共查询到20条相似文献,搜索用时 125 毫秒
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建立了大尺度分层粗糙面散射物理模型, 基于Kirchhoff近似、几何光学和射线追踪方法, 推导给出粗糙面散射场的计算公式, 提出了一种快速模拟机载正下视合成孔径雷达(Synthetic Aperture Radar, SAR)探测冰川回波的数值仿真方法, 以帮助分析实测数据.对SAR系统设计、雷达回波信号处理算法研究都有很大帮助, 可以应用到星体地下结构探测回波的模拟.理论公式及数值仿真结果验证了此数值仿真方法的正确性.在不同的仿真场景和雷达系统参数下, 数值仿真模拟了冰川散射回波, 定量分析了冰层表面粗糙度、次表面粗糙度、山体倾斜度、雷达系统参数等对天底区域和非天底区域散射回波的影响.本文的仿真方法可以快速计算任意大尺度特定地形所对应的雷达探测仪回波数据. 相似文献
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该文给出了一种用层状介质中的混合势积分方程(MPIE)和基于RWG基函数的矩量法计算地下三维目标电磁散射的精确快速实施方法。对MPIE的RWG矩量法的开发、计算性能做了研究,尤其是对其中的多个不同形式的Sommerfeld积分的快速全波数值离散复镜像计算方法做了仔细研究。该文的实施方法退化到自由空间后的计算结果与解析解Mie Series吻合的很好,而且地下平板的计算结果也与以往公布结果吻合得很好,证实了该文实施方法的可行、高效、精确。除此以外,该文还计算了其它形状目标在不同大小、不同埋藏深度、以及不同地层媒质下的电磁散射特征。 相似文献
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Grandjean G. Paillou P. Dubois-Fernandez P. August-Bernex T. Baghdadi N.N. Achache J. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(6):1245-1258
The authors investigate the penetration capabilities of microwaves, particularly at L-band, for the mapping of subsurface heterogeneities such as lithology variations, moisture or sedimentary structures. The experiment site, the Pyla Dune, is a bare sandy area allowing high signal penetration and presenting large subsurface structures (paleosoils) at varying depths. Several radar data sets over this area are available. A polarimetric analysis of airborne synthetic aperture radar (SAR) data as web as the ground penetrating radar (GPR) sounding experiment show that subsurface scattering occurs at several places. The SAR penetration depth is estimated by inverting a scattering model for which the subsurface structure geometric and dielectric properties are determined by the GPR data analysis. These results suggest that airborne radar systems in a lower frequency range (P-band) should be able to detect subsurface moisture down to several meters, leading to innovative Earth observation systems for hydrogeology in arid regions 相似文献
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A correction of the conventional physical optics (PO) current close-to-perfectly conducting wedges based on an application of the uniform geometrical theory of diffraction (UTD) is presented. This improved PO current is used in a hybrid formulation in combination with the method of moments (MoM) to deal with three-dimensional scattering bodies of arbitrary shape. The accuracy of this hybrid method is demonstrated by some examples. As opposed to an application of the physical theory of diffraction (PTD), only surface current densities and no fictitious electric and magnetic line currents along the edges are involved which allows a uniform treatment of the MoM and the PO region by expressing the surface current density as a superposition of basis functions defined over triangular patches 相似文献
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The application of high-resolution space-borne Synthetic Aperture Radar (SAR) becomes more and more popular because of its all-weather and all-time data acquisition capability. However, the interpretation of SAR image can be rather difficult since there are tremendous differences between SAR images and optical images. SAR image simulation is helpful for interpreting SAR images. In this article, a practical approach of SAR image simulation is proposed for urban structures based on Incremental Length Diffraction Coefficients and Shooting and Bouncing Rays (SBR). SBR adopts both GO (Geometrical Optics) and PO (Physical Optics) to calculate the scattered field of targets. Models of buildings with slope roof and flat roof are simulated and inversed. Inversion results coincide well with models and verify the high precision of our approach. 相似文献
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Use of the Finite-Difference Time-Domain Method in Calculating EM Absorption in Human Tissues 总被引:1,自引:0,他引:1
Sullivan Dennis M. Borup David T. Gandhi Om P. 《IEEE transactions on bio-medical engineering》1987,(2):148-157
Although there are acceptable methods for calculating whole body electromagnetic absorption, no completely acceptable method for calculating the local specific absorption rate (SAR) at points within the body has been developed. Frequency domain methods, such as the method of moments (MoM) have achieved some success; however, MoM requires computer storage on the order of (3N) 2 and computation time on the order of (3N) 3 where N is the number of cells. The finite-difference time-domain (FDTD) method has been employed extensively in calculating the scattering of metallic objects, and recently is seeing some use in calculating the interaction of EM fields with complex, lossy dielectric bodies. Since the FDTD method has storage and time requirements proportional to N, it presents an attractive alternative to calculating SAR distribution in large bodies. This paper describes the FDTD method and evaluates it by comparing its results to analytic solutions in two and three dimensions. The utility of the FDTD method is demonstrated by a 3D scan of the human torso. The results obtained demonstrate that the FDTD method is capable of calculating internal SAR distribution with acceptable accuracy. With the availability of supercomputers, such as the CRAY II, the calculation of SAR distribution in a man model of 50 000 cells (1.27 cm per cell) appears to be feasible. 相似文献
