基于方位向尺度变换的聚束SAR成像算法研究
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摘要
合成孔径雷达(Synthetic Aperture Radar, SAR)聚束模式是一种高分辨率成像模式,但随着合成孔径长度增加和分辨率提高,目标的越分辨单元走动(Migration Through Range Cell, MTRC)也随之加剧,造成图像失真、散焦,限制了高分辨率成像区域的大小。信号格式是大场景高分辨率成像的关键。本文对聚束模式经典算法极坐标格式算法(Polar Format Algorithm, PFA)进行讨论,从信号格式角度分析了PFA中距离弯曲对高分辨率成像区域大小的限制,并给出补偿距离弯曲的一般方法,但距离弯曲的空变性使得补偿复杂且运算量大。距离徙动算法(Range Migration Algorithm, RMA)是另一种得到广泛应用的聚束模式成像算法。从信号格式角度看,RMA能够得到理想信号格式完全补偿MTRC,具有高分辨率大场景成像能力。然而,RMA处理的信号在方位向包含方位线性调频,要求雷达系统有很高的沿航迹采样率,降低了算法计算效率。
本文重点讨论的大场景极坐标格式算法(Widefield Polar Format Algorithm, WPFA)、Stolt极坐标算法(Stolt Polar Algorithm, SPA)、差分多普勒算法(Differential Doppler Algorithm, DDA)和雷达勘测处理算法(Radar Survey Processor Algorithm, RSP)是方位向尺度变换(Along-Track Alignment and Format System, ATAFS)结合传统的信号处理方法得到的新的成像算法。ATAFS是对信号相位历史存放格式进行空变校正避免距离弯曲的方法,这令高分辨率大场景成像成为可能。WPFA、SPA和DDA完全补偿了MTRC,信号格式都是理想的,具有高分辨率、大场景成像能力。RSP能够应用于实时成像处理中。与RMA相比,基于ATAFS的大场景成像算法计算效率有了很大提高,本文给出了ATAFS提高计算效率的实现方法:修正ATAFS参考函数将这四种算法应用于处理两维Dechirp解调运动补偿到中心点信号,以及对信号方位向抽取降低方位向采样率的方法来减小信号数据量。最后本文实现了基于ATAFS的大场景成像算法在实测数据处理中的应用。
The spotlight mode SAR, which can obtain extremely fine azimuth resolution, is an important imaging mode of SAR. However, the MTRC soars severely with wider azimuth angular interval and finer resolution, which causes distortion and defocusing in SAR image that limit useful scene size. Data formatting is a critical element in a fine-resolution SAR image formation processor. In this dissertation, the presence of range curvature distortion in conventional PFA is analyzed from data format perspective. RMA,another common choice for producing fine resolution imagery in spotlight mode besides PFA, is potentially the ideal algorithm for fine-resolution SAR imaging of large scenes, because it does not suffer range curvature distortion. A disadvantage of the RMA is that the RMA must operate on azimuth chirped signal data, which leads to an unnecessarily high along-track sampling rate for SAR system.
WPFA, SPA, DDA and RSP are four novel algorithms, which use the Along-Track Alignment and Format System (ATAFS) in conjunction with conventional data processing stages. ATAFS introduces a spatially-variant modification of the SAR phase history storage format, which enable full image quality over large scenes without range curvature distortion or image defocus. WPFA, SPA and DDA, which avoid range curvature distortion using ATAFS and coordinate transformation, complete the MTRC correction. These three algorithms process data into the ideal format, with the potential for fine-resolution SAR imaging of large scenes. Requiring no interpolation, RSP has a computational burden compatible with real-time survey or field processing. To be more efficient and less storage, the reference function of ATAFS is modified in order to operate on data stabilized to a fixed reference point, and the data is resampled at lower azimuth sample rate, which are presented in this dissertation. Furthermore, WPFA is applied to the real data case and data processing result is provided.
