Changes

===Domain Boundary Conditions===

To solve an FDTD problem, proper boundary conditions must be enforced on the bounding walls of the solution domain. The current release of EM.Cube's [[FDTD Module]] supports four types of boundary conditions:

By default, all the six sides of the computational domain box are set to CPML, representing a completely open-boundary structure. Different boundary conditions can be assigned to each of the six sides of the domain box. The periodic boundary conditions are special ones that are assigned through [[FDTD Module]]'s Periodicity Dialog and will be discussed later under modeling of periodic structures. The current release of EM.Cube allows periodic boundary conditions only on the side walls of the computational domain, and not on the top or bottom walls.

The PEC and PMC boundary conditions are the most straightforward to set up and use. Assigning the PEC boundary to one of the bounding walls of the solution domain simply forces the tangential component of the electric field to vanish at all points along that wall. Similarly, assigning the PMC boundary to one of the bounding walls of the solution domain forces the tangential component of the magnetic field to vanish at all points along that wall. For planar structures with a conductor-backed substrate, you can use the PEC boundary condition to designate the bottom of the substrate (the -Z Domain Wall) as a PEC ground. For shielded waveguide structures, you can designate all the lateral walls as PEC. Similarly to model shielded cavity resonators, you designate all the six walls as PEC.

===A Closer Look At CPML===