超高分辨率超宽带SAR成像技术研究
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摘要
近年来,合成孔径雷达技术取得了迅猛的发展。在此期间,分辨率的提高依然是重要的发展方向。
距离向实现超高分辨率需要超大带宽信号,以0.1m分辨率为例,需要1.5GHz的信号带宽,直接实现如此大的信号带宽是相当困难的,采用常规方法也是不现实的。本文采用基于频率步进线性调频信号的合成带宽技术用来实现超大带宽信号。合成带宽技术的基本思路是把一个大带宽的线性调频信号分割成几个子线性调频信号,子信号的中心频率以一定的步长增加。每次发射一个子信号,回波信号使用信号处理技术联合各个子信号得到一个全带宽的合成信号,实现高距离分辨率。本文提出了一种脉冲压缩先于合成带宽的处理方法,具有处理步骤简单,运算量小的优点。接着讨论了雷达与目标的相对运动对合成带宽的影响,并给出了这种影响可以忽略的约束条件。
方位向高分辨率要求更长的孔径积累时间,导致距离弯曲增大；加上距离向分辨率很高,这都要求成像算法更加精确。本文基于脉冲压缩先于合成带宽处理的原理,采用成像处理先于合成带宽的方法,提出了结合合成带宽的距离迁移算法和后向投影算法,使成像算法可以方便地和合成带宽技术结合起来,具有操作简便,运算量小的优点。从理论上说明了距离迁移算法与后向投影算法的一致性。针对目前缺乏可用于合成带宽的实测数据的情况,提出了一种将一般数据转换成频率步进线性调频信号数据的方法,为在没有合成带宽实测数据的情况下研究合成带宽方法提供了一种途径。
Recently, Synthetic Aperture Radar (SAR) has been developing quickly. In these years, improving the resolution is still an important tendency of development.
Ultra-high range resolution requires ultra-wideband signal. For example,0.1m range resolution requires 1.5GHz signal bandwidth, implementing this type of ultra-wideband signal directly is very difficult and normal method is unrealistic. In this paper, a synthetic bandwidth method which based on stepped-frequency chirps is used to realize the ultra-wideband signal.The basic thinking of this method is cutting the total bandwidth signal to several sub-signal, each sub-signal have a smaller bandwidth, the center frequency of each sub-signal is stepped-frequency, and then combining each sub-signal to a total bandwidth signal to attain high range resolution. A pulse compression before synthetic bandwidth processing method is proposed in this paper. This method has the advantages of simple processing steps and less computational amount. The influence of the motion between radar and target to synthetic bandwidth processing is discussed, and the constraint under which the influence can be neglected is derived.
Ultra-high azimuth resolution imaging requires long integration time, which leads to a serious range curvature, considering ultra-high range resolution additionally, there requires a high precise imaging algorithm. Based on the principle of pulse compression before synthetic bandwidth processing, we use the method of imaging before synthetic bandwidth processing, and proposed the range migration algorithm and backprojection algorithm which combined with synthetic bandwidth. This lead to the convenience of combing imaging algorithm with synthetic bandwidth and the advantages of simple processing and less computational amount. The consistency of range migration algorithm and backprojection algorithm is discussed theoretically. Considering the lack of real SAR data for synthetic bandwidth, this paper proposed an approach to transform the common SAR data to frequency-stepped chirps, this transform supplies an approach to investigate synthetic bandwidth method under the condition of lack of real synthetic bandwidth data.
距离向实现超高分辨率需要超大带宽信号,以0.1m分辨率为例,需要1.5GHz的信号带宽,直接实现如此大的信号带宽是相当困难的,采用常规方法也是不现实的。本文采用基于频率步进线性调频信号的合成带宽技术用来实现超大带宽信号。合成带宽技术的基本思路是把一个大带宽的线性调频信号分割成几个子线性调频信号,子信号的中心频率以一定的步长增加。每次发射一个子信号,回波信号使用信号处理技术联合各个子信号得到一个全带宽的合成信号,实现高距离分辨率。本文提出了一种脉冲压缩先于合成带宽的处理方法,具有处理步骤简单,运算量小的优点。接着讨论了雷达与目标的相对运动对合成带宽的影响,并给出了这种影响可以忽略的约束条件。
方位向高分辨率要求更长的孔径积累时间,导致距离弯曲增大；加上距离向分辨率很高,这都要求成像算法更加精确。本文基于脉冲压缩先于合成带宽处理的原理,采用成像处理先于合成带宽的方法,提出了结合合成带宽的距离迁移算法和后向投影算法,使成像算法可以方便地和合成带宽技术结合起来,具有操作简便,运算量小的优点。从理论上说明了距离迁移算法与后向投影算法的一致性。针对目前缺乏可用于合成带宽的实测数据的情况,提出了一种将一般数据转换成频率步进线性调频信号数据的方法,为在没有合成带宽实测数据的情况下研究合成带宽方法提供了一种途径。
Recently, Synthetic Aperture Radar (SAR) has been developing quickly. In these years, improving the resolution is still an important tendency of development.