本文重点讨论的大场景极坐标格式算法(Widefield Polar Format Algorithm, WPFA)、Stolt极坐标算法(Stolt Polar Algorithm, SPA)、差分多普勒算法(Differential Doppler Algorithm, DDA)和雷达勘测处理算法(Radar Survey Processor Algorithm, RSP)是方位向尺度变换(Along-Track Alignment and Format System, ATAFS)结合传统的信号处理方法得到的新的成像算法。ATAFS是对信号相位历史存放格式进行空变校正避免距离弯曲的方法,这令高分辨率大场景成像成为可能。WPFA、SPA和DDA完全补偿了MTRC,信号格式都是理想的,具有高分辨率、大场景成像能力。RSP能够应用于实时成像处理中。与RMA相比,基于ATAFS的大场景成像算法计算效率有了很大提高,本文给出了ATAFS提高计算效率的实现方法:修正ATAFS参考函数将这四种算法应用于处理两维Dechirp解调运动补偿到中心点信号,以及对信号方位向抽取降低方位向采样率的方法来减小信号数据量。最后本文实现了基于ATAFS的大场景成像算法在实测数据处理中的应用。
The spotlight mode SAR, which can obtain extremely fine azimuth resolution, is an important imaging mode of SAR. However, the MTRC soars severely with wider azimuth angular interval and finer resolution, which causes distortion and defocusing in SAR image that limit useful scene size. Data formatting is a critical element in a fine-resolution SAR image formation processor. In this dissertation, the presence of range curvature distortion in conventional PFA is analyzed from data format perspective. RMA,another common choice for producing fine resolution imagery in spotlight mode besides PFA, is potentially the ideal algorithm for fine-resolution SAR imaging of large scenes, because it does not suffer range curvature distortion. A disadvantage of the RMA is that the RMA must operate on azimuth chirped signal data, which leads to an unnecessarily high along-track sampling rate for SAR system.
WPFA, SPA, DDA and RSP are four novel algorithms, which use the Along-Track Alignment and Format System (ATAFS) in conjunction with conventional data processing stages. ATAFS introduces a spatially-variant modification of the SAR phase history storage format, which enable full image quality over large scenes without range curvature distortion or image defocus. WPFA, SPA and DDA, which avoid range curvature distortion using ATAFS and coordinate transformation, complete the MTRC correction. These three algorithms process data into the ideal format, with the potential for fine-resolution SAR imaging of large scenes. Requiring no interpolation, RSP has a computational burden compatible with real-time survey or field processing. To be more efficient and less storage, the reference function of ATAFS is modified in order to operate on data stabilized to a fixed reference point, and the data is resampled at lower azimuth sample rate, which are presented in this dissertation. Furthermore, WPFA is applied to the real data case and data processing result is provided.
引文
[1] 张澄波等,综合孔径雷达原理、系统分析与应用,科学出版社,1989。
[2] Carl A. Wiley, Synthetic Aperture Radars, IEEE Trans. On AES, Vol.21, No.3, pp.440-443, May 1985.
[3] W. G. Carrara, R. S. Goodman, R. M. Majewski, Spotlight Synthetic Aperture Radar: Signal Processing Algorithms, Artech House, Boston, 1995.
[4] 肖靖,聚束SAR极坐标格式算法研究,南京航空航天大学硕士学位论文,2004。
[5] 程玉平,SAR成像中几个问题的研究,西安电子科技大学博士学位论文,2000。
[6] W. G. Carrara, R. S. Goodman, M. A. Ricoy, New Algorithms for Wieldfield SAR Image Formation, 2004. Proceedings of the IEEE, Radar Conference, 26-29 April 2004 Page(s):38-43.
[7] 李琛,聚束模式SAR大场景成像算法研究,南京航空航天大学硕士学位论文,2006。
[8] Cafforio, C., C. Prati, F. Rocca, “SAR Data Focusing Using Seimic Migration Techniques,” IEEE Transaction on Aerospace and Electronic Systems, Vol.27, No.2, March 1991, Page(s): 194-206.
[9] C. Prati, A. Monti Guarnieri, F. Rocca, “Spot Mode SAR Focusing with the ω ? k Technique,” Geoscience and Remote Sensing Symposium, 1991. IGARSS’91. ‘Remote Sensing: Global Monitoring for Earth Management’. International, Volume 2, June 3-6, 1991, Page(s): 631-634.
[10] D.C. Munson, J.D. O'Brien, and W.K. Jenkins, A Tomographic Formulation of Spotlight-Mode Synthetic Aperture Radar, Processing of the IEEE, Vol.72,No.8,August19 83,pp.917-925.
[11] M.D. Desai, and W.K. Jenkins, Convolutional Backprojection Image Reconstruction for Spotlight Mode Synthetic Aperture Radar, IEEE Transactions on Image Processing. Vol.1,N o.4,October1992,pp .50 5- 517.
[12] 孙进平,机载聚束模式合成孔径雷达的成像算法研究,北京航空航天大学博士学位论文,2001。
[13] N. E .Doren,Space-Variant Post-Filtering for Wavefront Curvature Correction in PolarFormatted Spotlight-Mode SAR Imagery, Dissertation for the Degree of Doctor of Philosophy Engineering, Albuquerque New Mexico, the University of New Mexico, Dec. 1999.
[14] W. G. Carrara, R. S. Goodman, M. A. Ricoy, “New Algorithms for Wieldfield SAR Image Formation,” 2004. Proceedings of the IEEE, Radar Conference, 26-29 April 2004 Page(s):38-43.
