分布式星载雷达回波特性分析与仿真
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摘要
分布式星载雷达是由一簇编队飞行的小卫星构成的稀疏阵列雷达,簇内各小卫星雷达协同工作,形成一个更大、更复杂的虚拟卫星雷达。不仅具有单星雷达的覆盖范围广、全天候、全天时等优点,更因其具有多个天线孔径和更长的基线,能够探测地面上低速运动目标。但分布式星载雷达轨道高度较高,小卫星速度较大,以及稀疏孔径所引入的栅瓣,使得对地面低速动目标的检测困难重重。
为了实现地杂波的抑制和低速动目标的检测,本论文围绕着分布式星载雷达存在的主要问题及地杂波空时特性进行了研究,主要内容如下。
在分布式星载雷达的观测几何方面,确定了观测中所涉及的三个坐标系,以及它们之间相互变换的关系式,研究了观测区域中地杂波散射单元的划分,最终确立了分布式星载雷达的地杂波的观测几何模型,并通过仿真分析验证所建模型的正确性。该模型为研究分布式星载雷达地杂波空时特性以及低速动目标的检测提供了基础。
在介绍一般雷达地杂波生成机理的基础上,研究了分布式星载雷达地杂波存在的主要问题,相对于卫星平台,地球本身一直在自转,而地球的自转会在回波的多普勒频率中引入偏航角和偏航幅度。由于分布式星载雷达观测区域比较大,以及卫星轨道高度较高,地杂波存在距离模糊。而较大卫星平台速度,使得多普勒域也存在模糊。簇内小卫星之间间距远大于半波长,空间的欠采样使接收天线方向图中存在栅瓣。
最后,在分析分布式星载雷达地杂波协方差阵、功率谱、杂波迹的基础上,研究了在分布式星载雷达中地杂波的空时二维特性。理论和仿真结果表明:地球的自转会产生仅与轨道倾角和星下点纬度相关的偏航角和偏航幅度,同时地球自转使得角度-多普勒迹发生弯曲。距离模糊时不同距离环上的散射单元相互叠加,使地杂波距离-多普勒谱展宽。多普勒模糊使地杂波的角度-多普勒分散开来。栅瓣的存在使分布式星载雷达地杂波中产生受天线方向图调制的主杂波分布。
Distributed Spacborne Radar is a sparse array radar formed by a cluster of microsatellites flying in formation, Those microsatellites through collaborative work form a larger and more complex dummy satellite radar. With the advantage of single satellite radar, such as covering large scope, working all-weather and all-time and so on, Distributed Spacborne Radar can detect low speed ground target, because of its multi-aperture and longer base-line. Unfortunately, using Distributed Spacborne Radar to detect moving target faces many difficulties made by the higher orbit altitude, larger microsatellite speed, and gratinglobes coming with sparse antenna aperture.
To suppress ground clutter and detect low speed moving target, the main issue of ground clutter and the ground clutter space-time characteristics in Distributed Spacborne Radar is studied in this dissertation, the main contents are as follows.
In terms of the observation geometry of Distributed Spacborne Radar, five coordinate systems involving in the observation geometry are established first, and their mutual transformational relation are analyzed. Then the partition of range bins in observation region is studied, and establish the observation geometry model of Distributed Spacborne Radar finally, the established model is examined correct through simulations and analysis. The model is a foundation of studying the space-time characteristics of ground clutter and detecting of low speed moving target in Distributed Spacborne Radar.
After the introduction of originates of common radar ground clutter, the main issues of the ground clutter in Distributed Spacborne Radar are studied. The earth is rotating all the time according to microsatellites, crab angle and crab magnitude come with the earth’s rotation in the Doppler frequency of the return signals. Because of the larger observation region of the Distributed Spacborne Radar and the higher altitude of the microsatellite orbit, range ambiguities occur in the ground clutter. Also, the larger speed of microsatellite platform result in Doppler ambiguities in Distributed Spacborne Radar. The length between microsatellites is much bigger than half of wavelength, the low sample frequency in space results in gratinglobes in receiving antenna.
