共查询到20条相似文献,搜索用时 31 毫秒
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High resolution imaging in the terahertz (THz) frequency range is investigated theoretically in this paper through the use of the high frequency methods in computational electromagnetics (CEM). Physical optics (PO), shooting and bouncing ray (SBR) and truncated-wedge incremental length diffraction coefficients (TW-ILDCs) methods are combined together to compute the scattered fields, which are then used to construct the inverse synthetic aperture radar (ISAR) images through two dimensional fast Fourier transform (2D-FFT). The corresponding ISAR images clearly show that high range and bearing resolution can be easily realized for THz carrier waves with broad bandwidth. 相似文献
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A shooting and bouncing ray (SBR) formulation is presented for treating the electromagnetic scattering from electrically large, inhomogeneous objects. A dense grid of rays representing the incident plane wave is shot toward the inhomogeneous objects. At the scatterer boundary, reflected rays and refracted rays are generated due to the discontinuity of the medium parameters. The trajectory, amplitude, phase and polarization of the rays inside the inhomogeneous object are traced based on geometrical optics. Whenever the rays cross the scatterer surface, additional reflected/refracted rays are generated and are tracked. This is repeated until the intensities of the refracted/reflected rays become negligible. The contributions of the existing rays to the total scattered field are calculated using the equivalence principle in conjunction with a ray-tube integration scheme. The ray formulation is applied to calculate the backscattering from cylinders and spheres and good agreement with the exact series solutions is observed in the high-frequency range. In addition, the backscattering mechanisms in penetrable objects are interpreted in terms of simple ray pictures 相似文献
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Shuen-Yih Wang Shyh-Kang Jeng 《Antennas and Propagation, IEEE Transactions on》1998,46(7):1112-1113
A compact closed-form formula for the RCS of a perfectly conducting right dihedral corner reflector at arbitrary aspect angles is presented. The approach is based on a combination of ray tracing, physical optics (PO), and the physical theory of diffraction (PTD). There is good agreement between the results obtained using the closed-form formula and those obtained by the shooting and bouncing rays (SBR) technique 相似文献
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Shuen-Yih Wang Shyh-Kang Jeng 《Electromagnetic Compatibility, IEEE Transactions on》1997,39(4):315-323
This paper presents a deterministic method to establish the scattering-center model for complex radar targets. By this method, high frequency techniques including physical optics, physical theory and diffraction and shooting and bouncing rays are used to establish scattering centers. Numerical results show that, by using this method with only single-frequency scattering centers at large aspect increments, the RCS pattern at finer aspect increments is well reconstructed; besides, it can be extended to predict the RCS pattern at any frequency of interest in a required narrow bandwidth. Good agreement between direct RCS calculation, scattering-center model and measured results is obtained 相似文献
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Bhalla R. Ling H. Moore J. Andersh D.J. Lee S.W. Hughes J. 《Antennas and Propagation Magazine, IEEE》1998,40(5):30-39
We present an automated technique to extract the three-dimensional scattering-center model of a target from its geometrical CAD model. The technique is based on the shooting and bouncing ray (SBR) method. In this article, we first review the basic concepts behind the three-dimensional scattering-center-extraction algorithm. Next, we present application examples of signature-data compression and radar-feature extraction, based on the scattering centers extracted from complex targets using such a methodology. We conclude by identifying some future areas of research 相似文献
