利用多频段地面数字电视广播信号作为外辐射源,进行了无源逆合成孔径雷达成像算法研究。通过获取非相邻通道的信号,巧妙地扩展了信号频带,使之频带宽度足够宽而能在成像中获得足够高的分辨率。在传统的雷达成像方法中需要花大力气做回波的距离对准和相位对准的运动补偿。文中提出利用时频分析的方法,避免复杂的运动补偿,只要在距离向上对准,多普勒即可认为是非时变的,这在很大程度上减少对运动补偿的依赖,使目标在做较为复杂的运动时也能得到清晰的成像结果。并且,针对噪声较大的情况下的成像,在短时傅里叶变换(STFT)的时频分析法成像的基础上,利用CLEAN算法,通过对图像的解卷积滤波,去掉噪声带来的干扰,提取出散射点的位置信息。对比一般的成像算法,仿真实验表明,文中提出的STFT+CLEAN算法的成像结果更为清晰准确。

The passive ISAR imaging algorithm using the multi-channel DVB-T signals as the opportunity illuminators is studied in this paper. The signals' band can be extended by obtaining the signals from non-adjacent channels, so that the bandwidth can be wide enough to get sufficiently high resolution. Great efforts must be done to do the distance and phase alignments when using conventional method for radar imaging. Algorithm based on time-frequency analysis is introduced in this paper to avoid the complex motion compensation. As long as the distance aligned, Doppler frequency can be considered to be constant, which reduces the dependence of the motion compensation. What's more, for the case of noisy environment, based on the time-frequency analysis, the CLEAN algorithm is used to extract the location information of scatters. Simulation results demonstrate that the proposed STFT + CLEAN algorithm can achieve more accurate results.