Finally, on the foundation of the analysis of the clutter covariance matrix, power spectrum, clutter ridges of Distributed Spacborne Radar, the space-time characteristics of the ground clutter in Distributed Spacborne Radar are studied in detail. Theoretical analysis and simulation results show that: the clutter rank becomes bigger along with the crab angle brought by the earth’s rotation, and the angle-doppler trace is changed a curve from a straight by earth’s rotation. When range ambiguities happen, return signals from different range bins add together, and the width of ground clutter spectrum is made larger by range ambiguities. The clutter rank is made lager by the doppler ambiguities, also doppler ambiguities cause the clutter spectrum dispersed. Gratinglobes bring gratinglobes clutter modulated by the receive antenna.
为了实现地杂波的抑制和低速动目标的检测,本论文围绕着分布式星载雷达存在的主要问题及地杂波空时特性进行了研究,主要内容如下。
在分布式星载雷达的观测几何方面,确定了观测中所涉及的三个坐标系,以及它们之间相互变换的关系式,研究了观测区域中地杂波散射单元的划分,最终确立了分布式星载雷达的地杂波的观测几何模型,并通过仿真分析验证所建模型的正确性。该模型为研究分布式星载雷达地杂波空时特性以及低速动目标的检测提供了基础。
在介绍一般雷达地杂波生成机理的基础上,研究了分布式星载雷达地杂波存在的主要问题,相对于卫星平台,地球本身一直在自转,而地球的自转会在回波的多普勒频率中引入偏航角和偏航幅度。由于分布式星载雷达观测区域比较大,以及卫星轨道高度较高,地杂波存在距离模糊。而较大卫星平台速度,使得多普勒域也存在模糊。簇内小卫星之间间距远大于半波长,空间的欠采样使接收天线方向图中存在栅瓣。
最后,在分析分布式星载雷达地杂波协方差阵、功率谱、杂波迹的基础上,研究了在分布式星载雷达中地杂波的空时二维特性。理论和仿真结果表明:地球的自转会产生仅与轨道倾角和星下点纬度相关的偏航角和偏航幅度,同时地球自转使得角度-多普勒迹发生弯曲。距离模糊时不同距离环上的散射单元相互叠加,使地杂波距离-多普勒谱展宽。多普勒模糊使地杂波的角度-多普勒分散开来。栅瓣的存在使分布式星载雷达地杂波中产生受天线方向图调制的主杂波分布。
Distributed Spacborne Radar is a sparse array radar formed by a cluster of microsatellites flying in formation, Those microsatellites through collaborative work form a larger and more complex dummy satellite radar. With the advantage of single satellite radar, such as covering large scope, working all-weather and all-time and so on, Distributed Spacborne Radar can detect low speed ground target, because of its multi-aperture and longer base-line. Unfortunately, using Distributed Spacborne Radar to detect moving target faces many difficulties made by the higher orbit altitude, larger microsatellite speed, and gratinglobes coming with sparse antenna aperture.
To suppress ground clutter and detect low speed moving target, the main issue of ground clutter and the ground clutter space-time characteristics in Distributed Spacborne Radar is studied in this dissertation, the main contents are as follows.
In terms of the observation geometry of Distributed Spacborne Radar, five coordinate systems involving in the observation geometry are established first, and their mutual transformational relation are analyzed. Then the partition of range bins in observation region is studied, and establish the observation geometry model of Distributed Spacborne Radar finally, the established model is examined correct through simulations and analysis. The model is a foundation of studying the space-time characteristics of ground clutter and detecting of low speed moving target in Distributed Spacborne Radar.
After the introduction of originates of common radar ground clutter, the main issues of the ground clutter in Distributed Spacborne Radar are studied. The earth is rotating all the time according to microsatellites, crab angle and crab magnitude come with the earth’s rotation in the Doppler frequency of the return signals. Because of the larger observation region of the Distributed Spacborne Radar and the higher altitude of the microsatellite orbit, range ambiguities occur in the ground clutter. Also, the larger speed of microsatellite platform result in Doppler ambiguities in Distributed Spacborne Radar. The length between microsatellites is much bigger than half of wavelength, the low sample frequency in space results in gratinglobes in receiving antenna.
