共查询到19条相似文献,搜索用时 171 毫秒
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目标识别是雷达探测领域研究的难点问题,本文利用无载频脉冲探地雷达系统对有耗媒质中细长导线状和环状金属目标的瞬态散射特性进行了实验测量,并利用极点展开理论对谐振现象的产生给予了分析和讨论。在瞬态脉冲激励下,有耗媒质中的目标能够产生外部振荡现象,目标谐振时雷达接收信号的幅值比非谐振时大得多。谐振信号的产生与目标形状和特性、媒质参数、激励脉冲的宽度和天线极化特性等因素有关。 相似文献
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探地雷达最优工作信号与脉冲波形畸变的整形技术 总被引:1,自引:0,他引:1
利用信号检测理论,在雷达接收天线端信号的信噪比最大时,推出浅层地下目标探测雷达的工作信号形式是基带脉冲。该脉冲波是媒质参数、目标特性和目标埋深的函数。脉冲波在有耗媒质中传播时,既要引起幅度的衰减又要产生波形失真。通过分析波形失真的原因,提出了一种对失真波形进行整形的方法。 相似文献
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FD—TD法计算色散媒质中埋入异常体的电磁散射 总被引:5,自引:3,他引:2
本文论述了FD-TD法用于计算地下浅层目标的电磁散射问题。推出了Debye型色散媒质中FD-TD法的迭代公式和吸收边界条件。通过将FD-TD法计算的结果与其它结果相比较,证实了该方法计算有耗媒质中电磁场问题的有效性。对瞬态脉冲在色散媒质中的传播特性进行了讨论。分别计算了典型地下目标的散射波形和波形堆积图。 相似文献
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由于电磁波在穿越不同介质时会出现折射现象,因此在对地下目标成像时,电磁波信号在穿越从雷达到达地下目标的组合通道时,路径不是直线而是折线,此时利用常规的自由空间中的合成孔径成像方法已经不能对目标进行成像。为此,基于电磁波的传播规律和地层有耗媒质的特性,提出了电磁波传输的半空间模型,使其能够充分反映电磁波信号在整个传播过程中的真实路径,并得到了相应的目标回波表达式。将其应用到机载条件下的地下目标成像之后,通过仿真比较,可以明显看出,使用半空间模型对地下目标成像效果有改善,验证了半空间模型适用于对分层土壤中的地下目标成像。 相似文献
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瞬变电磁波在色散媒质中的传播与散射 总被引:2,自引:0,他引:2
色散媒质中瞬变电磁波的传播与散射等问题的计算分析是比较困难的,特别是在时域直接分析更加困难,本文采用时域的有限差分析来分析色散媒质中的瞬变场能直观可靠地反映其特性,为色散媒质中瞬变场的分析与研究和对目标识别,电磁兼容和隐形技术等领域的理论及应用研究提供了一种简便有效的数值计算方法。 相似文献
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A method-of-moments (MoM) analysis is applied to the problem of determining late-time resonances of dielectric bodies of revolution buried in a lossy layered medium, with application to plastic-land-mine identification. To make such an analysis tractable, we have employed the method of complex images to evaluate the layered-medium Green's function. The application of this method to resonant structures characterized by complex resonant frequencies, introduces numerical issues not manifested at real frequencies (i.e., for driven problems) with such discussed here in detail. Numerical results are presented for several buried targets in which we demonstrate, for example, the spiraling character of the resonant frequencies of particular targets as a function of the target depth 相似文献
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A frequency-domain method-of-moments (MoM) algorithm is used to model short-pulse plane-wave scattering from a wire buried inside a lossy, dispersive half-space with the time-domain scattered fields computed via the Fourier transform. Further, the complex resonant frequencies of such targets are also calculated via the MoM. The phenomenology associated with scattering from a buried wire is investigated in detail, and it is demonstrated that the time-domain scattered fields and the target resonances depend on the buried-wire orientation as well as the electrical properties of the half-space 相似文献
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In the scattering process of electromagnetic waves from dielectric or conducting targets, one often encounters resonances in frequency in the returned echo signals. In previous studies on the scattering of acoustic and elastic waves, analogous resonant echoes were shown to contain a wealth of information on the properties of the scattering target, permitting, in fact, the complete solution of the corresponding inverse problem. The same is recognized to be the case for the electromagnetic scattering problem considered here. For the case of dielectric or coated conducting spherical targets, the spacing and the widths of the resonances are shown to determine the dielectric constant and the coating thickness of the target in a direct fashion. 相似文献