Ultra-high range resolution requires ultra-wideband signal. For example,0.1m range resolution requires 1.5GHz signal bandwidth, implementing this type of ultra-wideband signal directly is very difficult and normal method is unrealistic. In this paper, a synthetic bandwidth method which based on stepped-frequency chirps is used to realize the ultra-wideband signal.The basic thinking of this method is cutting the total bandwidth signal to several sub-signal, each sub-signal have a smaller bandwidth, the center frequency of each sub-signal is stepped-frequency, and then combining each sub-signal to a total bandwidth signal to attain high range resolution. A pulse compression before synthetic bandwidth processing method is proposed in this paper. This method has the advantages of simple processing steps and less computational amount. The influence of the motion between radar and target to synthetic bandwidth processing is discussed, and the constraint under which the influence can be neglected is derived.
Ultra-high azimuth resolution imaging requires long integration time, which leads to a serious range curvature, considering ultra-high range resolution additionally, there requires a high precise imaging algorithm. Based on the principle of pulse compression before synthetic bandwidth processing, we use the method of imaging before synthetic bandwidth processing, and proposed the range migration algorithm and backprojection algorithm which combined with synthetic bandwidth. This lead to the convenience of combing imaging algorithm with synthetic bandwidth and the advantages of simple processing and less computational amount. The consistency of range migration algorithm and backprojection algorithm is discussed theoretically. Considering the lack of real SAR data for synthetic bandwidth, this paper proposed an approach to transform the common SAR data to frequency-stepped chirps, this transform supplies an approach to investigate synthetic bandwidth method under the condition of lack of real synthetic bandwidth data.
引文
[1]李海英、杨汝良.超宽带雷达的发展、现状及应用.遥感技术及应用,Vol.16,No.3, sep.2001.
[2]保铮、邢孟道、王彤.雷达成像技术.北京：电子工业出版社,2005
[3]刘永坦.雷达成像技术.哈尔滨：哈尔滨工业大学,2001
[4]张澄波.综合孔径雷达.北京：科学出版社,1989
[5]A.Reigber,E.Alivizatos,A.Potsis and A.Moreira.Extend Wavenumber-domain Synthetic Aperture Radar Focusing With Integrated Motion Compensation.IEE Proc.-Radar Sonar Navig.,2006,301-310
[6]C.Cafforio,C.Prati,F.Rocca.SAR Data Focusing Using Seismic Migration Techniques. IEEE Transactions on Aerospace and Electronic Systems,1991,194-207
[7]Richard Bamler.A Comparison of Range-Doppler And Wavenumber Domain SAR Focusing Algorithms.IEEE Transactions on Geoscience and Remote Sensing,1992,706-713
[8]金添.超宽带SAR浅埋目标成像与检测的理论和技术研究.长沙：国防科学技术大学博士学位论文.2007
[9]白霞、毛士艺、袁运能.时域合成带宽方法：一种0.1米分辨率SAR技术.电子学报,2006
[10]H.Wilden,B.Poppelreuter,O.Saalmann, A.R.Brenner, J.H.G.Ender. Design And Realization Of The PAMIR Antenna frontend. Proc. EUSAR 2004,2004
