HFSS中cover line的优化问题？

求教啊   各位大虾
最近在hfss中仿真了渐变线的定向耦合器，渐变线是由方程输入的曲线，再用cover line将两条曲线连接成面的，仿真没有问题，就是优化的时候老是报错。
Acis error: "Fail to cover lines. The given curve is open！ Make sure the curve is closed
" (8:12:50 上午  二月 02, 2012)
part1: CoverLine operation failed. (8:12:50 上午  二月 02, 2012)
Acis error: "Fail to cover lines. The given curve is open！ Make sure the curve is closed
" (8:12:50 上午  二月 02, 2012)
Acis error: "Fail to cover lines. The given curve is open！ Make sure the curve is closed
" (8:12:50 上午  二月 02, 2012)
求教各位大虾怎样解决这个问题  谢谢

请问小编的问题解决了吗?怎么解决的?

平面电路还是去IE3D中仿真和优化吧，效率更高