基于距离子带的机载SAR高精度多级空变运动补偿
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摘要
运动补偿(MOCO)是机载合成孔径雷达(SAR)获取高质量图像的关键,超高分辨率成像中,如何精确、高效地校正空变运动误差仍是很大的挑战。本文提出了一种改进的多级空变运动补偿方案,兼顾处理的精度和效率。首先,采用一步运动补偿法有效去除运动误差的距离空变分量,避免引起额外的距离徙动校正(RCMC)误差。同时,修正视线方向误差的传统计算方式,保证相位精度的前提下结合距离子带实现无插值的近似距离包络补偿。然后,利用距离子带降低残余方位空变误差的距离空变性和对方位时频关系的影响,显著改善宽波束情况下的聚焦效果,降低孔径依赖补偿算法的运算量。最终分辨率达到0.1m,具有实际工程应用价值。点目标仿真和实测数据处理验证了所做的研究。
MOtion COmpensation(MOCO)is the key to acquisition of high quality images by the airborne Synthetic Aperture Radar(SAR).In ultra-high resolution imaging,it is still a great challenge to correct space-variant motion errors accurately and efficiently.In this paper,an improved approach for multi-level space-variant MOCO with multi-level processing is proposed,which gives consideration to both precision and efficiency.First,the one-step MOCO algorithm is used to correct the range-variant component of the motion error effectively,avoiding inducing additional Range Cell Migration Correction(RCMC)error.Meanwhile,on the premise that the accuracy of phase correction should be guaranteed,the conventional calculation formula for line-of-sight range displacement is revised,and an approximate range envelope compensation without complex interpolation can be implemented with the subswath.Then,the subswath is used to reduce the range variance of the residual azimuth-variant error,as well as the influence of the error on the azimuth-to-frequency mapping.Consequently,the focusing effect in the case of wide beam is improved observably,and the computational burden of the aperture-dependent compensation algorithm is also reduced.The proposed approach can attain 0.1 mresolution,being useful in engineering practice.Simulations of point targets and processing of test data have validated the present research.
MOtion COmpensation(MOCO)is the key to acquisition of high quality images by the airborne Synthetic Aperture Radar(SAR).In ultra-high resolution imaging,it is still a great challenge to correct space-variant motion errors accurately and efficiently.In this paper,an improved approach for multi-level space-variant MOCO with multi-level processing is proposed,which gives consideration to both precision and efficiency.First,the one-step MOCO algorithm is used to correct the range-variant component of the motion error effectively,avoiding inducing additional Range Cell Migration Correction(RCMC)error.Meanwhile,on the premise that the accuracy of phase correction should be guaranteed,the conventional calculation formula for line-of-sight range displacement is revised,and an approximate range envelope compensation without complex interpolation can be implemented with the subswath.Then,the subswath is used to reduce the range variance of the residual azimuth-variant error,as well as the influence of the error on the azimuth-to-frequency mapping.Consequently,the focusing effect in the case of wide beam is improved observably,and the computational burden of the aperture-dependent compensation algorithm is also reduced.The proposed approach can attain 0.1 mresolution,being useful in engineering practice.Simulations of point targets and processing of test data have validated the present research.
引文
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[14]YANG M D,ZHU D Y,SONG W.Comparison of twostep and one-step motion compensation algorithms for airborne synthetic aperture radar[J].Electronics Letters,2015,51(14):1108-1110.
[15]TANG S Y,ZHANG L R,GUO P,et al.Processing of monostatic SAR data with general configurations[J].IEEE Transactions on Geoscience and Remote Sensing,2015,53(12):6529-6546.
[16]FORNARO G,FRANCESCHETTI G,PERNA S.Motion compensation errors:Effects on the accuracy of airborne SAR images[J].IEEE Transactions on Aerospace and Electronic Systems,2005,41(4):1338-1352.
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[18]PRATS-IRAOLA P,SCHEIBER R,RODRIGUEZ-CAS-SOLA M,et al.On the processing of very high resolution spaceborne SAR data[J].IEEE Transactions on Geoscience and Remote Sensing,2014,52(10):6003-6016.
[19]FORNARO G,FRANCESCHETTI G,PERNA S.On center-beam approximation in SAR motion compensation[J].IEEE Geoscience and Remote Sensing Letters,2006,3(2):276-280.
[20]曾乐天,邢孟道,陈士超.基于窄波束和平地假设的运动补偿方向研究[J].电子与信息学报,2014,36(10):2464-2468.ZENG L T,XING M D,CHEN S C.The research on the direction of motion compensation according to the narrow beam and flat earth hypothesis[J].Journal of Electronics and Information Technology,2014,36(10):2464-2468(in Chinese).
[21]毛新华,朱岱寅,朱兆达.复杂航迹和起伏地形条件下机载聚束SAR空变运动补偿[J].航空学报,2012,33(4):744-754.MAO X H,ZHU D Y,ZHU Z D.Space-variant motion compensation for airborne spotlight SAR under complicated flight path and rugged terrain[J].Acta Aeronautica et Astronautica Sinica,2012,33(4):744-754(in Chinese).
[22]CUMMING I G,WONG F H.Digital processing of synthetic aperture radar data:Algorithms and implementation[M].Norwood,MA:Artech House,2005:473-475.