[11]J.H.G.Ender,A.R.Brenner. PAMIR-A Wideband Phased Array SAR/MTI System. IEE Proc-Radar,Sonar,Navigation,2003
[12]D.Cerutti-Maori,U.Skupin. First Experimental Scan MTI results achieved With the Multi-Channel SAR System PAMIR. Proc. EUSAR 2004,2004
[13]A.R.Brenner, J.H.G.Ender. Very Wideband Radar With The Airborne SAR Sensor PAMIR. Proc. IGARSS,2003
[14]A.R.Brenner, J.H.G.Ender. First Experimental Results Achieved With The New Very Wideband SAR System PAMIR. Proc. EUSAR 2002,2002
[15]J.H.G.Ender,A.R.Brenner. PAMIR-A Wideband Phased Array SAR/MTI System. Proc. EUSAR 2002,2002
[16]刘光平,超宽带合成孔径雷达高效成像算法,长沙：国防科学技术大学,2003
[17]向敬成、张明友.雷达系统.北京：电子工业出版社,2001
[18]丁鹭飞、耿富录,雷达原理(第三版),西安电子科技大学出版社,2002
[19]A.Milman. SAR Imaging by ω-k Migration. Int. J. Remote Sens.,1993
[20]John W.McCorkle. Focusing of Synthetic Aperture Ultra Wideband Data. IEEE Trans. On AES.,1991
[21]A.R.Brenner. Distributed SAR Processing In the Time Domain. Proc. EUSAR 2002,2002
[22]M.D.Desai,W.K.Jenkins. Convolution Back-Projection Image Reconstruction for Spotlight Mode Synthetic Aperture Radar. IEEE Trans. on Image Processing,1992
[23]M.Skolnik,G.Linde,K.Meads. Senrad:An Advanced Wideband Air Surveillance Radar. IEEE on AES,2001
[24]G.Fornaro,G.Franceschetti,S.Perna. Motion Compensation Errors:Effects on the Accuracy of Airborne SAR Images. IEEE Trans. On AES,2005
[25]C.Prati,F.Rocca,A.Guarnieri. Seismic Migration for SAR Focusing:Interferometrical Applications. IEEE Trans. On GRS,1990
[26]M.Soumekh. Synthetic Aperture Radar Signal Processing. New York:John Wiley & Sons,inc.,1999
[27]A.Moreira,J.Mittermayer,R.Scheiber. Extended Chirp Scaling Algorithm for Air-and Spaceborne SAR Data Processing in Stripmap and ScanSAR Imaging Modes. IEEE Trans. On GRS,1996
[28]张去华、李海宾、伍捷,步进频率线性调频脉冲信号的子孔径处理方法,系统工程与电子技术,Jan 2006
[29]姚萍、郑天垚、王侦松,线性调频步进式合成孔径雷达系统的信号处理,系统工程与电子技术,Feb 2006
[30]李海英、杨汝良,频率步进信号的合成孔径雷达处理,电子学报,Mar 2003
[31]Aining Li,Otmar Loffeld.Two Dimensional SAR Processing In the Frequency Domain.1991 IEEE
[32]T.E.Scheuer,F.H.Wong.Comparison of SAR Processing Based on a Wave Equation Formulation.1991 IEEE
[33]L.M.H.Ulander,H.Hellsten,G.Stenstrom.Synthetic-Aperture Radar Processing Using Fast Factorized Back-Projection. IEEE Transactions on Aerospace and Electronic Systems,July 2003
[34]Ali F.Yegulalp.Fast Backprojection Algorithm for Synthetic Aperture,Radar.IEEE 1999
[35]邹鲲、梁甸农,基于波数域聚焦算法的低频UWB SAR成像,现代雷达,Feb2005
[36]陈仁元、邓海涛、江凯、雍延梅、张长耀,机载高分辨SAR系统成像技术,遥感技术与应用,Feb 2005
[37]姜忠良、周智敏、常文革,距离迁移成像算法在超宽带SAR成像中的应用, 雷达科学与技术,Feb 2004
[2]保铮、邢孟道、王彤.雷达成像技术.北京：电子工业出版社,2005
[3]刘永坦.雷达成像技术.哈尔滨：哈尔滨工业大学,2001
[4]张澄波.综合孔径雷达.北京：科学出版社,1989
[5]A.Reigber,E.Alivizatos,A.Potsis and A.Moreira.Extend Wavenumber-domain Synthetic Aperture Radar Focusing With Integrated Motion Compensation.IEE Proc.-Radar Sonar Navig.,2006,301-310
[6]C.Cafforio,C.Prati,F.Rocca.SAR Data Focusing Using Seismic Migration Techniques. IEEE Transactions on Aerospace and Electronic Systems,1991,194-207