Finally, on the foundation of the analysis of the clutter covariance matrix, power spectrum, clutter ridges of Distributed Spacborne Radar, the space-time characteristics of the ground clutter in Distributed Spacborne Radar are studied in detail. Theoretical analysis and simulation results show that: the clutter rank becomes bigger along with the crab angle brought by the earth’s rotation, and the angle-doppler trace is changed a curve from a straight by earth’s rotation. When range ambiguities happen, return signals from different range bins add together, and the width of ground clutter spectrum is made larger by range ambiguities. The clutter rank is made lager by the doppler ambiguities, also doppler ambiguities cause the clutter spectrum dispersed. Gratinglobes bring gratinglobes clutter modulated by the receive antenna.
引文
[1]梁甸农,朱炬波,董臻.分布式小卫星雷达.中国基础科学.科学前沿2004,(07):7-10
[2] Hans Steykal,John K.Schindler,Peter Franchi. Pattern synthesis for TechSat21-A distributed space-based radar system.IEEE Antennas and Propagation Magazine,2003,45(4):19-25
[3] Daniel A.Leatherwood,William L.Melvin. Configuring a sparse aperture antenna for spaceborne MTI Radar.IEEE Radar Conference,2003,139-146
[4] S.Feng,J.Chen. Low-Angle reflectivity modeling of land clutter.IEEE Geoscience and Remote Sensing Letters,2006,3(2):254-258
[5] A D maio,A.Farina. Statistical tests for higher order analysis of radar clutter.IEEE Trans,2005, 41(1):205-218
[6] Sekine.M,Donald Weiner. Computer generation of correlated non-gaussian radar clutter.IEEE Trans,1995,31(1):106-115
[7] Sekine.M,Peebles.P. The generation of correlated lognormal clutter for radar simulation.IEEE Trans,1971,1215-1217
[8] J.V.Drfarnco,W.L.Rubin. Spatial ambiguity and resolution for array antenna system.IEEE Trans,1996,229-237
[9] M.V.Tollefson,B.K.Preiss. Space based radar constellation optimization.IEEE Aerospace conference,1998,397-388
[10] Tim J.Nohara.Comparison of DPCA and STAP for space-based radar.IEEE International Radar Conference,1995,113-119
[11] Troy L.Hacker,Raymond J.Sedwick,David W.Miller. Performance analysis of space-based GMTI radar system using separated spacecraft interferomenty.2000
[12] S.Unnikrishna Pillai,Braham Himed,Ke Yong Li. Effect of earth’s rotation and range foldover on space based radar performance.IEEE Radar Conference,2005,8(5):78-82
[13]陆必应,梁甸农.模糊对分布式天基稀疏孔径GMTI雷达的影响.现代雷达,2006,28(12):9-14
[14]王彤,保铮,廖桂生.天基分布式GMTI方法.电子学报,2006,34(3):399-403
[15]范海菊,李景文.星载PD雷达的地杂波模拟.雷达科学与技术.2006,6(2):339-343
[16]任太姝,李景文.天基雷达杂波谱估计及特性分析.雷达科学与技术,2007,5(5):324-330
[17]康雪艳,张云华,江碧涛.星载稀疏阵扫描模式干涉雷达动目标检测研究.测试技术学报,2007,21(3):195-199
[18]王文生,王小谟,许建峰.天基雷达地面回波的多普勒特性.北京理工大学学报, 2006,26(3):268-271
[19]云日升,张云华,江碧涛,康雪艳.星载稀疏孔径GMTI雷达STAP仿真研究.现代雷达,2006,28(6):14-18
[20] Leopold J.Cantafio. Space based radar handbook. Beijing: Publishing house of electronic industry
[21]张明友,汪学刚.雷达系统.北京:电子工业出版社,2006,33-35
[22] Davis M E. Space based radar moving detection challenge.IEE Conference Publication, 2002,2921-2924
[23] C.Bouvier,L.Martinet,M.Artaud. Radar clutter classification using autoregressive modeling, K-distribution and neural network.IEEE Trans,1995,1820-1823
[24] Zulch P,Davis M,Adzima L. The earth’s rotation effect on a LEO L-band GMTI SBR and mitigation strageies.IEEE Radar Conference,2004,27-31
[25] S.Unnikrishna Pillai,Braham Himed,Ke Yong Li. Modeling of earth’s rotation for space based radar.IEEE Radar Conference,2006,1682-1686
[26]王文生,王小谟.天基雷达的几个基本问题.现代雷达,2007,29(4):1-4
[27] Davis M E. Space based radar moving target dtection challenges. IEE Conference Publication, n490, 2002, 2921-2924.
