Guilin Sun
Ansys Employee

When the incident angle is large, say 75 deg, BFAST may not provide enough benefits due to simulation time and accuracy.


Larger than 1 reflection usually means the simulation time is not long enough and (or) the autoshutoff min is not smaller enough. Please increase the simulation time 100 times longer and let the autoshutoff min to terminate the simulaiton. The default autofshutoff min is 1e-5 for most cases, but it can be reduced futher to 1e-6 or even smaller.

In addition, when the incident angle is large and there are higher diffraction orders, the diffraction angle can be very large or reach to 90deg, which makes PML performance degraded. Please also try to use Steep Angle PML with more PML layers.