步进频SAR的波数域成像算法研究

Stepped Frequency SAR Imaging Using Wavenumber Domain Algorithm

步进频合成孔径雷达(SAR)可以在不要求系统瞬时大带宽的情况下获得距离向高分辨率,在一些领域已得到了成功的应用,但其成像过程中由于雷达与目标之间存在相对运动使得脉冲间对应的瞬时斜距有不可忽略的差值,基于差值导致的距离像偏移、分辨率下降和信噪比损失,提出了在二维频域中补偿的方法。波数域成像算法主要操作是在二维频域,成像精度较高,计算量适中,文中将该算法应用到步进频SAR中,从雷达的几何关系和信号回波模型出发,推导了补偿斜距差的公式,以及实现残余压缩的Stolt插值过程,给出了目标精确聚焦的完整步骤,并分析了Stolt插值频率改变的过程和参数设计的影响,最后对多个点目标进行了成像仿真。

Stepped frequency SAR can obtain the high resolution without the large instantaneous bandwidth,has been successfully used in several areas. Due to relative motion between radar and target there is no negligible instantaneous slant distance difference between pulses. The difference is analyzed in detail,which leads to the decrease of the range profile like offset,resolution and SNR loss. A method of compensation in two-dimensional frequency domain is proposed. The wavenumber domain imaging algorithm mainly operates in two dimensional frequency domain with the higher imaging accuracy and a moderate amount of calculation. So the algorithm is applied to stepped frequency SAR. Starting from the geometric relation and the echo signal model,the formula for compensating the slant distance difference and the Stolt interpolation method to implement residual compression are derived. The complete steps of target’s precise focusing are given. The frequency change process of Stolt interpolation and the influence of parameter design of the process are analyzed. Finally,the imaging simulation of multiple point targets is carried out.