星-弹双基SAR建模及成像特性分析

Analysis of Space-Missile Borne Bistatic SAR Modeling and Imaging Characteristics

针对星-弹双基合成孔径雷达(SMB-BiSAR)这一特殊成像结构,根据卫星-导弹的空间几何模型,对收发平台的成像模型进行矢量描述,得到目标的距离历程以及回波信号模型。然后,利用距离等值线与多普勒等值线的正交关系,对接收站的飞行路径约束条件进行分析,并根据距离分辨率和多普勒分辨率与两者梯度的关系,得到SMB-BiSAR空间分辨率的计算公式。仿真实验表明:通过合理地规划导弹的飞行路径,SMB-BiSAR具备对目标区域的大前斜和前视高分辨成像的能力,并且其空间分辨率受双基几何构型影响较大。发射站和接收站位置夹角越大,距离分辨的效果越差;当二者位置重合时即单基模式,距离分辨率效果最佳。而发射站和接收站运动方向的夹角越大,方位分辨率越差。当二者运动方向相同时,方位分辨率效果最佳。

As a special bistatic configuration,the imaging model of space-missile borne bistatic synthetic aperture radar(SMB-BiSAR)is firstly constructed in vector according to the geometry of satellite and missile the range history and the echo signal model being obtained.Then,the constraint of the missile flight path is analyzed based on the orthogonality of iso-range and iso-Doppler contours.Finally,the spatial resolution expression of SMB-BiSAR is derived by the gradient of range history and Doppler frequency.The simulations show that SMB-BiSAR has the ability to obtain the high-resolution image of target area in the case of large squint angle and forward-looking by the path planning of missile.In addition,the bistatic geometry has greatly effects in spatial resolution.The greater the bistatic angle between transmitter and receiver is,the worse the range resolution becomes.When both the transmitter and the receiver overlap,i.e.the range resolution,is the best.The larger the angle between moving direction of transmitter and receiver is,the worse the azimuth resolution is obtained.And the azimuth resolution is the best,when the motion direction is consistent.