前视扫描SAR超分辨成像

提出了一种前视SAR超分辨成像算法.方位维分辨通过安置线性阵列,采用"多发多收"的工作方式,通过波束形成技术得到较窄的发射波束以覆盖有限观测场景,利用目标的稀疏先验信息建立正则化问题,然后通过求解最优化问题实现超分辨成像.该算法在有限阵列长度的条件下可以获得更优的成像结果,有效降低了系统的成本和复杂度.仿真结果验证了该文分析的正确性和算法的有效性。     

利用回波数据的高分宽测机载SAR运动误差提取方法

为实现高分辨宽测绘带SAR成像,提出一种基于回波数据的高分辨宽测绘带机载SAR运动误差提取方法,有效弥补了基于惯性测量单元/全球定位系统(INS/GPS)提取的运动误差精度低的问题.首先采用一种基于图像对比度最优的方法对SAR回波数据进行相位误差估计,然后利用加权总体最小二乘(WTLS)基于空变相位误差模型反演运动轨迹...     

脉内聚束SAR方位高分辨率宽测绘带成像

针对星载合成孔径雷达(SAR)方位高分辨与宽测绘带之间的矛盾,提出脉内聚束SAR模式实现高分辨宽测绘带成像．建立了脉内聚束SAR模型,分析了脉内聚束SAR回波信号特性,得出脉内扫描技术会导致不同方位子场景上散射点相互叠加引起距离模糊的结论．针对该距离模糊,利用俯仰维多孔径进行空域滤波解模糊;并分析了地形起伏对成像结果的影响．脉内聚束SAR利用脉内扫描获得更长的合成孔径,以此实现高的方位分辨率; 同时在采用低脉冲重复频率的情况下,获得宽测绘带,从而实现了高分辨宽测绘带成像．仿真实验结果验证了该方法的有效性．     

一种时域去走动的四阶模型SAR成像方法

针对大斜视SAR回波耦合性强问题,从提高斜距模型近似精度和距离徙动校正精度两方面对SAR成像进行了研究,推导了一种四阶SAR成像算法模型。首先为了提高模型近似度,将斜距展开到四次项,然后为了将距离向和方位向进行初步解耦,在时域进行走动补偿,通过级数反演法将信号转到二维频域进行距离弯曲校正,方位匹配滤波后得到聚焦后的SAR图像。该方法流程简单,便于实时处理。仿真结果表明,该方法具有较强斜视处理能力,取得了较高的成像分辨率。     

一种新的宽带目标识别雷达杂波抑制方法

宽带雷达相邻回波间会出现越距离单元走动现象,传统杂波抑制方法不适用．针对这一情况,提出一种在频率域-多普勒域宽带雷达杂波抑制方法．在目标速度未知时,采用改进的Hough变换将目标信息提取出来,等同于完成对杂波的抑制过程; 如果有目标速度的先验信息,则可以先进行运动补偿,然后提取目标信息,上述两种提取目标信息的途径避免了虑除杂波过程中对目标信号能量的损失．计算机仿真结果表明,该方法在输入信杂比为-10dB(速度未知)或-15dB(速度已知)的情况下仍可保持较高的识别性能,并且在输入信噪比为-5dB时,算法依然保持稳定的性能,对噪声有较好的稳健性．     

New method for azimuth-dependent correction of highly squint missile-borne SAR subaperture imaging

Squinted imaging is one of the most important modes in the missile-borne synthetic aperture radar (SAR). Usually, from the view of practical applications, the missile-borne SAR adopts subaperture processing in order to implement quick look imaging. In the highly squint mode, the echo signal couples greatly between range and azimuth, so traditional algorithms perform the linear range walk correction in the azimuth time domain firstly to mitigate greatly the range-azimuth coupling, which causes the problem of position dependent azimuth phase, resulting in the azimuth uniform processing disabled and impacting the azimuth depth of focus (DOF). Based on the deep analysis of the instantaneous slant range model in the highly squint missile-borne SAR, this paper proposes high-order phase filtering to correct azimuth-dependence for implementing the identical azimuth-focusing processing. Simulation results validate the effectiveness of the proposed algorithm.     

