We’re putting the final touches on our new badges platform. Badge issuance remains temporarily paused, but all completions are being recorded and will be fulfilled once the platform is live. Thank you for your patience.
Guilin Sun
Ansys Employee

请参考 

Ansys Insight: FDTD varFDTD 常见的发散原因以及处理  

 

我估计是有大角度衍射,你可能需要用Steep Angle PML,用更多层。