摘要
随着计算机技术的发展，我们可以借助AutoCAD软件用非线性有理B样条(NURBS)对目标进行精确的几何建模。然后结合OpenGL技术，从目标的图形显示中获取电磁计算所需的信息。图形电磁计算(Graphical Electromagnetic Computing，GRECO)方法就是在这样的环境下产生的，它具有诸如自动实现消隐，计算速度快，精度高等优点，目前被认为是求解高频区复杂目标的最有效的方法之一。
本论文做了以下研究工作：首先，实现了运用GRECO方法计算了高频区理想导体复杂目标的雷达散射截面(RCS)，分别应用了物理光学法(PO)和增量长度绕射系数法(ILDC)计算了目标的面元和棱边的电磁散射，最后综合面元与棱边的散射效应得到目标的总RCS。并应用了几个可视化加速的技巧，显著的提高了图形算法的计算速度。其次，改进了原先的棱边检测方法，使得棱边绕射场的计算精度大大提高。接着，进一步对涂覆雷达吸波材料的复杂目标进行了RCS计算。其中，涂覆目标面元的散射场是通过结合阻抗边界条件和几何光学法(GO)而得到；而涂覆目标棱边的散射场则是通过等效电磁流法求解阻抗劈的边缘绕射场近似得到的。最后成功地分析了目标在线极化模式下和圆极化模式下的电磁散射参量。
通过将大量计算结果与理论值或相关文献结果相比较，效果令人满意。实例证明了GRECO方法在高频区实时求解复杂目标的RCS的快速性和有效性。
With the development of the computer technology, Targets can be accurately modeled by NURBS in virtue of AutoCAD. In addition combining OpenGL technology, we can translate the source shape data of targets displayed on the computer screen to the data for RCS computing. "Graphical Electromagnetic Computing (GRECO)" was presented in these conditions, which has many merits such as detecting shadowed regions automatically, computing in real time and accurately and so on. At present GRECO is regarded as one of the most valuable methods of Radar Cross Section (RCS) computation in the high-frequency region.
Depending on these conditions, several researches have been completed in this paper: Firstly, Calculating RCS of complex conducting targets has been accomplished by GRECO method. The high-frequency RCS of targets are obtained through Physical Optics (PO) and Incremental Length Diffraction Coefficients (ILDC) respectively. At the same time some techniques for speeding up the computation are applied in this paper. Secondly, the precision of diffraction field of the edges of targets has been greatly advanced by improving the original method of detecting edges. The RCS of targets coated with Radar Absorbing Material (RAM) in the high-frequency region have been further computed. RCS of facets
of targets coated RAM was resolved by combining Impedance Boundary Condition (IBC) and Geometric Optics (GO) and RCS of those edges were approximated by computing the RCS of edges of impedance wedge through Method of Equivalent Currents. Finally, RCS of targets were analyzed under the linear polarization and circular polar mode.
Good argument has been found comparing the results calculated with this present approach with the theoretical ones and related literatures. The method adopted in this paper could analyze RCS of complex radar targets in the high-frequency region rapidly and efficiently in practical application.
引文
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