条带式合成孔径雷达成像方法研究

提出准正侧视合成孔径雷达小斜视角度的校正方法和子孔径参考信号相位对齐算法．准正侧视合成孔径雷达(SAR)成像的校正方法采用正侧视的予孔径聚束算法对准正侧视SAR的实测数据进行成像，根据所成的像估计出小角度斜视角，采用校正的斜视子孔径聚束算法完成最后的成像．子孔径参考信号相位对齐算法本质是将各个子孔径参考信号的相位调整为同相，并构造新的聚束窗函数进行SAR成像．理论分析指出，在不增加采样数据的条件下，该方法能增大雷达方位向成像场景范围．计算机仿真结果证实了所提方法的正确性．     

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。     

毫米波小斜视SAR垂直航向运动分析与补偿

In millimeter wave high resolution SAR imaging, the existing squint SAR cross-track motion compensation algorithm brings into a phase error of more than π/4 during the imaging process. The phase error would worsen the compensation effect. This paper transforms the squint slant range with the motion error into the side-looking slant range. We adopt the side-looking cross-track motion compensation algorithm to cross-track motion compensation. The proposed algorithm works well on the millimeter wave real data in the 10° squint angle and the results are better than those obtained by existing algorithms in the same squint angle.     

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.     

一种精确的前斜视SAR方位高分辨分析方法

基于前斜视SAR的运动特点和波束在场景平面上的扫描规律，建立了点目标与天线相位中心的瞬时斜距模型，提出了一种新的关于前斜SAR方位向高分辨特征分析的方法，通过对前斜视SAR合成孔径长度及方位分辨特性的研究，给出了合成孔径长度与方位分辨率近似公式的使用条件并作为前斜视SAR较为精确地成像与合理简化数据处理的基本依据．     

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．     

Imaging method for highly squinted SAR with spatially-variant doppler centroid correction

In the high squint SAR imaging, the linear range walk correction (LRWC) is usually adopted to mitigate the coupling between range and azimuth. The conventional algorithms only consider the effects of Doppler frequency modulation rate dependence but ignore the spatially-variant Doppler centroid; this will affect the final focusing. In this paper, the effects of spatially-variant Doppler centroid in high-squint synthetic aperture radar (SAR) are analyzed and discussed, and a modified nonlinear chirp scaling algorithm with spatially-variant Doppler centroid correction in high squint SAR azimuth processing is proposed in order to improve the quality of the final focusing. Both simulation and real data processing validate the effectiveness of the proposed method.     

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．     

一种新的大斜视TOPS SAR全孔径成像方法

针对大斜视模式导致回波信号距离向和方位向耦合严重,循序扫描地形观测模式波束指向的变化导致全孔径回波信号的方位带宽大于系统脉冲重复频率,引起方位谱模糊的问题,提出了一种基于修正距离徙动算法和方位谱分析的全孔径成像算法.对于全孔径数据,首先通过方位预处理获取信号无模糊的二维频谱,然后采用修正距离徙动算法进行距离徙动校正,最后通过谱分析技术和方位去斜技术将信号聚焦在方位频域.仿真实验和实测数据结果验证了该算法的有效性.     

高超声速飞行器成像算法

高超声速飞行器是目前各国航空航天发展的重点．搭载其上的合成孔径雷达成像系统面临两方面的问题：一个是多普勒与快时间的耦合,另一个是斜视成像的校正问题．借鉴调频连续波合成孔径雷达的几何模型,提出了一种去耦合的扩展的频域变标成像算法,可在一定的斜视角下解耦合并且无失真高精度成像．