FDTD Boundary Conditions
From openEMS
Contents |
Usage
function FDTD = SetBoundaryCond(FDTD, BC, varargin)
BC = [xmin xmax ymin ymax zmin zmax];
Types of Boundary Conditions (BC)
- PEC: Perfect electric conductor (default BC)
- PMC: Perfect magnetic conductor
- MUR: A simple absorbing boundary condition (ABC)
- PML_x: Perfectly Matched Layer absorbing boundary condition, using x number of cells
openEMS example
BC = {'PEC' 'PMC' 'MUR' 'PML_8' 'PML_8' 'PML_10'}; FDTD = SetBoundaryCond( FDTD, BC );
Perfect electric conductor (PEC)
- All tangential electric fields on this boundary will be set to zero. This results in the behavior as a perfect electric conductor. This BC is the default in a FDTD simulation.
For example, this BC can be used to model waveguide walls or a infinite ground-plane for PCB board.
Perfect magnetic conductor (PMC)
- All tangential magnetic fields on this boundary will be set to zero.
- This results in the behavior as a perfect magnetic conductor. Since there is no real material with such a behavior, it is usually used as symmetry boundary condition.
- Since in FDTD all magnetic fields are shifted by half a cell, this wall is effectively located in the middle of the last two lines of the respective direction.
MUR ABC
- Simple absorbing boundary condition (ABC)
- Only works perfect for a completely orthogonal impinging waves with a known phase-velocity (e.g. speed of light)
PML_x ABC
- Artificial x-cells thick layer that effectively absorbs incoming EM waves. (default x=8)
- PML thickness can be 6 to 20 cells. PML_8 is a good default.
- Warning: In openEMS the last x lines in the respective direction are defined as this artificial absorbing material: Keep your structures far enough away!
- Info: This ABC is not optimally implemented regarding the simulation speed. Use the Mur-ABC for faster simulations.