Diversity considerations in wideband radar detection of migrating targets in clutter
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摘要
Wideband radars have been proposed for detection of moving targets, with unique capability of non-ambiguous detection due to range migration. Moreover, frequency diversity has long been used for mitigating the fading effects caused by target and clutter fluctuations. The real benefits of wideband radars are difficult to analyze, since they derive from the combined effects of target resolution in range, migration over successive cells of clutter, Doppler resolution and instantaneous bandwidth, and residual ambiguities in Doppler. In order to contribute to a better understanding of the benefits of agile transmissions for detection of moving targets, clutter cancelling performances of wideband radars are examined, demonstrating clear benefits from diversity on clutter and target, primarily – but not only – obtained through target migration effects. Special attention is given to long-range surveillance and tracking, and new results on detection of moving targets in clutter will be provided to demonstrate the effectiveness of these new architectures for small targets detection at long range, in difficult environments. Finally, recommendations for system designs that improve the discrimination of moving targets against fixed and diffuse clutter are presented.
Wideband radars have been proposed for detection of moving targets, with unique capability of non-ambiguous detection due to range migration. Moreover, frequency diversity has long been used for mitigating the fading effects caused by target and clutter fluctuations. The real benefits of wideband radars are difficult to analyze, since they derive from the combined effects of target resolution in range, migration over successive cells of clutter, Doppler resolution and instantaneous bandwidth, and residual ambiguities in Doppler. In order to contribute to a better understanding of the benefits of agile transmissions for detection of moving targets, clutter cancelling performances of wideband radars are examined, demonstrating clear benefits from diversity on clutter and target, primarily – but not only – obtained through target migration effects. Special attention is given to long-range surveillance and tracking, and new results on detection of moving targets in clutter will be provided to demonstrate the effectiveness of these new architectures for small targets detection at long range, in difficult environments. Finally, recommendations for system designs that improve the discrimination of moving targets against fixed and diffuse clutter are presented.
Wideband radars have been proposed for detection of moving targets, with unique capability of non-ambiguous detection due to range migration. Moreover, frequency diversity has long been used for mitigating the fading effects caused by target and clutter fluctuations. The real benefits of wideband radars are difficult to analyze, since they derive from the combined effects of target resolution in range, migration over successive cells of clutter, Doppler resolution and instantaneous bandwidth, and residual ambiguities in Doppler. In order to contribute to a better understanding of the benefits of agile transmissions for detection of moving targets, clutter cancelling performances of wideband radars are examined, demonstrating clear benefits from diversity on clutter and target, primarily – but not only – obtained through target migration effects. Special attention is given to long-range surveillance and tracking, and new results on detection of moving targets in clutter will be provided to demonstrate the effectiveness of these new architectures for small targets detection at long range, in difficult environments. Finally, recommendations for system designs that improve the discrimination of moving targets against fixed and diffuse clutter are presented.
引文
1 Le Chevalier F.Principles of Radar and Sonar Signal Processing.Norwood:Artech House,2002
2 De Maio A,Greco S.Modern Radar Detection Theory.Raleigh:SciTech Pub,2016
3 Richards M A,Scheer J A,Holm W A,et al.Principles of Modern Radar.Raleigh:SciTech Pub,2010
4 Le Chevalier F.Wideband wide beam motion sensing.In:Advanced Ultrawideband Radar:Targets,Signals and Applications.Boca Raton:CRC Press,2016
5 Cherniakov M.Bistatic Radar:Principles and Practice.Hoboken:Wiley,2007
6 Chernyak V.Fundamentals of Multisite Radar Systems.Boca Raton:CRC Press,1998
7 Bidon S,Lasserre M,Le Chevalier F.Bayesian sparse estimation of radar targets in the compressed sensing framework.In:Compressive Sensing of Earth Observations.Boca Raton:CRC Press,2017
8 Petrov N,Le Chevalier F,Bogdanovic N,et al.Range migrating target detection in correlated compound-Gaussian clutter.In:Proceedings of the 25th European Signal Processing Conference(EUSIPCO),2017
9 Ward K D,Tough R J A,Watts S.Sea clutter:scattering,the K-distribution and radar performance.Electron Lett,1981,17:561-563
10 Gerlach K.Spatially distributed target detection in non-Gaussian clutter.IEEE Trans Aerosp Electron Syst,1999,35:926-934
11 Billingsley J B.Exponential Decay in Windblown Radar Ground Clutter Doppler Spectra:Multifrequency Measurements and Model.Technical Report,1996
1)This paper focuses on the basic issue of detection of moving targets with a ground surveillance radar, taking into account ground clutter.