[28] Richard A.Altes. Target position estimation in radar and sonar, and generalized ambiguity analysis for maximum likelihood parameter estimation.IEEE Trans,1991,67(6):920-930
[29] Klemm R. Ambiguities in bistatic STAP radar.IGARSS,2000:1009-1010
[30] Hua Li, Jun Tang, Yingning Peng. L-band SBR moving target detection in SAR-GMTI modes, IEEE 2004 Aerospace Conference Proceedings,2004, 2211-2219
[31] Raney R K. Doppler properties of radar in circular orbits[J]. International Journal of Remote Sensing,1986,7(9):1153-1162.
[32] Goodman N A.SAR and MTI Processing of sparse satellite clusters.Kansas: the University of Kansas,2002
[33] Godara L C.Handbook of antennas in wireless communication.NY:CRC Press,2002
[34]龚耀寰.自适应滤波-时域自适应滤波和智能天线.北京:电子工业出版社,2003
[35] K Marais and R.Sedwick. Space based GMTI using scanned pattern interferometric radar. IEEE Proceeding,2001,4:2047-2055
[36]陆必应,梁甸农.角度模糊对天基雷达稀疏孔径GMTI雷达的影响与抑制方法.电子学报.2007,35(3):501-505
[37] Kang X Y,Zhang Y H. Angle and doppler ambiguity mitigation for spaceborne sparse array GMTI radar.IEEE Trans,2009
[38] Adve R,Schneible R,Mcmillan R. Adaptive space/frequency processing for distributed aperture radar.IEEE Radar Conference,2003:160-164
[39] Klemm R.Space-time adaptive processing: Principles and Application.IEE Publishers, 1998:117-149
[40] Capon J.High-resolution frequency-wavenumber spectrum analysis.Proc IEEE,1969, 57:1408-1418
[41]伍勇,汤俊,彭应宁.线性稀疏阵雷达的杂波特性.清华大学学报,2008,48(1):50-54
[42] Himed B, Zhang Y H, Hajjari A. Stap with angle-doppler compensation for bistatic airborne radars. In Proceedings of IEEE 2002 National Radar Conference, RadarCon-02, (Long Beach, California, USA), 2002, 311-317
[2] Hans Steykal,John K.Schindler,Peter Franchi. Pattern synthesis for TechSat21-A distributed space-based radar system.IEEE Antennas and Propagation Magazine,2003,45(4):19-25
[3] Daniel A.Leatherwood,William L.Melvin. Configuring a sparse aperture antenna for spaceborne MTI Radar.IEEE Radar Conference,2003,139-146
[4] S.Feng,J.Chen. Low-Angle reflectivity modeling of land clutter.IEEE Geoscience and Remote Sensing Letters,2006,3(2):254-258
[5] A D maio,A.Farina. Statistical tests for higher order analysis of radar clutter.IEEE Trans,2005, 41(1):205-218
[6] Sekine.M,Donald Weiner. Computer generation of correlated non-gaussian radar clutter.IEEE Trans,1995,31(1):106-115
[7] Sekine.M,Peebles.P. The generation of correlated lognormal clutter for radar simulation.IEEE Trans,1971,1215-1217
[8] J.V.Drfarnco,W.L.Rubin. Spatial ambiguity and resolution for array antenna system.IEEE Trans,1996,229-237
[9] M.V.Tollefson,B.K.Preiss. Space based radar constellation optimization.IEEE Aerospace conference,1998,397-388
[10] Tim J.Nohara.Comparison of DPCA and STAP for space-based radar.IEEE International Radar Conference,1995,113-119
[11] Troy L.Hacker,Raymond J.Sedwick,David W.Miller. Performance analysis of space-based GMTI radar system using separated spacecraft interferomenty.2000