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We present a high-frequency monostatic rcs, calculation code : Sermat which can be applied either to complex perfectly conducting or coated targets. This code operates on targets whose surface is described in terms of facets. It is an hybridization of the physical theory of diffraction for reflections and diffractions and the shooting and bouncing rays method for cavities. Written in standard Fortran, it can be run on Unix workstations. It is designed to fulfill industrial requirements (speed, precision...) and is extensively used by Matra Defense for its own needs. Some results are presented and compared with exact solutions and experimental data. 相似文献
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We present a technique to extract the three-dimensional (3-D) scattering center model of a complex target. Using the shooting and bouncing ray technique, we first generate the 3-D inverse synthetic aperture radar (ISAR) image of the target based on a one-look ISAR algorithm. In step two, we use the image processing algorithm CLEAN to extract the 3-D position and strength of the scattering centers from the 3-D ISAR image. Various implementation issues related to computation time and memory are addressed and an efficient scheme is presented to accomplish the 3-D scattering center extraction. Several examples ranging from simple canonical structures to complex targets are presented to demonstrate the validity of the extraction scheme and the usefulness of the resulting 3-D scattering center model 相似文献
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针对空空导弹无线电引信,用广义的雷达有效散射截面(CRCs)描述隐身目标近场散射特性.对覆盖吸波涂层的目标,以组合的三角形平面单元拟合目标的几何外形.利用物理光学法和物理绕射理论[1]计算目标每一单元的散射场和绕射场.考虑目标上的二次反射,计算无线电引信接收天线径上的目标电磁散射场.无线电吸波涂层目标的反射系数采用迭代方法计算,其方法可适用于具有任何类型电磁参数涂层的目标.以长空靶机和靶5目标为例,计算了其近场散射特性,为无线电引信设计提供参考依据.目标近场电磁散射特性的计算方法适用于隐身目标和非隐身目标. 相似文献
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Baldauf J. Lee S.-W. Lin L. Jeng S.-K. Scarborough S.M. Yu C.L. 《Antennas and Propagation, IEEE Transactions on》1991,39(9):1345-1351
A general method for calculating the radar cross section (RCS) from a three-dimensional target is described. The target is first constructed by using a solid-geometry-modeling computer-aided design (CAD) package. Following the shooting and bouncing ray (SBR) method, a very dense grid of rays is launched from the incident direction toward the target. Each ray is traced according to the geometrical optics theory including the effect of ray tube divergence, polarization, and material reflection coefficient. At the point where the ray exits the target, a physical optics-type integration is performed to obtain the scattered far fields. This method is tested using several simple examples involving interaction among plates, cylinders, and spheres. The theoretical results are generally in good agreement with measured data 相似文献
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微波方法到太赫兹散射特性建模的延拓面临两个关键的科学问题研究,其一是材料响应特性延拓,包括金属属性向合金属性过渡导致Drude模型无法准确描述,以及介质材料在太赫兹频段的响应模型研究;其二是表面随机粗糙结构、以及复杂细微精细结构在太赫兹频段下的散射行为建模方法的延拓研究。微波频段下可视同为光滑的金属表面在太赫兹频段可能呈现出表面微粗糙特性。此外,针对含介质涂覆或全介质表面太赫兹散射特性的建模,需要结合随机边界散射理论,建立多层描述模型,以涵盖其中的面散射和体散射现象。该文首先采用积分方程方法描述和分析了金属粗糙表面的太赫兹散射规律,与实测数据吻合较好。其次,对于含涂覆或介质材料的目标表面,除表面粗糙的影响外,材料内部的微小粒子成分(如碳粉、石墨、金属粉等)的电尺寸与太赫兹波长相比拟,实验显示其体散射贡献不可忽视。该文尝试用矢量辐射传输理论与积分方程方法结合的多层模型来描述含介质材料表面的散射特性,很好地解释了实测规律。最后,该文提出基于“半确定性”描述的射线追踪高频算法,实现了复杂目标表面相干和非相干散射特性的一体化快速建模,为超电大复杂目标太赫兹散射特性的建模分析提供有效手段。 相似文献
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对目标开展了二维RCS 成像仿真与实验研究,分别采用SBR 方法与解析方法计算目标的散射特性并
提取相应的二维RCS 成像信息,基于时域加窗技术对采样信号进行加权处理抑制旁瓣电平以提高成像质量,通过
Cross-Range 处理方法获取目标二维RCS 成像结果以表征目标散射的强弱分布,设计了斜置平板以及3 个小球这两
个典型案例,展开相应的二维RCS 成像仿真与实验分析研究。结果表明:二维RCS 成像仿真结果与测试结果吻合良
好,有效验证了二维RCS 成像仿真方法的有效性。 相似文献
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研究了自由空间复杂导体目标的太赫兹(THz)雷达散射截面(RCS)的高频求解方法。将并矢格林函数引入物理光学方法中,对自由空间环境进行考虑,推导出自由空间物理光学分析方法,并结合图形电磁计算(GRECO)方法,采用分区显示算法改进后,在Visual C++ 2010 程序中实现目标的OpenGL 显示,对自由空间复杂导体目标进行消隐判断,提取像素面元法矢量和深度缓存等有效信息,计算了自由空间复杂导体目标的THz RCS。最后,将程序计算结果与FEKO 软件仿真结果进行比较,结果证明该方法的有效性和准确性。该研究结果为THz 雷达未来在军事、天文和遥感等领域的应用提供了重要依据和方法。 相似文献