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Denney B. S. De Figueiredo R. J. P. 《Multidimensional Systems and Signal Processing》2003,14(1-3):207-222
This paper introduces a method for predicting HRR radar signatures and SAR images by creating a parametric three-dimensional scattering model from existing measured or model-based HRR signatures and/or SAR images. The method identifies potential three-dimensional persistent scatterers and estimates their scattering patterns. The results are parametric HRR signature and SAR image reconstruction functions of range, azimuth, and elevation.The modeling is accomplished through a scattering-based tomography technique. This technique localizes potential scatterers by using a filtered back-projection algorithm for the inverse radon transform. Once found, potential scatterers may then have their two-dimensional (azimuth and elevation) scattering patterns parameterized through the use of a truncated spherical harmonic series.Results using the reconstructions from HRR data are presented. A M109 model is reconstructed based on HRR signatures. The model allows us to predict what the vehicle would look like from any arbitrary orientation using SAR. Finally an M548 vehicle is modeled using 26 measured HRR signatures. The model is shown to be better than the synthetic model data. Additionally we show that the new model results can be combined with the synthetic data to provide a better target model for signature matching. 相似文献
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提出了一种求解一维粗糙面与二维无限长临空目标复合电磁散射特性的新型混合算法。混合算法只需在粗糙面上进行一次积分运算,即可用基尔霍夫-亥姆霍兹方程(KH)描述电磁波经粗糙面后的散射情况,再用矩量法(MoM)分析目标的散射问题,通过KH与MoM的混合来体现粗糙面与目标之间的耦合作用。经与不同方法的对比,验证了混合方法的正确性,体现了混合方法较数值法在求解效率上的巨大优势。计算了粗糙面与临空目标的统计复合散射特性,分析了粗糙面的起伏参数、临空目标的形状以及粗糙面介质的电参数对复合散射特性的影响。 相似文献
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高分辨SAR目标散射中心模型分析 总被引:3,自引:1,他引:2
散射中心是光学区雷达目标电磁散射的基本特征,是高分辨SAR图像解译的根本特征。以高分辨SAR图像解译为应用背景,分析了目前典型的三种散射中心模型(理想点散射中心模型、衰减指数和模型、属性散射中心模型)的优缺.点和适用条件,并导出了模型及模型参数间的关系。通过理论分析、仿真及实测SAR图像数据验证了属性散射中心模型是目前最符合高分辨SAR图像解译应用需求的散射中心模型。在此基础上,分析了属性散射中心的特性与特点,为研究基于属性散射中心模型的高分辨SAR图像特征提取及解译方法奠定了基础。 相似文献
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针对机载多传感器成像战场态势感知的问题,提出了一种合成孔径雷达(Synthetic Aperture Radar,SAR)与可见光图像压缩感知融合增强方法。该方法首先对SAR与可见光图像分别进行压缩感知测量,得到压缩测量值,然后通过基于局部权值的融合方法实现对压缩测量值的融合,再利用有序度最优分割法提取SAR图像的强散射目标,最后对融合测量值重建得到初步融合图像,初步融合图像通过目标对比度增强得到最终融合图像。对多组图像进行了仿真分析,视觉及数值结果表明该方法能显著增强融合图像的目标对比度,提升了图像纹理清晰度,较大程度降低了图像融合过程中的数据计算量。 相似文献
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Runkle P. Nguyen L.H. McClellan J.H. Carin L. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(1):46-55
Radar scattering from an illuminated object is often highly dependent on the target-sensor orientation. In typical synthetic aperture radar (SAR) imagery, the information in the multi-aspect target signatures is diffused in the image-formation process. In an effort to exploit the aspect dependence of the target signature, the authors employ a sequence of directional filters to the SAR imagery, thereby generating a sequence of subaperture images that recover the directional dependence of the target scattering. The scattering statistics are then used to design a hidden Markov model (HMM), wherein the orientation-dependent scattering statistics are exploited explicitly. This approach fuses information embodied in the orientation-dependent target signature under the assumption that. Both the target identity and orientation are unknown. Performance is assessed by considering the detection of tactical targets concealed in foliage, using measured foliage-penetrating (FOPEN) SAR data 相似文献
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Jiangqi He Geng N. Nguyen L. Carin L. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(10):2182-2193