[12] S.Unnikrishna Pillai,Braham Himed,Ke Yong Li. Effect of earth’s rotation and range foldover on space based radar performance.IEEE Radar Conference,2005,8(5):78-82
[13]陆必应,梁甸农.模糊对分布式天基稀疏孔径GMTI雷达的影响.现代雷达,2006,28(12):9-14
[14]王彤,保铮,廖桂生.天基分布式GMTI方法.电子学报,2006,34(3):399-403
[15]范海菊,李景文.星载PD雷达的地杂波模拟.雷达科学与技术.2006,6(2):339-343
[16]任太姝,李景文.天基雷达杂波谱估计及特性分析.雷达科学与技术,2007,5(5):324-330
[17]康雪艳,张云华,江碧涛.星载稀疏阵扫描模式干涉雷达动目标检测研究.测试技术学报,2007,21(3):195-199
[18]王文生,王小谟,许建峰.天基雷达地面回波的多普勒特性.北京理工大学学报, 2006,26(3):268-271
[19]云日升,张云华,江碧涛,康雪艳.星载稀疏孔径GMTI雷达STAP仿真研究.现代雷达,2006,28(6):14-18
[20] Leopold J.Cantafio. Space based radar handbook. Beijing: Publishing house of electronic industry
[21]张明友,汪学刚.雷达系统.北京:电子工业出版社,2006,33-35
[22] Davis M E. Space based radar moving detection challenge.IEE Conference Publication, 2002,2921-2924
[23] C.Bouvier,L.Martinet,M.Artaud. Radar clutter classification using autoregressive modeling, K-distribution and neural network.IEEE Trans,1995,1820-1823
[24] Zulch P,Davis M,Adzima L. The earth’s rotation effect on a LEO L-band GMTI SBR and mitigation strageies.IEEE Radar Conference,2004,27-31
[25] S.Unnikrishna Pillai,Braham Himed,Ke Yong Li. Modeling of earth’s rotation for space based radar.IEEE Radar Conference,2006,1682-1686
[26]王文生,王小谟.天基雷达的几个基本问题.现代雷达,2007,29(4):1-4
[27] Davis M E. Space based radar moving target dtection challenges. IEE Conference Publication, n490, 2002, 2921-2924.
[28] Richard A.Altes. Target position estimation in radar and sonar, and generalized ambiguity analysis for maximum likelihood parameter estimation.IEEE Trans,1991,67(6):920-930
[29] Klemm R. Ambiguities in bistatic STAP radar.IGARSS,2000:1009-1010
[30] Hua Li, Jun Tang, Yingning Peng. L-band SBR moving target detection in SAR-GMTI modes, IEEE 2004 Aerospace Conference Proceedings,2004, 2211-2219
[31] Raney R K. Doppler properties of radar in circular orbits[J]. International Journal of Remote Sensing,1986,7(9):1153-1162.
[32] Goodman N A.SAR and MTI Processing of sparse satellite clusters.Kansas: the University of Kansas,2002
[33] Godara L C.Handbook of antennas in wireless communication.NY:CRC Press,2002
[34]龚耀寰.自适应滤波-时域自适应滤波和智能天线.北京:电子工业出版社,2003
[35] K Marais and R.Sedwick. Space based GMTI using scanned pattern interferometric radar. IEEE Proceeding,2001,4:2047-2055
[36]陆必应,梁甸农.角度模糊对天基雷达稀疏孔径GMTI雷达的影响与抑制方法.电子学报.2007,35(3):501-505
[37] Kang X Y,Zhang Y H. Angle and doppler ambiguity mitigation for spaceborne sparse array GMTI radar.IEEE Trans,2009
[38] Adve R,Schneible R,Mcmillan R. Adaptive space/frequency processing for distributed aperture radar.IEEE Radar Conference,2003:160-164
[39] Klemm R.Space-time adaptive processing: Principles and Application.IEE Publishers, 1998:117-149
[40] Capon J.High-resolution frequency-wavenumber spectrum analysis.Proc IEEE,1969, 57:1408-1418
[41]伍勇,汤俊,彭应宁.线性稀疏阵雷达的杂波特性.清华大学学报,2008,48(1):50-54
[42] Himed B, Zhang Y H, Hajjari A. Stap with angle-doppler compensation for bistatic airborne radars. In Proceedings of IEEE 2002 National Radar Conference, RadarCon-02, (Long Beach, California, USA), 2002, 311-317