机载双站SAR成像算法改进及参数估计方法研究
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摘要
机载双站合成孔径雷达(Airborne Bistatic Synthetic Aperture Radar—AirbornBi-SAR)是一种以飞机为平台载体,收、发平台分置的SAR系统,它具有作用距离远、抗干扰性能好、隐蔽性强、能获取丰富目标信息等特点,是现在国内外雷达系统研究的热点。
由于机载双站SAR收、发分置的特点,在系统设计和信号处理的实现中会面临新的技术难题。其空间几何模型更多样化,回波信号更加复杂,因此,存在着诸如成像方法,多普勒参数估计,以及收、发同步等技术问题。本论文针对相关技术问题主要进行了以下工作:
1.对常见的几种机载双站SAR飞行模式进行了几何建模,并对其回波模型、多普勒特性进行了分析;研究分析了收、发双站基线偏角、俯仰角、各自的速度以及收、发站波束中心距离与距离向、方位向分辨率的关系。
2.讨论了双站SAR距离-多普勒(Rang-Doppler—RD)成像算法;分析研究了在双站斜视和双站SAR特有的基线不垂直情况下的两种改进RD算法:二次距离压缩算法和斜视成像模式算法,并通过仿真分析检验了RD算法及其改进算法各自的适用性、局限性及各自的优缺点。
3.对实际飞行试验获得的实测数据分别采用双站RD算法及其改进算法进行了成像处理,并得到了较好的实测数据图像,验证了这三种算法在平飞模式下的有效性。在实测数据预处理中,分析了PRF线性同步误差的产生原因及影响,采用了基于Radon变换的PRF线性同步误差补偿方法,并通过对实测数据的处理验证了其有效性。
4.从时域和频域两方面研究了多普勒质心估计方法,并对这两种情况下算法的应用情况进行了仿真和对比,分析了各自的适用条件。
5.研究了几种自聚焦算法,利用这几种算法对机载双站SAR飞行试验实测数据进行了多普勒调频斜率估计和成像,验证了其在平飞模式下的适用性,并总结比较了这几种算法的优点和局限性。
Airborne Bistatic Synthetic Aperture Radar (Bi-SAR) is a kind of SAR systerm whose transmitter and receiver are located on different airplanes as their platforms. It has the advantages of long detecting distance, capability of countering vulnerability, high security, ability of obtaining rich information etc., so the theoretical and experimental researches of Bistatic SAR are actively carried out in many countries and institutions.
With the characteristi of separated transmitter and receiver, there will be many technic problems in system design and signal processing. The geometrical models will be more various and echo signals will be more complex. Then the technic problems such as imaging algorithms, Doppler parameters estimation, and synchronization and so on need to be solved. The main work of this thesis is shown as follows:
1. Research on different geometrical models of the airborne Bi-SAR. The characteristics of echo model and Doppler characteristics are analysed. The relationship between the resolution and flight situations is discussed.
2. The Bi-SAR Range-Doppler (RD) algorithm is researched, and the improved RD algorithms: Second Range Compression (SRC) algorithm amd Squint Imaging Mdoel (SIM) algorithm are used in the situations of squint model or the base line angle which is not zero. The applicabilitys of RD algorithm and its improved algorithms are verified through simulation experiments.
3. Bi-SAR RD algorithm and its improved algorithms are used to process the experimental data of Bi-SAR flight experiment. The Bi-SAR images used these algorithms are generated sucessfully. The method based on Radon transform is shown to compensate the PRF linear synchronization error of the experimental data during the ex-processing.
4. The Bi-SAR Doppler center estimation algorithms are studied in both time domain and frequency domain. The results of simulation are shown to analyse the advantage and limitation of each algorithm.
5. The Bi-SAR autofocus algorithms are studied and used to process the experimental data of airborn bistatic SAR flight experiment. Their applicabilitys are verified under the condition of parallel flight model. The advantages and limitations of these algorithms are discussed finally.