Three electromagnetic models are employed for the investigation of ultrawideband VHF scattering from tree trunks situated over flat and sloped terrain. Two of the models are numerical, each employing a frequency-domain integral-equation formulation solved via the method of moments (MoM). A body-of-revolution (BoR) Mote formulation is applied for a tree trunk on a flat terrain, implying that the BoR axis is perpendicular to the layers of an arbitrary layered-earth model. For the case of sloped terrain, the BoR model is inapplicable, and therefore the MoM solution is performed via general triangular-patch basis functions. Both MoM models are very accurate but are computationally expensive. Consequently, the authors also consider a third model, employing approximations based on the closed-form solution for scattering from an infinite dielectric cylinder in free space. The third model is highly efficient computationally and, despite the significant approximations, often yields accurate results relative to data computed via the reference MoM solutions. Data from the three models are considered, and several examples of application to remote sensing are addressed 相似文献
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Gilmore C. Jeffrey I. LoVetri J. 《Geoscience and Remote Sensing, IEEE Transactions on》2006,44(6):1454-1461
Two common Fourier imaging algorithms used in ground penetrating radar (GPR), synthetic aperture radar (SAR), and frequency-wavenumber (F-K) migration, are reviewed and compared from a theoretical perspective. The two algorithms, while arising from seemingly different physical models: a point-scatterer model for SAR and the exploding source model for F-K migration, result in similar imaging equations. Both algorithms are derived from an integral equation formulation of the inverse scalar wave problem, which allows a clear understanding of the approximations being made in each algorithm and allows a direct comparison. This derivation brings out the similarities of the two techniques which are hidden by the traditional formulations based on physical scattering models. The comparison shows that the approximations required to derive each technique from the integral equation formulation of the inverse problem are nearly identical, and hence the two imaging algorithms and physical models are making similar assumptions about the solution to the inverse problem, thus clarifying why the imaging equations are so similar. Sample images of landmine-like targets buried in sand are obtained from experimental GPR data using both algorithms. 相似文献
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Schulz-Stellenfleth J. Horstmann J. Lehner S. Rosenthal W. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(9):2017-2028
An across track interferometric synthetic aperture radar (InSAR) is used to image ocean waves. Across track InSAR data were acquired during the SAR INnterferometry Experiment for validation of ocean Wave imaging models (SINEWAVE) in the North Sea using an airborne X-band radar with horizontal polarization. A wind sea system was imaged at different flight levels and with different flight directions with respect to the ocean wave propagation direction. Simultaneously, ocean wave spectra were measured by a directional wave rider buoy. Thus, the experiment data comprises synthetic aperture radar (SAR) intensity, coherence, and phase images together with in situ measurements. As shown in a recent theoretical study by Schulz-Stellenfleth and Lehner (2001), across track InSAR provides distorted (bunched) digital elevation models (DEMs) of the sea surface. Using SINEWAVE data the DEM bunching mechanism is verified with in situ ocean wave measurements available for the first time. It is shown that significant waveheight as well as one-dimensional (1D) wavenumber spectra derived from bunched DEMs and buoy data are in good agreement for small nonlinearities. Peak wave directions and peak wavelength detected in bunched DEMs and SAR intensity images are compared with the buoy spectrum. Peak rotations of up to 30° with respect to the buoy spectrum are found depending on flight direction and flight level. Two-dimensional (2D) spectra of bunched DEMs, corresponding coherency maps, and SAR intensity images are intercompared. The signal-to-noise ratio (SNR) of bunched DEM spectra is shown to be about 5 to 10 dB higher than the SNR of SAR intensity image spectra 相似文献
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A superresolution signal processing algorithm is used for the identification of wavefronts from the fields scattered from several canonical targets. Particular wave objects that are examined are single and multiple edge diffraction, scattering from flat and curved surfaces, cone diffraction, and creeping waves. The scattering data are computed numerically via the method of moments (MoM) and are processed using a modified matrix-pencil algorithm. General properties of superresolution processing of such data-independent of the particular algorithm used-are assessed through an examination of the Cramer-Rao (C-R) bounds for basic scattering scenarios 相似文献