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在飞机雷达截面（RCS）的理论预估中，飞机进气道的电磁散射计算是其难点之一。对于厘米波段雷达而言，进气道属于电大尺寸目标，而其终端一般还存在涡轮叶片之类的复杂结构，单用高频近似方法难以解决。本文介绍GRE－FDTD混合方法可用于进气道的电磁散射计算。该方法用广义射线展开法（GeneralizedRayExpansion，GRE）计算进气道前端的缓变部分，用时域有限差分法（FDTD）计算包括涡轮叶片的复杂结构段。计算结果与波导模式法（Modal）－炬量法（MoM）混合方法的结果相比较，二者有很好的一致性。
In the theoretical prediction of aircraft radar cross section (RCS), the calculation of the electromagnetic scattering at the air intake of an aircraft is one of the difficulties. For centimeter-band radars, the inlet port belongs to the target of electric large size, while the terminal generally has the complicated structure such as the turbine blade. The high-frequency approximation method alone is difficult to solve. This paper describes the GRE-FDTD hybrid method can be used for inlet electromagnetic scattering calculation. The method uses the generalized ray expansion (GRE) to calculate the slowly changing part of the inlet and calculates the complex structure section including the turbine blade by the finite-difference time-domain method (FDTD). The calculated results are in good agreement with those obtained by the Modal-MoM hybrid method.