由于机载双站SAR收、发分置的特点,在系统设计和信号处理的实现中会面临新的技术难题。其空间几何模型更多样化,回波信号更加复杂,因此,存在着诸如成像方法,多普勒参数估计,以及收、发同步等技术问题。本论文针对相关技术问题主要进行了以下工作:
1.对常见的几种机载双站SAR飞行模式进行了几何建模,并对其回波模型、多普勒特性进行了分析;研究分析了收、发双站基线偏角、俯仰角、各自的速度以及收、发站波束中心距离与距离向、方位向分辨率的关系。
2.讨论了双站SAR距离-多普勒(Rang-Doppler—RD)成像算法;分析研究了在双站斜视和双站SAR特有的基线不垂直情况下的两种改进RD算法:二次距离压缩算法和斜视成像模式算法,并通过仿真分析检验了RD算法及其改进算法各自的适用性、局限性及各自的优缺点。
3.对实际飞行试验获得的实测数据分别采用双站RD算法及其改进算法进行了成像处理,并得到了较好的实测数据图像,验证了这三种算法在平飞模式下的有效性。在实测数据预处理中,分析了PRF线性同步误差的产生原因及影响,采用了基于Radon变换的PRF线性同步误差补偿方法,并通过对实测数据的处理验证了其有效性。
4.从时域和频域两方面研究了多普勒质心估计方法,并对这两种情况下算法的应用情况进行了仿真和对比,分析了各自的适用条件。
5.研究了几种自聚焦算法,利用这几种算法对机载双站SAR飞行试验实测数据进行了多普勒调频斜率估计和成像,验证了其在平飞模式下的适用性,并总结比较了这几种算法的优点和局限性。
Airborne Bistatic Synthetic Aperture Radar (Bi-SAR) is a kind of SAR systerm whose transmitter and receiver are located on different airplanes as their platforms. It has the advantages of long detecting distance, capability of countering vulnerability, high security, ability of obtaining rich information etc., so the theoretical and experimental researches of Bistatic SAR are actively carried out in many countries and institutions.
With the characteristi of separated transmitter and receiver, there will be many technic problems in system design and signal processing. The geometrical models will be more various and echo signals will be more complex. Then the technic problems such as imaging algorithms, Doppler parameters estimation, and synchronization and so on need to be solved. The main work of this thesis is shown as follows:
1. Research on different geometrical models of the airborne Bi-SAR. The characteristics of echo model and Doppler characteristics are analysed. The relationship between the resolution and flight situations is discussed.
2. The Bi-SAR Range-Doppler (RD) algorithm is researched, and the improved RD algorithms: Second Range Compression (SRC) algorithm amd Squint Imaging Mdoel (SIM) algorithm are used in the situations of squint model or the base line angle which is not zero. The applicabilitys of RD algorithm and its improved algorithms are verified through simulation experiments.
3. Bi-SAR RD algorithm and its improved algorithms are used to process the experimental data of Bi-SAR flight experiment. The Bi-SAR images used these algorithms are generated sucessfully. The method based on Radon transform is shown to compensate the PRF linear synchronization error of the experimental data during the ex-processing.
4. The Bi-SAR Doppler center estimation algorithms are studied in both time domain and frequency domain. The results of simulation are shown to analyse the advantage and limitation of each algorithm.
5. The Bi-SAR autofocus algorithms are studied and used to process the experimental data of airborn bistatic SAR flight experiment. Their applicabilitys are verified under the condition of parallel flight model. The advantages and limitations of these algorithms are discussed finally.
引文
[1]汤子跃,张守融.双站合成孔径雷达系统原理.北京,科学出版社,2003.
[2]张直中.机载和星载合成孔径雷达导论.北京,电子工业出版社,2004.
[3]皮亦鸣,杨建宇,付毓生,杨晓波.合成孔径雷达成像原理.成都,电子科技大学出版社,2007.
[4]Ian G.Cumming,Frank H.Wong著,洪文,胡东辉等译.合成孔径雷达成像--算法与实现.北京,电子工业出版社,2007.
[5]保铮,邢孟道,王彤.雷达成像技术.北京,电子工业出版社,2005.
[6]张直中.双基地合成孔径雷达.现代雷达.2005.1.Vol.7 No.1:1-6.
[7]Horne,A.M.Yates,G.Bistatic Synthetic Aperture Radar.Proceedings of Radar 2002Conference,Edinburgh,Scotland Oct.2002.IEE publication No.490:6-10.
[8]J.H.G.Ender.A step To Bistatic SAR Processing.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May 25-27,2004:359-364.
[9]Ender,J.H.G.Signal Theoretical Aspects of Bistatic SAR.IEEE International Geoscience and Remote Sensing Symposium,Tolouse,July 2003:1438-1441.
[10]Otmar Loffeld,Holger Nies.Bistatic SAR Some Reflections on Rocca's Smile.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May 25-27,2004:379-383.
[11]I Walterscheid,A.B.R.Brenner,J.H.G.Ender.Geometry and System Aspects for a Bistatic Airborne SAR-Experiment.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May25-27,2004:567-570.
[12]Pascale Dubois-Fernandez,Hubert Cantalloube.Analysis of Bistatic Scattering behavior of natural surfaces.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May 25-27,2004.