Detection of oil spills in a complex scene of SAR imagery

We present a method for detecting oil spills in a complex scene of SAR imagery,including segmenting oil spills,and avoiding false alarms.Segmentation is carried out using a multi-time and multi-hierarchical method by dividing the complex sea surface into bright sea and dark sea.Gray-based and edge-based segmentations are done to extract oil spills from bright and dark sea,respectively.The proposed method can extract complete oil spills,obtain better visual results,and increase detection probability more accurately than the traditional method.Based on the surrounding features and the oil spills’features,dark land spots and low contrast dark spots are removed efficiently,thus reducing false alarms.The experimental results demonstrate that the proposed algorithm has fast computation speed,high detection accuracy,and is very useful and effective for detecting oil spills in SAR imagery.     

一种SAR成像快速算法及其并行实现

提出了一种新的实时合成孔径雷达成像快速算法，减少了合成孔径雷达成像中压缩处理的运算量．对任意长度的序列采用了填零-分解快速傅里叶变换方法，并优化了补零参数和分解方式，使得压缩处理算法的运算量最小化．此算法在并行多处理器上实现了合成孔径雷达实时成像，提高了成像处理速度，减少了成像迟延。     

Floating small target detection in the sea clutter via block-whitened clutter suppression

It is always a difficult task for the marine surface surveillance radar to detect the floating small target embedded in the sea clutter. Considering the non-uniform and non-stationary nature of sea clutter, the block-whitening strategy is used to suppress the clutter. By analyzing the differences between the energy distributions of the clutter-only returns and those of the returns with the target in the time-frequency (TF) plane, a TF feature is extracted via the TF-ridge-aided Hough transform. A detector using the TF feature is proposed. Experimental results for the IPIX radar datasets show that the proposed detector attains a better detection performance than the fractal-based detector in a relatively short observation time.     

Imaging method for the extended scene of missile-borne bistatic forward-looking SAR

Due to such problems as high order terms in double square roots and more serious range cell migration than monostatic or bistatic SAR in range history, caused by high velocities and accelerations in both the transmitter and the receiver platforms in a new and special bistatic synthetic aperture radar imaging mode, i.e., missile-borne bistatic forward-looking synthetic aperture radar, an imaging algorithm correcting space variance for the extended scene for is proposed. The range walk is firstly corrected in the time domain to reduce the two dimensional (2D) coupling. And then the space variance of phase terms, in the 2D frequency spectrum of the echo signal with high precision gained by the method of series reversion, is analyzed quantitatively. The imaging is completed through polynomial fitting and variant match filter designing. With simple operation and less computation, our algorithm is convenient for imaging processing and subsequent procedure in the missile-borne platform. Simulation results show our imaging method significantly corrects the space variance, improves the focus quality of fringe targets, and thus extends the imaging scene.     

雨杂波中介质圆柱目标的极化滤波增强

在极化域中对雨介质和目标的电磁波散射特性进行了研究．得出了雨区的散射矩阵和目标的散射矩阵．在毫米波段计算了雨区的后向散射引起的雨杂波功率密度随频率及降雨率的变化．对雨杂波中的有限长的介质圆柱目标的极化滤波增强进行了数值仿真,得到了其最优化信杂比在Poincare球上对应的位置,进而给出发射、接收天线应采取的最佳极化状态．     

弹载扫描SAR宽测绘带模式成像方法研究

针对弹载SAR景象匹配制导中匹配概率较低,需要大测绘带图像的问题,提出了通过天线距离向扫描扩大测绘带宽度的弹载扫描SAR宽测绘带成像模式.建立了弹体三维运动下的成像几何模型,给出了目标斜距表达式和回波信号表达式.通过分析扫描造成的线性距离走动空变性与多普勒中心空变性的问题,提出了改进的Range-Dopp ler成像算法,并分析了算法运算量.然后推导了弹体存在侧向移动时的几何校正公式.最后通过仿真验证了所提成像模式和算法的可行性.     

舰船目标三维散射中心建模及SAR快速仿真方法

直接合成孔径雷达成像仿真方法在实现大型舰船目标回波仿真和合成孔径雷达成像时时效偏低,难以满足对海探测制导闭环验证过程中对合成孔径雷达快速生成的需求.因此,提出了基于三维散射中心的舰船目标合成孔径雷达回波和成像仿真方法.首先通过射线管积分三维快速成像和CLEAN三维散射中心提取得到不同视角下目标三维散射中心;然后通过对应...     

