机载毫米波高分辨大斜视合成孔径雷达成像

Synthetic aperture radar imaging of airborne millimeter wave with high resolution and high squint

针对忽略斜距高次展开项对驻相点的影响而引入的耦合旁瓣问题,提出基于完整斜距求频谱的机载毫米波高分辨大斜视合成孔径雷达(SAR)成像方法,在不对斜距进行级数展开近似的前提下,利用驻相点法求取基于完整斜距的精确二维频谱表达式,并将求取的精确二维频谱展开为距离频率和方位频率的幂级数.在成像处理时,距离维以场景中心斜距作为参考校正距离频率的三次相位项,对于距离频率二次以内相位部分采用线频调变标(CS)处理,推导出相应的CS处理参数及变标表达式.在方位维处理中,推导出基于级数反演求驻相点的方位NCS处理参数及表达式.结合推导出的二维精确频谱,给出在高分辨大斜视应用下结合距离三次项校正的成像处理流程及表达式.利用推导结果进行机载毫米波高分辨大斜视SAR的仿真实验,结果表明:所提出的方法在分辨率为0.1m、斜视角为70°的情况下能较好地实现对场景中心点目标的聚焦;对于点阵目标,采用基于完整斜距的成像模型大大减少了耦合旁瓣,聚焦效果较好.

The synthetic aperture radar （SAR） imaging processing method for airborne millimeter wave high resolution high squint was proposed based on the frequency spectrum computation using complete slant range, in order to solve the coupling side-lobe problems brought by neglect of the impact of slant distance higher order items on stationary phase point. The proposed algorithm could compute accurate two-dimensional spectrum expression by using stationary phase point method based on complete slant range instead of slant range series expansion. Then unfold the accurate two-dimensional spectrum expression into the power series of range frequency and azimuth frequency. During the imaging processing, range dimensional was corrected by the range frequency third order term according to the scenes center range. The range frequency phase terms no more than two order were processed hy chirp scaling （CS）, and the CS processing parameters and scaling expressions were deduced. During the azimuth processing, the azimuth nonlinear chirp scaling （NCS） parameters and expressions were also deduced based on the series reversion for phase point. On the basis of the accurate two-dimensional spectrum, the imaging processing flowchart and expressions that combined with range third order term correction were given under high resolution and large squint application. Airborne millimeter wave high resolution high squint SAR simulation were taken using the deduced methods. Results show that the proposed method play well n image focusing for the point target in scene center at the resolution of 0. 1 m and the squint angle of 70°. range were reduced a lot,