Specifying the FDTD Boundary Conditions

The boundary conditions define 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.