匀加速旋转目标ISAR成像的横向分辨率

对于机动目标,目标相对于雷达的转动在一定条件下近似为匀加速转动,运动补偿后目标各散射点回波多普勒频移可近似为线性函数．该文研究了此时逆合成孔径雷达（ＩＳＡＲ）成像的方法,讨论了横向分辨率和旋转角度的关系,并证明了在一般情况下和匀速转动时的关系是一样的     

机载大斜视SAR的快速简易成像方法

大斜视角下SAR信号特点表现为大的距离走动和小的距离弯曲,这使得采用时域距离走动校正和二维可分离成像方法成为可能．但方位场景较大时要考虑聚焦深度的限制,须采用复杂的算法．提出一种将成像和校正几何形变相结合的分段处理方法,段与段之间可以完全衔接,实现快速连续实时成像．仿真试验和实测数据成像均证明快速简易方法是可行的．     

一种高速自旋目标三维成像新算法

提出了一种基于二维频谱匹配滤波器组的高速旋转目标三维ISAR成像的算法．每个频谱匹配滤波器能输出对应散射点的聚焦切片．从各个滤波器组输出的聚焦切片提取聚焦点的三维空间参数,可以构建目标的三维像．已有的基于广义Radon 变换 (GRT) 和扩展的Hough变换 (EHT) 实现旋转目标三维空间信息提取的算法,由于是对散射点逐点进行投影,因此运算量很大,效率很低．该算法采用的是匹配滤波的处理方法,在处理过程中使用快速傅里叶变换(FFT), 使计算效率显著提高．计算机仿真验证了这种算法的正确性．     

New method for range-ambiguous clutter suppression in non-side-looking airborne radar

To suppress the seriously range-ambiguous clutter, an approach based on the frequency diverse array (FDA) technique is proposed. Based on the space-time signal model in FDA radar, the frequency increment is designed to distinguish the clutter at ambiguous ranges and avoid signal decorrelation. Then, the subspace projection algorithm is used for range-ambiguous clutter suppression. Numerical simulations show the effectiveness of the proposed method. Even when the number of the elevation degrees-of-freedom (DOFs) is limited, the proposed method performs better than the conventional elevation filtering method.     

修正的K-分布海杂波仿真模型和新的海杂波功率谱描述方法

为有效仿真时空相关海杂波和准确地描述海杂波的功率谱,提出一种基于球不变随机过程(SIRP)修正的时空相关二维K-分布海杂波仿真模型,以特征函数为桥梁给出一种新的海杂波功率谱描述方法。对生成杂波序列的时间和空间相关特性、幅度分布特性以及功率谱进行分析,并比较了常用的高斯函数模型与新的功率谱函数模型之间的差异。实验仿真和实测数据表明,修正的仿真模型是有效的,新推导的功率谱函数模型比高斯函数谱模型更能准确描述K-分布的功率谱。     

杂波环境下基于粒子滤波的雷达微弱目标TBD算法

针对杂波环境下的雷达微弱目标检测前跟踪问题,提出了 Weibull杂波分布下PF-TBD算法。该算法采用 Weibull杂波分布的量测模型,并基于粒子滤波算法,推导出似然函数和粒子权重。仿真结果表明,Weibull 杂波环境下 PF-TBD算法稳定性良好。     

Range ambiguous clutter suppression for the SAR/GMTI system based on the frequency diverse array

A range ambiguous clutter suppression approach based on frequency diverse array configuration is proposed to handle the range ambiguity of the space borne wide-swath high-resolution synthetic aperture radar ground moving target indication (SAR/GMTI) system with a high pulse repetition frequency. Since echoes from different ambiguous range regions are separable in the transmit spatial frequency domain, a filter bank is employed to extract echoes from each region, and then the transmit beam forming is implemented to suppress the clutter in each range region. Simulation results demonstrate that, by making full use of the limited channels, the proposed method could weaken the influence of heterogeneous clutter in each region and reconstruct moving target signals without range ambiguity, so as to expand the detection region evidently.