[2]CANTALLOUBE H M J,NAHUM C E.Airborne SAR-efficient signal processing for very high resolution[J].Proceedings of the IEEE,2013,101(3):784-797.
[3]FORNARO G.Trajectory deviations in airborne SAR:Analysis and compensation[J].IEEE Transactions on Aerospace and Electronic Systems,1999,35(3):997-1009.
[4]MOREIRA A,MITTERMAYER J,SCHEIBER R.Extended chirp scaling algorithm for air-and spaceborne SARdata processing in stripmap and ScanSAR imaging modes[J].IEEE Transactions on Geoscience and Remote Sensing,1996,34(5):1123-1136.
[5]REIGBER A,ALIVIZATOS E,POTSIS A,et al.Extended wavenumber-domain synthetic aperture radar focusing with integrated motion compensation[J].IEE proceedings-Radar,Sonar and Navigation,2006,153(3):301-310.
[6]BUCKREUSS S.Motion compensation for airborne SARbased on inertial data,RDM and GPS[C]∥Geoscience and Remote Sensing Symposium.Piscataway,NJ:IEEEPress,1994:1971-1973.
[7]MENG D D,HU D H,DING C B.Precise focusing of airborne SAR data with wide apertures large trajectory deviations:A chirp modulated back-projection approach[J].IEEE Transactions on Geoscience and Remote Sensing,2015,53(5):2510-2519.
[8]MACEDO K A C D E,SCHEIBER R.Precise topography-and aperture-dependent motion compensation for airborne SAR[J].IEEE Geoscience and Remote Sensing Letters,2004,2(2):172-176.
[9]PRATS P,MACEDO K A C D E,REIGBER A,et al.Comparison of topography-and aperture-dependent motion compensation algorithms for airborne SAR[J].IEEE Geoscience and Remote Sensing Letters,2007,4(3):349-353.
[10]DING Z G,LIU L S,ZENG T,et al.Improved motion compensation approach for squint airborne SAR[J].IEEETransactions on Geoscience and Remote Sensing,2013,51(8):4378-4387.
[11]杨鸣冬,朱岱寅.结合视线方向运动补偿的滑动聚束SAR子孔径成像算法[J].航空学报,2016,37(3):984-996.YANG M D,ZHU D Y.An imaging approach for sliding spotlight SAR using subaperture with line-of-sight motion compensation[J].Acta Aeronautica et Astronautica Sinica,2016,37(3):984-996(in Chinese).
[12]宋伟,朱岱寅,叶少华.基于数值计算的机载SAR空变运动补偿算法[J].航空学报,2015,36(2):625-632.SONG W,ZHU D Y,YE S H.Airborne SAR space-variant motion compensation algorithm based on numerical calculation[J].Acta Aeronautica et Astronautica Sinica,2015,36(2):625-632(in Chinese).
[13]ZENG L T,LIANG Y,XING M D,et al.A novel motion compensation approach for airborne spotlight SAR of high-resolution and high-squint mode[J].IEEE Geoscience and Remote Sensing Letters,2016,13(3):429-433.
[14]YANG M D,ZHU D Y,SONG W.Comparison of twostep and one-step motion compensation algorithms for airborne synthetic aperture radar[J].Electronics Letters,2015,51(14):1108-1110.
[15]TANG S Y,ZHANG L R,GUO P,et al.Processing of monostatic SAR data with general configurations[J].IEEE Transactions on Geoscience and Remote Sensing,2015,53(12):6529-6546.
[16]FORNARO G,FRANCESCHETTI G,PERNA S.Motion compensation errors:Effects on the accuracy of airborne SAR images[J].IEEE Transactions on Aerospace and Electronic Systems,2005,41(4):1338-1352.
[17]PERNA S,ZAMPARELLI V,PAUCIULLO A,et al.Azimuth-to-frequency mapping in airborne SAR data corrupted by uncompensated motion errors[J].IEEE Geoscience and Remote Sensing Letters,2013,10(10):1493-1497.
[18]PRATS-IRAOLA P,SCHEIBER R,RODRIGUEZ-CAS-SOLA M,et al.On the processing of very high resolution spaceborne SAR data[J].IEEE Transactions on Geoscience and Remote Sensing,2014,52(10):6003-6016.
[19]FORNARO G,FRANCESCHETTI G,PERNA S.On center-beam approximation in SAR motion compensation[J].IEEE Geoscience and Remote Sensing Letters,2006,3(2):276-280.
[20]曾乐天,邢孟道,陈士超.基于窄波束和平地假设的运动补偿方向研究[J].电子与信息学报,2014,36(10):2464-2468.ZENG L T,XING M D,CHEN S C.The research on the direction of motion compensation according to the narrow beam and flat earth hypothesis[J].Journal of Electronics and Information Technology,2014,36(10):2464-2468(in Chinese).
[21]毛新华,朱岱寅,朱兆达.复杂航迹和起伏地形条件下机载聚束SAR空变运动补偿[J].航空学报,2012,33(4):744-754.MAO X H,ZHU D Y,ZHU Z D.Space-variant motion compensation for airborne spotlight SAR under complicated flight path and rugged terrain[J].Acta Aeronautica et Astronautica Sinica,2012,33(4):744-754(in Chinese).
[22]CUMMING I G,WONG F H.Digital processing of synthetic aperture radar data:Algorithms and implementation[M].Norwood,MA:Artech House,2005:473-475.