请教电大金属介质混合目标的RCS计算问题？

请问下，我在用feko计算一个目标的RCS时，用PO算是总是报错，说什么什么不能同时计算；用GO算是更是不行！
    不知想计算一个混合金属和介质的目标RCS时，应该怎样设置?怎样才能仿真呢?
                    请教高手的指点。不胜感激！

咋没得人回答我呢。

1. 参考 3 RCS of a thin dielectric sheet
Keywords: RCS, thin dielectric sheet (TDS), plane wave
The electrically thin dielectric plate, modelled with the thin dielectric sheet approximation, is illuminated by an incident plane wave such that the bistatic radar cross section may be calculated at 100 MHz.
2. 参考 16 Dipole in front of a plate modelled using UTD, GO and then PO
Keywords: UTD, PO, GO, dipole, radiation pattern, far field, electrically large plate
A dipole in front of an electrically large square plate is considered. This simple example illustrates the differences in required meshing between UTD, GO and PO. The results from all three these methods are compared to the full MoM solution. First the dipole and the plate is solved with the MoM. The plate is then modified so that it can be solved with UTD, GO and later PO. The MoM/UTD, MoM/GO and MoM/PO hybrid solutions demonstrated here are faster and require less resources than the full MoM solution. These approximation can be used to greatly reduce the required solution time and resources required when they are applicable.
3.  http://www.feko.info/overview-of-feko
Numerical methods
The FEKO solver is based on the Method of Moments (MoM) and was the first commercial code to utilise the multi-level fast multipole method (MLFMM) for the solution of electrically large problems when it was released with Suite 4.2 in June 2004. In FEKO, the MoM is hybridised with the following solution techniques:Finite Element Method (FEM)
Physical Optics (PO)
Geometric Optics (GO) based on ray launching
Uniform Theory of Diffraction (UTD)
This hybridisation implies that these solution techniques can be applied to different parts of the same model to optimise the solution time and results.
4. SOLUTION TECHNIQUES
． Method of Moments (MoM)
． Multi-level Fast Multipole Method (MLFMM)
． Finite Element Method (FEM)
． Physical Optics (PO)
． Ray-Launching Geometrical Optics (GO)
． Uniform Theory of Diffraction (UTD)
． Planar and Periodic Green Functions
． True Hybridisation of MoM/FEM, MoM/PO,MoM/GO and MoM/UTD
． MoM for Multiple, Complex Dielectric Bodies

遇到了类似的问题，看了webhugo 推荐的几个例子，但是没有发现问题究竟在哪，开始用mom仿了一个简单的喇叭天线，后来又加上了一个金属平板，平板想用UTD，就报了错误，说是“error 33479：waveguide ports and UTD/diel .GO are not allowed simultaneously