Reply To: Question about auto shutoff time

[Guilin Sun]

It does not diverge and autoshutoff is still 1 for so long simulation time might mean that you are using metal or periodic boundaries conditions without PML boundaries and with lossless materials.  While for periodic structure with plane wave excitation you will for sure use the periodic boundaries in the periodic directions, and PML along propagation, non-periodic structures usually use PML surrounding the structures. When the substrate is a metal, to aovid long simulation time, one may use perfect electronic metal to replace the real metal material but the other side of boundary should be PML.

Other causes of long simulation time might be due to many other factors, please refer to 

Ansys Insight: Slow convergence in FDTD

Please check your settings. If you still have the same issue, please post some screen copies here for the structure and settings. Otherwise please write a new post for any other questions.