[13]G.Yates,A.M.Horne,A.P.Blake,R.Middleton,D.B.Andre.Bistatic SAR image formation.5th European Conference on Synthetic Aperture Radar,2004:208-213.
[14]D.D'Aria,A.Monti Guarnieri,F.Rocca.FocusingBistatic Synthetic Aperture Radar Using Dip Move Out.IEEE Trans.On Geoscience and Remote Sensing,2004,42(7):1362-1376.
[15]H.Cantalloube,et al.Challenges in SAR processing for airborne bistatic acquisitions.5th European Conference on Synthetic Aperture radar,2004:577-580.
[16]Joachim H.G.Ender,I.Walterscheid,Andreas R.Brenner.New aspects of bistatic SAR:processing and experiments.Anchorage,USA,IGARSS 2004,Vol.3:1758-1762.
[17]Moccia A.,Rufino G.,D'Errico M.,et al.BISSAT:a bistatic SAR for Earth observation.IGARSS '02,2002,Vol.5:2628 -2630.
[18]况凌,沈晓峰,杨万麟.机载双基地SAR成像算法比较.电子学报,2006,Vol.34No.12:3211-3214.
[19]Huang Yan,Li Chunsheng,Li Jingwen.An airborne squint SAR processing algorithm.CIE International Conference of Radar 1996,8-10 Oct.1996:334 - 337.
[20]Yulong Shao,Zhaoda Zhu.Squint mode airborne SAR processing using RD algorithm.IEEE 1997 National Aerospace and Electronics Conference,14-17 July 1997,Vol.2:1025 - 1029.
[21]Chang C.Y.,Jin M.,Curlander J.C.Squint Mode SAR Processing Algorithms.IGARSS'89,10-14 Jul.1989,Vol.3:1702 - 1706.
[22]Xian Li,Xiong Jintao,Huang Yulin,Yang Jianyu.Research on Airborne Bistatic SAR Squint Imaging Mode Algorithm and Experiment Data Processing.APSAR2007.5-9 Nov.,2007,Huangshan:618-621.
[23]刘锐.机载双站SAR同步误差分析及仿真:[硕士学位论文].电子科技大学,2006.
[24]赵志钦,刘醒凡,顾德仁.SAR多卜勒参数的时域估计.信号处理,1995,Vol.11No.1:26-30.
[25]刘国庆,黄顺吉.星载SAR多普勒质心估计的改进方法.信号处理,1994,Vol.10.No.3:156-160.
[26]Nies H.,Loffeld O.,Natroshvili K,et al.Parameter estimation for bistatic constellations.IGARSS'05,25-29 Jul.2005,Vol.2:1038-1042.
[27]Samczynski Piotr,Kulpa Krzysztof.Concept of the Coherent Autofocus Map-Drift Technique.IRS 2006,24-26 May 2006:1-4.
[28]Prodi F.,Vinelli F.,Dente,F.An autofocusing technique of SAR data based on superresolution.IGARS S'93.18-21 Aug.1993,Vol.4:1586-1588.
[29]陈琦,李景文.相位梯度自聚焦算法的性能分析及改进.北京航空航天大学学报,2004,Vol.30.No.2:131-134.
[30]D.E.Whal,D.C.Ghiglia,C.V.Jakowatz.A new approach to Stripmap SAR Autofocus.the 1994 6th IEEE Digital Signal Processing Workshop,Yosemite California,Oct.1994:53-56.
[31]雷万明,胡学成,倪晋麟.基于PGA的多普勒调频斜率估计.电子学报,2004,Vol.32.No.6:1017-1019.
[32]刘月花,荆麟角.对比度最优自聚焦算法.电子与信息学报,Vol.25.No.1.2003:24-29
[33]邓云凯,王宇,杨贤林,张志敏.基于对比度最优准则的自聚焦优化算法研究.电子学报,2006,Vol.34.No.9:1742-1744.
[34]Berizzi,F.;Corsini,G.;Diani,M.,et al.Autofocus of wide azimuth angle SAR images by contrast optimization.IGARRS'96.27-31 May 1996,Vol.2:1230-1232.
[35]王宏禹.非平稳随机信号分析与处理.北京,国防工业出版社,1999.
[36]Xu Chunguang,Gao Xinbo,Xie Weixin.LOCALIZED RADON-WIGNER TRANSFORM AND GENERALIZED-MARGINAL TIME-FREQUENCY DISTRIBUTIONS.JOURNAL OF ELECTRONICS,April 2000,Vol.17 No.2:116-122.
