共查询到17条相似文献,搜索用时 156 毫秒
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该文提出一种基于柱面扫描近场成像的RCS(Radar Cross Section)测量新方法:以理想的各向同性点散射中心模型为核心假设,通过详细的理论推导给出了一种具有通用性的基于柱面扫描近场成像的RCS 测量方法。该方法先得到目标的3 维雷达散射图像,再通过这些等效理想散射中心的散射场叠加获得远处散射场进而给出目标的远场RCS 值。该方法不仅能得到被测目标的3 维雷达散射图像,还能获得一定立体角域的目标远场RCS。相比只能得到2 维雷达散射图以及2 维平面角域RCS 结果的圆迹扫描测试相比,该文所提的柱面扫描测试能得到更多的目标散射信息,具有较强的实用性。仿真结果验证了新方法的可靠性。 相似文献
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一种利用外推获得飞行器目标远场RCS方法研究 总被引:1,自引:0,他引:1
提出了一种球面波照射下获取室内飞行器目标RCS的方法。室内RCS测试难以满足远场条件,造成散射方向图畸变。针对飞行器目标机身高度较小,可将入射球面波等效为柱面波,然后借助参考目标,导出其在柱面波与平面波照射下的修正系数g(x)。再次,建立被测目标近距散射场与g(x)之间的关系,从而得到目标等效平面波照射下的远场RCS。仿真表明:与理论值相比,外推后的结果在有限角域内吻合良好。实验在微波暗室测量了飞行器目标在两个不同距离下的散射场,外推后RCS具有一致的收敛性,并与电磁计算结果进行比较,验证了外推技术具有较高的精度。另外,该方法对目标口径、纵深尺寸没有苛刻的限制。 相似文献
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微波3维成像能够准确地从背景噪声中分离出目标的散射信息,适用于外场目标电磁(EM)散射特性的分析和研究,因而从3维合成孔径雷达(SAR)成像的角度研究目标电磁的散射特性是目前的一个新兴的热门课题。该文以此为背景,首先从Stratton-Chu积分方程出发详细推导3维SAR的近场波数域成像过程,解释3维SAR成像的物理意义;然后阐述基于3维SAR成像的雷达散射截面积(RCS)近远场变换原理,介绍3维SAR图像的散射中心提取方法,给出基于3维SAR成像的RCS近远场变换算法;最后通过FEKO软件进行了仿真实验,得到了5个点目标的RCS近远场变换的方位特性曲线和频率特性曲线,并通过与理论情况的对比,验证该算法在RCS近远场变换技术中的有效性。 相似文献
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全尺寸目标的电磁散射特性测试,需要足够大的测试距离或紧缩场系统,但是建设满足远场条件的室外静态场与室内紧缩场需要巨大的经费投入和很高的技术条件,更无法对飞行器进行现场成像与雷达散射截面(Radar Cross Section,RCS)诊断.针对近距离测试检定飞行器隐身性能的需求,提出了基于散射分布函数模型的近远场变换算法.建立三维散射分布函数模型,采用三维扫描方式记录近场数据,将球面波函数分别在柱坐标系、三维直角坐标系与球坐标系下展开,变换得到目标的远场数据,通过三维逆傅里叶变换与插值算法给出目标的三维重建图像与远场RCS.仿真分析与实验表明,算法准确有效. 相似文献
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研究了三种针对一维线天线阵列的快速近场测量方法,仅需二维近场扫描数据即可外推出线阵的单切面远场方向图。这三种单切面远场方向图测量方法包括平面/柱面波波谱展开法、等效源求解法和多极子平面波展开法。针对单切面方向图测量中二维格林函数存在的幅度误差,提出了一种幅度误差补偿方法,显著降低了原始近场数据外推变换得到的远场方向图的幅度测量误差。通过矩量法仿真得到的一维低副瓣线天线阵近远场数据及其比较结果验证了所提出方法的有效性,并通过仿真算例对比分析了不同外推方法之间的优缺点。其中基于计算电磁学的等效源展开方法及多极子平面波展开方法因其具有显著减少的采样点数、不存在数据截断以及灵活的采样位置等优点,可广泛应用于多种一维线阵单切面方向图测试应用场景中。 相似文献
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Extrapolation of near-field RCS measurements to the far zone 总被引:5,自引:0,他引:5
An algorithmic procedure for extrapolating near-field radar cross-section (RCS) measurements to the far zone has been derived, coded, and experimentally validated. The deviation of the extrapolation algorithm uses an optical model to estimate the surface currents induced on the scattering body by the incident field, and a specially weighted version of the Fourier transform to calculate the near-field scattering amplitudes associated with such surface currents. The extrapolation entails three steps. First, near-field measurements of the scattered electric and/or magnetic field are used to infer the monostatic vector potential. Next, the inverse Fourier transform of the inferred vector potential is multiplied by a special weighting function to estimate an equivalent obliquity factor. Finally, the far-field scattering pattern is estimated by taking the Fourier transform of the reweighted obliquity factor. This extrapolation procedure has been validated using anechoic-chamber data taken on a right-circular aluminium cylinder 25 λ high and 2.5 λ in radius at near-field range of 19% of 2 D 2/λ where D is the nominal target diameter and λ the radiation wavelength. The extrapolated RCS pattern for this target was compared with an analytical estimate of its far-zone pattern and good amplitude and phase agreement was observed over a 20° cone of scattering angles 相似文献
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对近远场变换技术在目标特性测试中的应用进行了研究,通过对飞机模型的仿真结果进行近场成像处理、远场计算重构以及卷积积分修正等处理,可将近场散射变换到远场。同时,近远场变换技术能够有效解决在不满足远场条件下测量雷达散射截面积(RCS)时遇到的问题。通过对金属导体圆柱、导弹模型、常规飞机模型、角反射器等进行RCS测试,并对单柱面紧缩场与平面波紧缩场的RCS测试结果进行对比,得到近远场变换技术适用于那些采用隐身减缩技术的目标体,具有对测量数据进行一定程度的修正及提升测试精确度的效果。但对于未采取隐身措施的目标,近远场变换技术则完全不适用。 相似文献
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利用LOVE场等效原理.实现了从近场到远场的变换,很好地解决了应用时域有限差分法(FDTD)计算目标远场RCS(远场雷达散射截面)的问题,并应用Marlab编程成功实现了此算法.最后利用该方法求解了三个实例中的远场RCS问题.并将其计算结果与理论或其他计算方法所得的结果进行了比较.结果吻合较好. 相似文献
