加上介质为啥需要那么大的空间

我做的是1.7*4.5*1.4m的汽车模型（空心）RCS仿真，最先是不太懂，把它设成介电常数为3.5的介质，倒也出了个结果 ；
后来又把它加上窗玻璃，介电常数设为4，车体按理想导体，却出了一个错误
Required are   18.896 GByte for the file
"cartest2ke._20" in the directory "C:\Temp\"
However, there are only    9.405 GByte available.  吓我一大跳！
我又把它全部按理想导体算，又是很快就仿真完了，为什么会出现这样的问题?

你可以使用 V5.5 的版本... 他對汽車玻璃有做特殊的功能
https://www.feko.info/applications/antenna-design/windscreen-antennas
Problem DescriptionThe proliferation of communication devices that are required in modern automobiles, require automobile designers to include more and more antennas into their vehicle designs.  Requirements include FM/AM antennas, TV antennas, etc.  Aesthetically speaking, this is a problem that can only be overcome by including such antennas into vehicle designs in unobtrusive ways.  A prominent modern development is to include these antennas into the windscreens of a vehicle.  These windscreens include multiple layers of glass and wiring that form the antenna.  As with other antenna designs, engineers require the ability to simulate new designs to evaluate many antenna operating characteristics, including:
Efficiency
Impedance bandwidth
Far-field radiation characteristics
FEKO SolutionFEKO includes a solution method based on the MoM that can be used for rigorous analysis of windscreen antennas.  The method meshes only the metallic antenna elements, so the resource requirements that are devoted to modelling of the dielectric layers of the glass is almost negligible.  Features of the method include:
Boundaries of the dielectric interfaces between different layers of glass are accurately accounted for.
Coupling between closely spaced antenna elements are taken into account.
Finite size glass antennas can be integrated into a full car model.
Curvature and rotation of the window is considered.
Windscreen analysis example
On the right, a FEKO model of a car with integrated windscreen antenna is show. At the bottom, simulated and measured reflection coefficient data is compared. These results show that FEKO can predict the performance of such antennas very accurately.