[37]洪涛.维格纳-威利分布与Radon-Wigner变换在信号时-频分析中的应用研究:[硕士学位论文].长春理工大学,2003.
[38]李艳,肖怀铁,付强.Radon-Wigner变换改进算法在多目标分辨及参数估计中的应用.电光与控制,2006,Vol.13.No.3:11-14.
[39]Xiang-Gen Xia.Discrete Chirp-Fourier Transform and Its Application to Chirp Rate Estimation.IEEE Trans.on Signal Processing,2000,48(11):3122-3133.
[40]Xin Guo,Hong-Bo Sun,Sheng-Li Wang,et al.Comments on discrete chirp-Fourier transform and its application to chirp rate estimation.IEEE Trans.on Signal Processing,2002,50(12):3115.
[41]Li JunXian,Li PingPing,Pu JieXin.Doppler frequency parameters estimation for SAR imaging using a modified discrete chirp-Fourier transform.IEEE International Conference on Mechatronics and Automation,29 July-1 Aug.,2005,Vol.2:649-652.
[42]Wang Yinbo,Zhang Xiaoling,Gong Zhenqiang,et al.Comparison of doppler frequency rate estimators in bistatic airborne SAR and experimental results.Asian and Pacific Conference on Synthetic Aperture Radar,Huangshan,China,5-9 Nov.,2007:98-102.
[43]朱力,胡学成,林幼权.匹配傅里叶变换的SAR多普勒参数估计.中国电子科学研究院学报,2006,Vol.1.No.2:152-1
[2]张直中.机载和星载合成孔径雷达导论.北京,电子工业出版社,2004.
[3]皮亦鸣,杨建宇,付毓生,杨晓波.合成孔径雷达成像原理.成都,电子科技大学出版社,2007.
[4]Ian G.Cumming,Frank H.Wong著,洪文,胡东辉等译.合成孔径雷达成像--算法与实现.北京,电子工业出版社,2007.
[5]保铮,邢孟道,王彤.雷达成像技术.北京,电子工业出版社,2005.
[6]张直中.双基地合成孔径雷达.现代雷达.2005.1.Vol.7 No.1:1-6.
[7]Horne,A.M.Yates,G.Bistatic Synthetic Aperture Radar.Proceedings of Radar 2002Conference,Edinburgh,Scotland Oct.2002.IEE publication No.490:6-10.
[8]J.H.G.Ender.A step To Bistatic SAR Processing.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May 25-27,2004:359-364.
[9]Ender,J.H.G.Signal Theoretical Aspects of Bistatic SAR.IEEE International Geoscience and Remote Sensing Symposium,Tolouse,July 2003:1438-1441.
[10]Otmar Loffeld,Holger Nies.Bistatic SAR Some Reflections on Rocca's Smile.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May 25-27,2004:379-383.
[11]I Walterscheid,A.B.R.Brenner,J.H.G.Ender.Geometry and System Aspects for a Bistatic Airborne SAR-Experiment.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May25-27,2004:567-570.
[12]Pascale Dubois-Fernandez,Hubert Cantalloube.Analysis of Bistatic Scattering behavior of natural surfaces.5th European Conference on Synthetic Aperture Radar,Neu-Ulm,Germany,May 25-27,2004.
[13]G.Yates,A.M.Horne,A.P.Blake,R.Middleton,D.B.Andre.Bistatic SAR image formation.5th European Conference on Synthetic Aperture Radar,2004:208-213.
[14]D.D'Aria,A.Monti Guarnieri,F.Rocca.FocusingBistatic Synthetic Aperture Radar Using Dip Move Out.IEEE Trans.On Geoscience and Remote Sensing,2004,42(7):1362-1376.
[15]H.Cantalloube,et al.Challenges in SAR processing for airborne bistatic acquisitions.5th European Conference on Synthetic Aperture radar,2004:577-580.
[16]Joachim H.G.Ender,I.Walterscheid,Andreas R.Brenner.New aspects of bistatic SAR:processing and experiments.Anchorage,USA,IGARSS 2004,Vol.3:1758-1762.
[17]Moccia A.,Rufino G.,D'Errico M.,et al.BISSAT:a bistatic SAR for Earth observation.IGARSS '02,2002,Vol.5:2628 -2630.
[18]况凌,沈晓峰,杨万麟.机载双基地SAR成像算法比较.电子学报,2006,Vol.34No.12:3211-3214.
[19]Huang Yan,Li Chunsheng,Li Jingwen.An airborne squint SAR processing algorithm.CIE International Conference of Radar 1996,8-10 Oct.1996:334 - 337.