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Comparison and application of near-field ISAR imaging techniques for far-field Radar cross section determination 总被引:2,自引:0,他引:2
Inverse synthetic aperture radar (ISAR) imaging is a powerful tool for the characterization of scattering properties of radar targets. In particular, near-field techniques allow for short distance imaging with results comparable to those of standard far-field ISAR techniques. The resulting near-field images can be used to extract the far-field radar cross section (RCS) of the target overcoming the need for long-range measurement setups. This paper compares different near-field imaging techniques and reveals an in-depth insight into the imaging process, especially with regard to the subsequent RCS extraction. The performance of the different techniques together with processing improvements are demonstrated by means of numerical target models as well as by measured data of test objects and a scaled aircraft model. 相似文献
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Useful Analytical Formulae for Near-Field Monostatic Radar Cross Section Under the Physical Optics: Far-Field Criterion 总被引:1,自引:0,他引:1
《Antennas and Propagation, IEEE Transactions on》2009,57(1):205-214
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Overview of an image-based technique for predicting far-field radar cross section from near-field measurements 总被引:1,自引:0,他引:1
For the last 18 years, our group has been developing a variety of near-field-to-far-field transformations (NFFFTs) for predicting the far-field (FF) RCS of targets from monostatic near-field (NF) measurements. The most practical and mature of these is based on the reflectivity approximation, commonly used in ISAR imaging to model the target scattering. This image-based NFFFT is also the most computationally efficient because - despite its theoretical underpinnings - it does not explicitly require image formation as part of its implementation. This paper presents a formulation and implementation of the image-based NFFFT that is applicable to two-dimensional (2D) spherical and one-dimensional (1D) circular near-field measurement geometries, along with numerical and experimental examples of its performance. We show that the algorithm's far-field RCS pattern-prediction performance is quite good for a variety of frequencies, near-field measurement distances, and target geometries. In addition, we show that the predicted RCS statistics remain quite accurate under conditions where the predicted far-field patterns have significantly degraded due to multiple interactions and other effect. 相似文献
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Shyh-Kang Jeng 《Antennas and Propagation, IEEE Transactions on》1998,46(4):551-558
This paper proposes a method to compute the near-field RCS and Doppler spectrum of a target when the distances to the antennas are comparable to the target size. By dealing with a small piece of the target surface at a time, the transmitting antenna, and the receiving antenna are in the far-field zone of the small piece of the induced currents. The electromagnetic field produced by this small piece of induced currents can be written as a spherical wave. Sum up all spherical waves produced by every small piece of induced currents and we can obtain the total scattered field at the receiving antenna. The physical theory of diffraction (PTD) and the method of shooting and bouncing rays (SBR) are modified to evaluate the received signals. Numerical results based on these techniques are obtained and discussed. The formulation applies the simple concepts of “equivalent” image and vector effective height, which are believed to be novel 相似文献