[15] Yong Li, Daiyin Zhu, Zhaoda Zhu, “Geometric Distortion Correction in the Subaperture Processing for Hight Squint Aireborne SAR Imaging,” Geoscience and Remote Sencing Symposium, 2004. IGARSS’04. Proceedings. 2004 IEEE International, Volume 6 Page(s): 3919-3922 vol.6.
[16] W. G. Carrara, R. S. Goodman, M. A. Ricoy, Method and System for Providing Along-Track Alignment and Formatting of Synthetic Aperture Radar(SAR) Data and SAR Image Formation Algorithms Using Such Method and System, United States, US 6,873,285 B2, Mar.29, 2005.
[17] 袁远能,机载聚束式合成孔径雷达聚焦算法研究,北京航空航天大学博士后士学位论文,2001。
[18] J. E. Maisel, R. E. Morden, “Rotation of a Two-Dimensional Sampling Set Using One-Dimensional Resampling,” IEEE, Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-29, NO.6, December, 1981.
[19] Frank H. Wong and Tat Soon Yeo, A Novel Technique for the Processing of Short-Dwell Spotlight SAR Data, IEEE Transactions on Geoscience and Remote Sensing, Vol. 41, NO. 5, May, 2003.
[20] 武昕伟,朱兆达,基于聚束照射SAR成像算法的条带SAR数据处理,南京航空航天大学学报,第34卷第5期,2002。
[21] J.C. Curlander, et al., Synthetic Aperture Radar System and Signal Processing. John Wiley & Sons, INC., 1991.
[22] Aushrman D.A., et al., Developments in Radar Imaging, IEEE Trans. on AES, 1984, Page(s): 363-381.
[23] 禹卫东,合成孔径雷达信号处理,南京航空航天大学博士学位论文,1997。
[24] D.T. Cobra, A.v.Oppenheim, J.S. Jaffe, Geometric Distortions in Side-Scan Sonar Image: A Procedure for Their Estimation and Correction, Oceanic Engineering, IEEE, Vol 17,1992, Page(s): 252-268.
[25] A. Goshtasby, Registration of Images with Geometric distortions, Geosicence and Remote Sensing, Vol 26, 1988 Page(s): 60-64.
[26] N. J. S. Stacy, “Range Cell Migration in the Spotlight SAR Polar Format Algorithm,” Geoscience and Remote Sencing Symposium, 2000. Proceedings. IGARSS 2000. IEEE 2000 International, Volume 5 Page(s): 2275-2277 vol.5.
[27] 刘永坦等,雷达成像技术,哈尔滨工业大学出版社,1999。
[28] Raney. R.K., A New and Foundamental Fourier Transform Pair, Geosicence and Remote Sensing Symposim, 1992. IGARSS’92. International, 1992, Page(s): 106-107.
[29] F. M. Seifert, J. R. Moreira, W. Keydel, A. Moreira, Determination of Phase Errors in Spaceborne SAR, Geosicence and Remote Sensing Symposim, 1993. IGARSS’93. International, 1993, Page(s): 791-793.
[30] Gazdag, J., P. Sguazzero, “Migration of Seimic Data,” Proceeding of the IEEE, Vol.72, No.10, Oct 1984, Page(s): 1302-1315.
[2] Carl A. Wiley, Synthetic Aperture Radars, IEEE Trans. On AES, Vol.21, No.3, pp.440-443, May 1985.
[3] W. G. Carrara, R. S. Goodman, R. M. Majewski, Spotlight Synthetic Aperture Radar: Signal Processing Algorithms, Artech House, Boston, 1995.
[4] 肖靖,聚束SAR极坐标格式算法研究,南京航空航天大学硕士学位论文,2004。
[5] 程玉平,SAR成像中几个问题的研究,西安电子科技大学博士学位论文,2000。
[6] W. G. Carrara, R. S. Goodman, M. A. Ricoy, New Algorithms for Wieldfield SAR Image Formation, 2004. Proceedings of the IEEE, Radar Conference, 26-29 April 2004 Page(s):38-43.
[7] 李琛,聚束模式SAR大场景成像算法研究,南京航空航天大学硕士学位论文,2006。
[8] Cafforio, C., C. Prati, F. Rocca, “SAR Data Focusing Using Seimic Migration Techniques,” IEEE Transaction on Aerospace and Electronic Systems, Vol.27, No.2, March 1991, Page(s): 194-206.
