武装直升机雷达散射截面计算及雷达吸波材料影响分析

为提高直升机雷达散射特性预估的准确性,建立了目标雷达散射特性分析的计算电磁学(Computational electromagnetics method,CEM)方法,并开展了吸波涂层对直升机雷达散射截面(Radar cross section,RCS)特性影响的研究。首先,对复杂目标(例如直升机)进行几何建模和网格划分,获得空间网格单元上的电磁场信息,作为整个电磁场仿真分析的计算基础。然后,通过介质球和涂覆电磁介质导体球的算例对比,分析结合共形技术的时域有限差分法(Finite difference time domain,FDTD)在处理介质物体及涂覆涂层介质物体的有效性,结果表明FDTD方法计算结果与级数解吻合。在此基础上,计算和对比了金属旋翼以及涂覆吸波涂层旋翼的RCS特性,分析了典型方位角入射下全机涂覆前后对RCS特性的影响。研究表明:旋翼表面全涂覆雷达吸波材料(Radar absorbing material,RAM)后对直升机旋翼的RCS抑制效果明显,在全机强散射部位涂覆RAM可以显著地降低RCS特性,涂层的使用在直升机的隐身设计中起到关键的作用。

Radar Cross Section Calculation on Armed Helicopter and Effect Analyses of Radar Absorbing Material

In order to improve the prediction accuracy of radar scattering characteristics of helicopters, the computational electromagnetics (CEM) method is established to analyze radar scattering characteristics, and the influence of coating on radar cross section (RCS) characteristics is studied. First of all, geometric model and mesh generation for complex target (such as helicopter) are conducted and the electromagnetic field information on the space grid unit is obtained for the simulation and analysis of the electromagnetic field. Secondly, the finite difference time domain (FDTD) method combined with conformal technique is effective in the treatment of dielectric objects and equivalent impedance method for dielectric coated objects through the calculations on the dielectric ball and the conductor ball coated with electromagnetic medium. The results show that the calculation results of the FDTD method agree well with the series solution. Then, the RCS characteristics of the metal rotor and the coated rotor are calculated and compared, and the influence of RCS on the characteristics of the fuselage before and after the coating is analyzed at different angles of incidence. It is demonstrated that the RCS reduction effect is obvious through the rotor surface coated with radar absorbing material (RAM). The whole body coating in the strong scattering parts can significantly reduce RCS and the use of coating plays a key role in the design of stealth helicopter.