parameters of the envelope alignment error and the iterative updating is carried out, an iterative optimal weighted fitting envelope alignment method (IWF) is proposed, with a view to further optimizing the envelope alignment performance of the ICWLS method. The simulation results show that the proposed method can effectively suppress the propagation of the process-jump error and reduce the estimation precision of the parameter estimation caused by the accumulation error, and has good envelope alignment performance.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.52
本文编号：2364501
[Abstract]:The space-based surveillance radar is an important part of the land-sea-air-day integrated strategy early-warning monitoring system, and is based on various technical means and working modes such as synthetic aperture radar (SAR) imaging, inverse synthetic aperture radar (ISAR) imaging and moving target display, The capabilities of the sea and space targets. the observation platform mounted by the space-based monitoring radar is operated on an external space track, can break through the influence of the curvature of the earth by observing the elevation of the height, the continuous monitoring of any hot spot area in the world is realized and sufficient strategic defense monitoring time is provided, so that the invention has the advantages of all-day, all-weather and global coverage and the like, and can effectively make up the limitation and the defect of the foundation, the sea base and the on-board monitoring radar, It has been widely used in the military and civil fields. The space-based surveillance radar system can be divided into a local monitoring mode and a space monitoring mode. in the ground monitoring mode, the electromagnetic environment of the space-based monitoring radar pointing area is relatively complex, so that the ground monitoring mode is very easy to be influenced by various interference source radiation signals; in the space monitoring mode, because the star-borne radar transmission power aperture area is limited, and the action distance of the observation space target is often far from (several hundred kilometers to several thousand kilometers), so that the echo signal-to-noise ratio of the star-borne ISAR imaging system is reduced, the obvious process-jump error and the accumulation error in the envelope alignment result are caused, and finally the ISAR imaging quality is influenced, and the obstacle is brought for subsequent image interpretation and target recognition. In this paper, the real problems of the space-based surveillance radar system in the monitoring process of various targets are closely studied, and the key technologies such as the SAR interference suppression and the ISAR envelope alignment method under the condition of low signal-to-noise ratio are deeply studied. The main work and contribution are: 1. The work mode involved in space-based surveillance radar is introduced, the characteristics of various working modes are analyzed, and the basic model of the echo signals of the ground monitoring mode is analyzed in the case of the positive side view of the strip mode. This paper studies the type of interference that the space-based surveillance radar system may face in the ground monitoring mode and its signal form and basic characteristics. In combination with the characteristics and task requirements of the space-based surveillance radar, the general scheme of the working mode of the space monitoring mode is given. The linear motion model is an example. in this paper, the basic model of the echo signal of the space monitoring mode is given, and the main problems and the causes of the space-based ISAR are analyzed in detail with the expansion of the oblique distance equation of the scattering point. On the basis of fully considering the time-varying characteristics of the narrow-band interference signal, the problem of the interference suppression of the narrow-band interference in the time-span is studied. In the light of the problem of the performance degradation of the conventional narrow-band interference suppression method under the condition of the narrow-band interference, a method for suppressing the interference of the narrow-band interference in the time of the iterative adaptive method is proposed. in that method, a parameter search and a model order are not needed, a small amount of training sample can be used to adaptively and iteratively estimate the narrow-band interference signal spectrum, and a subspace projection method is adopted to filter the interference signal. The simulation results show that the proposed method can effectively suppress the narrow-band interference and recover the masked useful signal to reproduce the SAR image detail information, thereby greatly improving the SAR imaging quality under the influence of the narrow-band interference when the narrow-band interference is greatly improved, and has good interference rejection performance. Based on the time-frequency aggregation of the wideband non-intentional interference of the space-based surveillance radar, the problem of the performance of the wideband interference suppression caused by the limited frequency resolution of the conventional time-frequency filtering method is a problem, and a method for suppressing the SAR wideband non-intentional interference is proposed. the method does not need to perform parameter search and model order, can estimate the instantaneous frequency of the broadband interference signal by using a small amount of observation data in an hour wide range corresponding to the short-time Fourier transform analysis window function, and filter the interference signal by adopting a subspace projection method, At the same time, a linear time-frequency analysis result of high resolution and no cross term can be obtained. The simulation analysis shows that the proposed method can effectively suppress the broadband interference and the signal loss is small, can greatly improve the SAR imaging quality under the influence of the broadband interference, and has good interference rejection performance. An ISAR envelope alignment method based on iterative weighted least squares fitting (ICWLS) is proposed. The method utilizes the stationary motion characteristics of the target, adopts an iterative and alternating updating method to the target walking momentum and the weighting matrix, and realizes the envelope alignment on the basis of estimating the target motion parameters. in that method, the weight matrix is construct based on the data penalty, and the diagonal form is adopted, so that the envelope alignment precision can be obviously improved, but the estimation of the weight matrix has not reached the statistical optimal. Considering that the optimal weighting matrix is constructed according to the statistical parameters of the envelope alignment error and the iterative updating is carried out, an iterative optimal weighted fitting envelope alignment method (IWF) is proposed, with a view to further optimizing the envelope alignment performance of the ICWLS method. The simulation results show that the proposed method can effectively suppress the propagation of the process-jump error and reduce the estimation precision of the parameter estimation caused by the accumulation error, and has good envelope alignment performance.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN957.52
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