Specifying the FDTD Boundary Conditions

The boundary conditions define the size and type of boundaries of the volume solved by the finite difference time domain (FDTD) solver.

1. On the Solve/Run tab, in the Solution Settings group, click the  FDTD Boundary Conditions icon.

   
   

   

   
   Figure 1. The Boundary Condition Settings dialog (Top (+Z) tab).

2. On the Boundary Condition Settings dialog, click the Top (+Z) tab to specify the boundary in the positive Z axis.
3. Specify the boundary definition by selecting one of the following from the Boundary definition drop-down list:
   • To specify an open radiating boundary, implemented as a convolutional perfectly matched layer (CPML), select Open.
   • To specify a PEC boundary that allows efficient simulation of infinitely large electrically conducting planes, select PEC.
   • To specify a PMC boundary that allows efficient simulation of infinitely large magnetically conducting planes, select PMC.
4. Enlarge a volume by adding a free space buffer¹ by selecting one of the following:
   • If no free space buffer is required, select Do not add a free space buffer.
   • To automatically add a free space buffer (perpendicular to the specific face), select Automatically add a free space buffer.
   • To specify the size of the free space buffer to be added to the specified face, select Specify the size of the free space buffer.
     • In the Free space buffer region size field, enter a value.
   • To specify the position of the free space buffer on the respective axis, select Specify the position of the free space buffer boundary.
     • In the Position on the Z axis field, enter a value.
5. Repeat Step 2 to Step 4 for the remaining five faces of the boundary.
6. Click OK to define the boundary condition and to close the dialog.
   Note: A free space boundary condition is only displayed in the 3D view when the Configuration tab is selected.

   
   

   

   
   Figure 2. An example of the display for six free space boundary conditions.