[9] C. Prati, A. Monti Guarnieri, F. Rocca, “Spot Mode SAR Focusing with the ω ? k Technique,” Geoscience and Remote Sensing Symposium, 1991. IGARSS’91. ‘Remote Sensing: Global Monitoring for Earth Management’. International, Volume 2, June 3-6, 1991, Page(s): 631-634.
[10] D.C. Munson, J.D. O'Brien, and W.K. Jenkins, A Tomographic Formulation of Spotlight-Mode Synthetic Aperture Radar, Processing of the IEEE, Vol.72,No.8,August19 83,pp.917-925.
[11] M.D. Desai, and W.K. Jenkins, Convolutional Backprojection Image Reconstruction for Spotlight Mode Synthetic Aperture Radar, IEEE Transactions on Image Processing. Vol.1,N o.4,October1992,pp .50 5- 517.
[12] 孙进平,机载聚束模式合成孔径雷达的成像算法研究,北京航空航天大学博士学位论文,2001。
[13] N. E .Doren,Space-Variant Post-Filtering for Wavefront Curvature Correction in PolarFormatted Spotlight-Mode SAR Imagery, Dissertation for the Degree of Doctor of Philosophy Engineering, Albuquerque New Mexico, the University of New Mexico, Dec. 1999.
[14] W. G. Carrara, R. S. Goodman, M. A. Ricoy, “New Algorithms for Wieldfield SAR Image Formation,” 2004. Proceedings of the IEEE, Radar Conference, 26-29 April 2004 Page(s):38-43.
[15] Yong Li, Daiyin Zhu, Zhaoda Zhu, “Geometric Distortion Correction in the Subaperture Processing for Hight Squint Aireborne SAR Imaging,” Geoscience and Remote Sencing Symposium, 2004. IGARSS’04. Proceedings. 2004 IEEE International, Volume 6 Page(s): 3919-3922 vol.6.
[16] W. G. Carrara, R. S. Goodman, M. A. Ricoy, Method and System for Providing Along-Track Alignment and Formatting of Synthetic Aperture Radar(SAR) Data and SAR Image Formation Algorithms Using Such Method and System, United States, US 6,873,285 B2, Mar.29, 2005.
[17] 袁远能,机载聚束式合成孔径雷达聚焦算法研究,北京航空航天大学博士后士学位论文,2001。
[18] J. E. Maisel, R. E. Morden, “Rotation of a Two-Dimensional Sampling Set Using One-Dimensional Resampling,” IEEE, Transactions on Acoustics, Speech, and Signal Processing, Vol. ASSP-29, NO.6, December, 1981.
[19] Frank H. Wong and Tat Soon Yeo, A Novel Technique for the Processing of Short-Dwell Spotlight SAR Data, IEEE Transactions on Geoscience and Remote Sensing, Vol. 41, NO. 5, May, 2003.
[20] 武昕伟,朱兆达,基于聚束照射SAR成像算法的条带SAR数据处理,南京航空航天大学学报,第34卷第5期,2002。
[21] J.C. Curlander, et al., Synthetic Aperture Radar System and Signal Processing. John Wiley & Sons, INC., 1991.
[22] Aushrman D.A., et al., Developments in Radar Imaging, IEEE Trans. on AES, 1984, Page(s): 363-381.
[23] 禹卫东,合成孔径雷达信号处理,南京航空航天大学博士学位论文,1997。
[24] D.T. Cobra, A.v.Oppenheim, J.S. Jaffe, Geometric Distortions in Side-Scan Sonar Image: A Procedure for Their Estimation and Correction, Oceanic Engineering, IEEE, Vol 17,1992, Page(s): 252-268.
[25] A. Goshtasby, Registration of Images with Geometric distortions, Geosicence and Remote Sensing, Vol 26, 1988 Page(s): 60-64.
[26] N. J. S. Stacy, “Range Cell Migration in the Spotlight SAR Polar Format Algorithm,” Geoscience and Remote Sencing Symposium, 2000. Proceedings. IGARSS 2000. IEEE 2000 International, Volume 5 Page(s): 2275-2277 vol.5.
[27] 刘永坦等,雷达成像技术,哈尔滨工业大学出版社,1999。
[28] Raney. R.K., A New and Foundamental Fourier Transform Pair, Geosicence and Remote Sensing Symposim, 1992. IGARSS’92. International, 1992, Page(s): 106-107.
[29] F. M. Seifert, J. R. Moreira, W. Keydel, A. Moreira, Determination of Phase Errors in Spaceborne SAR, Geosicence and Remote Sensing Symposim, 1993. IGARSS’93. International, 1993, Page(s): 791-793.
[30] Gazdag, J., P. Sguazzero, “Migration of Seimic Data,” Proceeding of the IEEE, Vol.72, No.10, Oct 1984, Page(s): 1302-1315.