粗糙面散射对太赫兹雷达成像的影响
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摘要
传统毫米波安检雷达成像基于点目标假设而忽略了散射的影响,但随着频率提升至太赫兹(THz)频段,目标表面应视为粗糙而须考虑散射的影响。该文采用微扰法(SPM)求解粗糙表面的后向散射系数,在传统安检雷达成像模型的基础上模拟了不同粗糙度下的成像结果。通过与Lambert表面和理想镜反射表面的模拟成像结果对比,分析了粗糙度和频率等散射关键参数对太赫兹成像结果的影响。结果表明:在太赫兹安检雷达成像场景下,材料表面后向散射角越宽,成像质量越好;后向散射特性曲线的角宽度和形状共同影响成像分辨率和峰值旁瓣比;提高电磁波频率有利于粗糙表面成像。
Traditional millimeter wave security imaging radar ignores the effects of scattering due to the point target assumption.However,for frequencies in the terahertz band,the target surface should be modeled as a rough surface and the effects of scattering must be considered.In this paper,a small perturbation method(SPM)is used to get the backscattering coefficient of a rough surface.Then,the imaging results for the traditional security radar imaging model are simulated for various roughnesses.The effects of key scattering parameters including the roughness and frequency are then analyzed by comparisons with a Lambert surface and an ideal specular surface.The results show that a greater backscattering persistence angle improves the imaging quality with terahertz security radar imaging.The results also show that the angular width and shape of the backscattering characteristic curve both affect the imaging resolution and peak side lobe ratio.Finally,increasing the electromagnetic wave frequency facilitates rough surface imaging.
Traditional millimeter wave security imaging radar ignores the effects of scattering due to the point target assumption.However,for frequencies in the terahertz band,the target surface should be modeled as a rough surface and the effects of scattering must be considered.In this paper,a small perturbation method(SPM)is used to get the backscattering coefficient of a rough surface.Then,the imaging results for the traditional security radar imaging model are simulated for various roughnesses.The effects of key scattering parameters including the roughness and frequency are then analyzed by comparisons with a Lambert surface and an ideal specular surface.The results show that a greater backscattering persistence angle improves the imaging quality with terahertz security radar imaging.The results also show that the angular width and shape of the backscattering characteristic curve both affect the imaging resolution and peak side lobe ratio.Finally,increasing the electromagnetic wave frequency facilitates rough surface imaging.
引文
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[19]VARSHNEY K R,ETIN M,FISHER J W,et al.Sparse representation in structured dictionaries with application to synthetic aperture radar[J].IEEE Transactions on Signal Processing,2008,56(8):3548-3561.
[2]SHEEN D M,MCMAKIN D L,HALL T E.Three-dimensional millimeter-wave imaging for concealed weapon detection[J].IEEE Transactions on Microwave Theory and Techniques,2002,49(9):1581-1592.
[3]SHEEN D,MCMAKIN D,HALL T.Near-field three-dimensional radar imaging techniques and applications[J].Applied Optics,2010,49(19):E83-E93.
[4]SHEEN D M,FERNANDES J L,TEDESCHI J R,et al.Wide-bandwidth,wide-beamwidth,high-resolution,millimeterwave imaging for concealed weapon detection[C]//Proceedings of SPIE 8715,Passive and Active Millimeter-Wave Imaging XVI.Baltimore,USA:SPIE,2013:871509.
[5]COOPER K B,DENGLER R J,LLOMBART N,et al.THz imaging radar for standoff personnel screening[J].IEEE Transactions on Terahertz Science and Technology,2011,1(1):169-182.
[6]ALEXANDER N E,ALDERMAN B,ALLONA F,et al.TeraSCREEN:Multi-frequency multi-mode terahertz screening for border checks[C]//Proceedings of SPIE 9078,Passive and Active Millimeter-Wave Imaging XVII.Baltimore,USA:SPIE,2014:907802.
[7]GU S M,LI C,GAO X,et al.Terahertz aperture synthesized imaging with fan-beam scanning for personnel screening[J].IEEE Transactions on Microwave Theory and Techniques,2012,60(12):3877-3885.
[8]崔振茂,高敬坤,陆彬,等.340GHz稀疏MIMO阵列实时3-D成像系统[J].红外与毫米波学报,2017,36(1):102-106.CUI Z M,GAO J K,LU B,et al.Real time 3Dimaging system based on sparse MIMO array at 340GHz[J].Journal of Infrared and Millimeter Waves,2017,36(1):102-106.(in Chinese)
[9]XU F,WANG P.Analytical modeling of rough surface SAR images under small perturbation approximation[J].IEEE Transactions on Geoscience and Remote Sensing,2017,55(7):3694-3707.
[10]GROSSMAN E N,POPOVIC N,CHAMBERLIN R A,et al.Submillimeter wavelength scattering from random rough surfaces[J].IEEE Transactions on Terahertz Science and Technology,2017,7(5):546-562.
[11]DIGIOVANNI D A,GATESMAN A J,GOYETTE T M,et al.Surface and volumetric backscattering between 100 GHz and 1.6THz[C]//Proceedings of SPIE 9078,Passive and Active Millimeter-Wave Imaging XVII.Baltimore,USA:SPIE,2014:90780A.
[12]WEI J C,CHEN H,QIN X,et al.Surface and volumetric scattering by rough dielectric boundary at terahertz frequencies[J].IEEE Transactions on Antennas and Propagation,2017,65(6):3154-3161.
[13]JANSEN C,PRIEBE S,MOLLER C,et al.Diffuse scattering from rough surfaces in THz communication channels[J].IEEE Transactions on Terahertz Science and Technology,2011,1(2):462-472.
[14]SUNDBERG G,ZURK L M,SCHECKLMAN S,et al.Modeling rough-surface and granular scattering at terahertz frequencies using the finite-difference time-domain method[J].IEEE Transactions on Geoscience and Remote Sensing,2010,48(10):3709-3719.
[15]PTZOLD M,KAHL M,KLINKERT T,et al.Simulation and data-processing framework for hybrid synthetic aperture THz systems including THz-scattering[J].IEEE Transactions on Terahertz Science and Technology,2013,3(5):625-634.
[16]APPLEBY R,PETERSSON H,FERGUSON S.Concealed object stand-off real-time imaging for security:CONSORTIS[C]//Proceedings of SPIE 9462,Passive and Active Millimeter-Wave Imaging XVIII.Baltimore,USA:SPIE,2015:946204.
[17]ORTIZ-JIMNEZ G,GARCA-RIAL F,'UBEDA-MEDINA L A,et al.Simulation framework for a 3-D high-resolution imaging radar at 300GHz with a scattering model based on rendering techniques[J].IEEE Transactions on Terahertz Science and Technology,2017,7(4):404-414.
[18]郭立新,王蕊,吴振森.随机粗糙面散射的基本理论与方法[M].北京:科学出版社,2010.GUO L X,WANG R,WU Z S.Basic theory and method of random rough surface scattering[M].Beijing:Science Press,2010.(in Chinese)
[19]VARSHNEY K R,ETIN M,FISHER J W,et al.Sparse representation in structured dictionaries with application to synthetic aperture radar[J].IEEE Transactions on Signal Processing,2008,56(8):3548-3561.
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