在微波频率下,雷达横截面(RCS)测量通常是通过将目标放置在天线的远场区域来执行的。来自天线的辐射场的波前可以近似为平面,确保入射场和功率独立于天线与目标相互作用。然而,对于电大目标,所需的距离变得很大,给实施带来挑战。缩放模型RCS测量提供了一种替代解决方案。在太赫兹和光学频率下的RCS测量通常需要准直光束作为源,其中截获的功率和RCS变得依赖于激励。为了解决这种依赖关系,研究人员建议修改RCS定义,以考虑截获的功率并分析性地表述散射问题。然而,这种修改需要事先了解目标的几何形状和材料属性,在实践中通常不容易获得。这也将研究限制在仅规范目标。在本文中,我们提出了一种模拟截获功率的替代方法。利用平面波谱理论将高斯光束分解为向不同方向传播的多个平面波。使用矩量的全波方法解决了散射问题。通过涉及球体和非规范目标的理论证明和数值示例,用一架缩放模型的飞机,我们证明了原始的RCS定义可以作为缩放测量的良好近似,前提是束腰大约是目标尺寸的四倍。这些发现为雷达工程师在使用准直光束进行缩放测量时提供了有价值的指导。结果,与从全模型测量中获得的匹配,使我们能够预测全尺寸目标的RCS。此功能有助于各种与目标相关的应用程序,如目标表征,分类,检测,甚至认可。
At microwave frequencies, radar cross-section (RCS) measurements are usually performed by placing the target in the far-field region of the antenna. The wavefront of the radiating field from the antenna can be approximated as planar, ensuring that the incident field and the power interact with the target independently of the antenna. However, for electrically large targets, the required distance becomes significant, posing challenges for implementation. Scaled-model RCS measurements offer an alternative solution. RCS measurements at terahertz and optical frequencies typically require a collimated beam as the source, where the intercepted power and RCS become dependent on the excitation. To address this dependency, researchers have proposed modifying the RCS definition to account for the intercepted power and to analytically formulate the scattering problem. However, such modifications require prior knowledge of the target\'s geometry and material properties, which are often not readily available in practice. This also limits the study to only canonical targets. In this paper, we propose an alternative approach for modelling the intercepted power. The Gaussian beam is decomposed into a number of plane waves travelling to different directions using the theory of plane wave spectrum. The scattering problem is solved using the full-wave method of moment. Through theoretical proofs and numerical examples involving spheres and a non-canonical target, with a scaled-model aircraft, we demonstrate that the original RCS definition can serve as a good approximation for scaled measurements, provided that the beam waist is approximately four times the target\'s dimensions. These findings provide valuable guidelines for radar engineers when performing scaled measurements using collimated beams. The results, which match those obtained from full-model measurements, enable us to predict the RCS of full-scale targets. This capability facilitates various target-related applications, such as target characterization, classification, detection, and even recognition.