2)As known from standard probability, signal to noise after quadratic detection is equivalent to the square of the signal to noise at the input, for low SNR–whereas it is equivalent to the input SNR minus 3 dBfor high SNR.
3)Concerning the ratio r between the power of the stationary and diffuse components, it could be argued that wideband reduces the diffuse clutter more than the stationary clutter, since diffuse clutter is more evenly distributed. In other words,reducing the range cell always reduces the diffuse clutter by the same factor, whereas the stationary clutter is reduced by a lower factor(especially if it is spiky). Therefore, this comparison can be considered as a worst case scenario for wideband radar.
4)Actually, strictly speaking, for wideband radar, the longer integration time also decreases diffuse clutter with respect to the target RCS, in each Doppler cell. This does not change the CNR, since the noise is decreased similarly, but does decrease the clutter to target ratio. Therefore, this comparison can again be considered as a worst case scenario for wideband radar.
5)There may also exist rapid fluctuations of the target due to moving parts(jet engines, rotating blades, wheels);however, for moving targets detection, these parts have lower radar cross-sections than the cell of the target, so they can be ignored in this general assessment.
2 De Maio A,Greco S.Modern Radar Detection Theory.Raleigh:SciTech Pub,2016
3 Richards M A,Scheer J A,Holm W A,et al.Principles of Modern Radar.Raleigh:SciTech Pub,2010
4 Le Chevalier F.Wideband wide beam motion sensing.In:Advanced Ultrawideband Radar:Targets,Signals and Applications.Boca Raton:CRC Press,2016
5 Cherniakov M.Bistatic Radar:Principles and Practice.Hoboken:Wiley,2007
6 Chernyak V.Fundamentals of Multisite Radar Systems.Boca Raton:CRC Press,1998
7 Bidon S,Lasserre M,Le Chevalier F.Bayesian sparse estimation of radar targets in the compressed sensing framework.In:Compressive Sensing of Earth Observations.Boca Raton:CRC Press,2017
8 Petrov N,Le Chevalier F,Bogdanovic N,et al.Range migrating target detection in correlated compound-Gaussian clutter.In:Proceedings of the 25th European Signal Processing Conference(EUSIPCO),2017
9 Ward K D,Tough R J A,Watts S.Sea clutter:scattering,the K-distribution and radar performance.Electron Lett,1981,17:561-563
10 Gerlach K.Spatially distributed target detection in non-Gaussian clutter.IEEE Trans Aerosp Electron Syst,1999,35:926-934
11 Billingsley J B.Exponential Decay in Windblown Radar Ground Clutter Doppler Spectra:Multifrequency Measurements and Model.Technical Report,1996
1)This paper focuses on the basic issue of detection of moving targets with a ground surveillance radar, taking into account ground clutter.
2)As known from standard probability, signal to noise after quadratic detection is equivalent to the square of the signal to noise at the input, for low SNR–whereas it is equivalent to the input SNR minus 3 dBfor high SNR.
3)Concerning the ratio r between the power of the stationary and diffuse components, it could be argued that wideband reduces the diffuse clutter more than the stationary clutter, since diffuse clutter is more evenly distributed. In other words,reducing the range cell always reduces the diffuse clutter by the same factor, whereas the stationary clutter is reduced by a lower factor(especially if it is spiky). Therefore, this comparison can be considered as a worst case scenario for wideband radar.
4)Actually, strictly speaking, for wideband radar, the longer integration time also decreases diffuse clutter with respect to the target RCS, in each Doppler cell. This does not change the CNR, since the noise is decreased similarly, but does decrease the clutter to target ratio. Therefore, this comparison can again be considered as a worst case scenario for wideband radar.
5)There may also exist rapid fluctuations of the target due to moving parts(jet engines, rotating blades, wheels);however, for moving targets detection, these parts have lower radar cross-sections than the cell of the target, so they can be ignored in this general assessment.