[7]Richard Bamler.A Comparison of Range-Doppler And Wavenumber Domain SAR Focusing Algorithms.IEEE Transactions on Geoscience and Remote Sensing,1992,706-713
[8]金添.超宽带SAR浅埋目标成像与检测的理论和技术研究.长沙：国防科学技术大学博士学位论文.2007
[9]白霞、毛士艺、袁运能.时域合成带宽方法：一种0.1米分辨率SAR技术.电子学报,2006
[10]H.Wilden,B.Poppelreuter,O.Saalmann, A.R.Brenner, J.H.G.Ender. Design And Realization Of The PAMIR Antenna frontend. Proc. EUSAR 2004,2004
[11]J.H.G.Ender,A.R.Brenner. PAMIR-A Wideband Phased Array SAR/MTI System. IEE Proc-Radar,Sonar,Navigation,2003
[12]D.Cerutti-Maori,U.Skupin. First Experimental Scan MTI results achieved With the Multi-Channel SAR System PAMIR. Proc. EUSAR 2004,2004
[13]A.R.Brenner, J.H.G.Ender. Very Wideband Radar With The Airborne SAR Sensor PAMIR. Proc. IGARSS,2003
[14]A.R.Brenner, J.H.G.Ender. First Experimental Results Achieved With The New Very Wideband SAR System PAMIR. Proc. EUSAR 2002,2002
[15]J.H.G.Ender,A.R.Brenner. PAMIR-A Wideband Phased Array SAR/MTI System. Proc. EUSAR 2002,2002
[16]刘光平,超宽带合成孔径雷达高效成像算法,长沙：国防科学技术大学,2003
[17]向敬成、张明友.雷达系统.北京：电子工业出版社,2001
[18]丁鹭飞、耿富录,雷达原理(第三版),西安电子科技大学出版社,2002
[19]A.Milman. SAR Imaging by ω-k Migration. Int. J. Remote Sens.,1993
[20]John W.McCorkle. Focusing of Synthetic Aperture Ultra Wideband Data. IEEE Trans. On AES.,1991
[21]A.R.Brenner. Distributed SAR Processing In the Time Domain. Proc. EUSAR 2002,2002
[22]M.D.Desai,W.K.Jenkins. Convolution Back-Projection Image Reconstruction for Spotlight Mode Synthetic Aperture Radar. IEEE Trans. on Image Processing,1992
[23]M.Skolnik,G.Linde,K.Meads. Senrad:An Advanced Wideband Air Surveillance Radar. IEEE on AES,2001
[24]G.Fornaro,G.Franceschetti,S.Perna. Motion Compensation Errors:Effects on the Accuracy of Airborne SAR Images. IEEE Trans. On AES,2005
[25]C.Prati,F.Rocca,A.Guarnieri. Seismic Migration for SAR Focusing:Interferometrical Applications. IEEE Trans. On GRS,1990
[26]M.Soumekh. Synthetic Aperture Radar Signal Processing. New York:John Wiley & Sons,inc.,1999
[27]A.Moreira,J.Mittermayer,R.Scheiber. Extended Chirp Scaling Algorithm for Air-and Spaceborne SAR Data Processing in Stripmap and ScanSAR Imaging Modes. IEEE Trans. On GRS,1996
[28]张去华、李海宾、伍捷,步进频率线性调频脉冲信号的子孔径处理方法,系统工程与电子技术,Jan 2006
[29]姚萍、郑天垚、王侦松,线性调频步进式合成孔径雷达系统的信号处理,系统工程与电子技术,Feb 2006
[30]李海英、杨汝良,频率步进信号的合成孔径雷达处理,电子学报,Mar 2003
[31]Aining Li,Otmar Loffeld.Two Dimensional SAR Processing In the Frequency Domain.1991 IEEE
[32]T.E.Scheuer,F.H.Wong.Comparison of SAR Processing Based on a Wave Equation Formulation.1991 IEEE
[33]L.M.H.Ulander,H.Hellsten,G.Stenstrom.Synthetic-Aperture Radar Processing Using Fast Factorized Back-Projection. IEEE Transactions on Aerospace and Electronic Systems,July 2003
[34]Ali F.Yegulalp.Fast Backprojection Algorithm for Synthetic Aperture,Radar.IEEE 1999
[35]邹鲲、梁甸农,基于波数域聚焦算法的低频UWB SAR成像,现代雷达,Feb2005
[36]陈仁元、邓海涛、江凯、雍延梅、张长耀,机载高分辨SAR系统成像技术,遥感技术与应用,Feb 2005
[37]姜忠良、周智敏、常文革,距离迁移成像算法在超宽带SAR成像中的应用, 雷达科学与技术,Feb 2004