[20]Yulong Shao,Zhaoda Zhu.Squint mode airborne SAR processing using RD algorithm.IEEE 1997 National Aerospace and Electronics Conference,14-17 July 1997,Vol.2:1025 - 1029.
[21]Chang C.Y.,Jin M.,Curlander J.C.Squint Mode SAR Processing Algorithms.IGARSS'89,10-14 Jul.1989,Vol.3:1702 - 1706.
[22]Xian Li,Xiong Jintao,Huang Yulin,Yang Jianyu.Research on Airborne Bistatic SAR Squint Imaging Mode Algorithm and Experiment Data Processing.APSAR2007.5-9 Nov.,2007,Huangshan:618-621.
[23]刘锐.机载双站SAR同步误差分析及仿真:[硕士学位论文].电子科技大学,2006.
[24]赵志钦,刘醒凡,顾德仁.SAR多卜勒参数的时域估计.信号处理,1995,Vol.11No.1:26-30.
[25]刘国庆,黄顺吉.星载SAR多普勒质心估计的改进方法.信号处理,1994,Vol.10.No.3:156-160.
[26]Nies H.,Loffeld O.,Natroshvili K,et al.Parameter estimation for bistatic constellations.IGARSS'05,25-29 Jul.2005,Vol.2:1038-1042.
[27]Samczynski Piotr,Kulpa Krzysztof.Concept of the Coherent Autofocus Map-Drift Technique.IRS 2006,24-26 May 2006:1-4.
[28]Prodi F.,Vinelli F.,Dente,F.An autofocusing technique of SAR data based on superresolution.IGARS S'93.18-21 Aug.1993,Vol.4:1586-1588.
[29]陈琦,李景文.相位梯度自聚焦算法的性能分析及改进.北京航空航天大学学报,2004,Vol.30.No.2:131-134.
[30]D.E.Whal,D.C.Ghiglia,C.V.Jakowatz.A new approach to Stripmap SAR Autofocus.the 1994 6th IEEE Digital Signal Processing Workshop,Yosemite California,Oct.1994:53-56.
[31]雷万明,胡学成,倪晋麟.基于PGA的多普勒调频斜率估计.电子学报,2004,Vol.32.No.6:1017-1019.
[32]刘月花,荆麟角.对比度最优自聚焦算法.电子与信息学报,Vol.25.No.1.2003:24-29
[33]邓云凯,王宇,杨贤林,张志敏.基于对比度最优准则的自聚焦优化算法研究.电子学报,2006,Vol.34.No.9:1742-1744.
[34]Berizzi,F.;Corsini,G.;Diani,M.,et al.Autofocus of wide azimuth angle SAR images by contrast optimization.IGARRS'96.27-31 May 1996,Vol.2:1230-1232.
[35]王宏禹.非平稳随机信号分析与处理.北京,国防工业出版社,1999.
[36]Xu Chunguang,Gao Xinbo,Xie Weixin.LOCALIZED RADON-WIGNER TRANSFORM AND GENERALIZED-MARGINAL TIME-FREQUENCY DISTRIBUTIONS.JOURNAL OF ELECTRONICS,April 2000,Vol.17 No.2:116-122.
[37]洪涛.维格纳-威利分布与Radon-Wigner变换在信号时-频分析中的应用研究:[硕士学位论文].长春理工大学,2003.
[38]李艳,肖怀铁,付强.Radon-Wigner变换改进算法在多目标分辨及参数估计中的应用.电光与控制,2006,Vol.13.No.3:11-14.
[39]Xiang-Gen Xia.Discrete Chirp-Fourier Transform and Its Application to Chirp Rate Estimation.IEEE Trans.on Signal Processing,2000,48(11):3122-3133.
[40]Xin Guo,Hong-Bo Sun,Sheng-Li Wang,et al.Comments on discrete chirp-Fourier transform and its application to chirp rate estimation.IEEE Trans.on Signal Processing,2002,50(12):3115.
[41]Li JunXian,Li PingPing,Pu JieXin.Doppler frequency parameters estimation for SAR imaging using a modified discrete chirp-Fourier transform.IEEE International Conference on Mechatronics and Automation,29 July-1 Aug.,2005,Vol.2:649-652.
[42]Wang Yinbo,Zhang Xiaoling,Gong Zhenqiang,et al.Comparison of doppler frequency rate estimators in bistatic airborne SAR and experimental results.Asian and Pacific Conference on Synthetic Aperture Radar,Huangshan,China,5-9 Nov.,2007:98-102.
[43]朱力,胡学成,林幼权.匹配傅里叶变换的SAR多普勒参数估计.中国电子科学研究院学报,2006,Vol.1.No.2:152-1