频率步进合成孔径雷达(Synthetic Aperture Radar,SAR)的系统传递函数中存在幅度和相位误差(Magnitude Error and Phase Error,MEPE),通过宽带合成操作在距离宽带信号中引入了周期性MEPE,从而导致宽带合成后的高分辨率距离像(HRRP)中出现周期性栅瓣.经过后续SAR成像处理,这些周期性栅瓣在图像中表现为虚假目标,严重影响SAR图像目标的检测与识别.为此,基于SAR图像的栅瓣抑制(Grating Lobe Suppression,GLS)算法被提出,其基于点状目标假设,利用SAR图像中的强点目标实现图像栅瓣的有效抑制.然而,对于非点状目标场景,已有基于SAR图像的GLS算法的性能显著下降,而且会引起图像散焦.因此,文中提出了一种基于目标信息差异的GLS算法,取名为目标信息差异法.该算法不基于点状目标假设,通过估计宽带合成后的理想HRRP与实际HRRP之间的信息差异,稳健地估计出合成宽带信号中的周期性MEPE.通过补偿该周期性MEPE,该算法可以将频率步进SAR距离向栅瓣抑制到图像的背景水平.通过对不同GLS算法进行性能对比发现,所提GLS算法受图像信杂比影响小,且同时适用于非点状目标和点状目标场景,相比已有GLS算法具有明显的优势.实测数据处理结果证明了所提方法的有效性和相对已有GLS算法的优越性.
A Robust Method for Range Grating Lobe Suppression in Stepped Frequency SAR
The magnitude error and phase error(MEPE)in the system transfer function of the stepped-frequency synthetic aper-ture radar(SAR)introduces periodic MEPE in the synthesized wideband signal,resulting in periodic grating lobes in the high-re-solution range profile(HRRP).After subsequent SAR imaging processing,these periodic grating lobes appear as false targets in the SAR image,seriously affecting SAR image target detection and recognition.Therefore,the GLS algorithm based on SAR ima-ges has been proposed,which is based on the assumption of point targets and effectively suppresses image grating lobes by utili-zing strong point targets in SAR images.However,for non-point target scenes,existing GLS algorithms based on SAR images can cause image defocusing while suppressing image grating lobes.Therefore,this paper proposes a GLS algorithm based on target in-formation differences,named the target information difference method,which is not based on the assumption of point-shaped tar-gets.By estimating the information difference between the ideal HRRP and the actual HRRP of the target after wideband synthe-sis,it can robustly estimate the periodic MEPE in the synthesized wideband signal.By compensating for this periodic MEPE,the algorithm can suppress the range grating lobes to the SAR image background level.By comparing the performance of different GLS algorithms,it is found that the proposed GLS algorithmis less affected by the image signal-to-noise ratio and is suitable for both non-point target and point target scenes,thus having obvious advantages comparing to existing GLS algorithms.Experimen-tal data processing results demonstrate the effectiveness and superiority of the proposed method compared to existing GLS algo-rithms.
Grating lobe suppressionStepped frequency synthetic aperture radarBackground levelBroadband signalImage de-focus
万方数据
维普