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基于两层均匀媒质的GPEN SAR地下目标成像方法及其性能分析 总被引:3,自引:0,他引:3
地表穿透合成孔径雷达(Ground PENetration SAR,GPEN SAR)为了探测掩埋在地下的目标,通常工作在多层媒质的环境中。传统成像模型是建立在同一均匀媒质的假设上,不再适合于GPEN SAR的实际情况。本文首先建立了两层分区均匀媒质中的成像模型,然后利用后向投影(BP)算法定量分析了成像几何参数、土壤参数等对成像的影响,进而提出了一种修正的后向投影(MBP)算法。MBP算法不仅能够校正两层分区均匀媒质对成像定位的影响,还能估计目标的掩埋深度,提供目标三维位置坐标。仿真结果验证了MBP算法在不同信噪比环境下,对多目标的三维定位精度能满足实际的需要。 相似文献
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设计了一种中心对称的分裂环形状超表面结构,该结构具有偏振不敏感和高品质因子的特性。通过理论和实验研究,深入分析了其谐振点的频谱特性,并确定了谐振峰的模式,包括LC、偶极和高阶谐振等。其中,几种高阶谐振模式表现出较高的高品质因数Q(约230),并且对超表面衬底材料的介电常数变化高度敏感。此外,还研究了具有不对称超表面结构的电磁性质,发现通过分别增加超表面结构沿水平轴(x轴)和垂直轴(y轴)的不对称性,可以产生和增强0.332 THz和0.210 THz的谐振。 相似文献
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为研究一维分层介质粗糙面之间金属目标的复合电磁散射特性,该文提出了一种结合前后向迭代算法(FBM)和双共轭梯度法(Bi-CG)的快速互耦迭代算法(CCIA)。推导了分层粗糙面与金属目标的耦合边界积分方程组,采用FBM和Bi-CG分别求解分层粗糙面与目标的边界积分方程,目标和分层粗糙面的相互作用通过更新两方程的激励项来实现。计算了双层介质高斯粗糙面及无限长金属圆柱的复合电磁散射特性,当目标尺寸趋于零时与只有分层粗糙面的散射系数相吻合,验证了该算法的正确性;分析了不同粗糙面情况下该算法的收敛性;讨论了目标尺寸与位置变化对复合散射系数的影响。结果表明,金属目标的存在明显影响了分层粗糙面的散射特性。 相似文献
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Rieger W. Haas M. Huber C. Lehner G. Rucker W.M. 《Antennas and Propagation Magazine, IEEE》1999,41(2):33-36
The two-dimensional inverse electromagnetic-scattering problem of reconstructing the material properties of inhomogeneous lossy dielectric cylindrical objects is considered. The material properties are reconstructed from measured far-field scattering data, provided by the USAF Rome Laboratory Electromagnetic Measurement Facility in Ipswich. The targets in the Ipswich data set include perfectly electrically conducting (PEC) targets, penetrable (PEN) targets, and hybrid targets. A new method, which incorporates a priori information about the material properties, is proposed to solve the nonlinear inverse-scattering problem 相似文献
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Clutter suppression method in GPR using particle clustering 总被引:1,自引:0,他引:1
In this paper, a novel clutter suppression method in Ground Penetrating Radar (GPR) is proposed. Time segments of hill are represented by their corresponding particle in B-scan. Those particles in B-scan are clustered to represent reflectors (such as buried targets, air-soil interface). The clusters of buried target have a particle sequence with single peak. Therefore, if the particles donot belong to the cluster of buried target, time segment they represent will be suppressed. Experimental results and simulation are provided to demonstrate that the new algorithm outperforms existing ap-proaches. 相似文献
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Heyman E. Friedlander G. Felsen L.B. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1989,77(5):780-787
Complex resonances furnish valuable inputs for classification of radar signatures from irregularly shaped objects. An important class of targets involves open-ended enclosures with exterior-interior coupling. If the interior has waveguide-like properties, modal expansions can model the wave phenomena there, while ray methods can be employed to account for multiple diffraction at the aperture edges, and for wave interactions around the exterior boundary. By self-consistent ray-mode coupling in a hybrid format, one can construct a global resonance equation whose solutions yield the complex resonant frequencies for the composite object. The importance of evanescent modes and of coupling to nearest neighbor modes is investigated, as is the contribution from low-Q interactions around the external circumference 相似文献