如何建立复选框shield your waveguide ports

背面开槽之后仿真老是出错，
求解过程中出现The calculation seems to be unstable！A possible source of instabiliy could be given by inaccurate definition of internal waveguideports.Please consider to increase the dimension or shield your waveguide ports.
我百度了很久，只得到以下资料
CST MWS帮助文件《Waveguide Port》：
Electric shielding: Activate the check box to let the boundary of the waveguide port be treated as a perfectly shielding (PEC) frame.
CST MWS帮助文件《Special Solver Parameters - General》：
Electric shielding for all ports: A perfectly shielding (PEC) frame surrounding each waveguide port region will be added. This option causes higher reflections at ports. Therefore, it should only be used if a calculation has become unstable.
百度翻译：
电屏蔽：启动复选框让波导端口边界被视为一个完全屏蔽（PEC）框架。
电屏蔽所有的港口：一个完全屏蔽（PEC）框架周围每个波导端口区域将增加。此选项会导致更高的反射端口。因此，它应该只是如果计算已成为不稳定的使用。

当母语已无法表达清楚之时，请传上图档。

英语没学好，母语也不咋地……。
要么在waveguide port properties里设置：

要么在time domain solver里设置：