Changes

Figure 1: The boundary ABC cells placed outside the visible domain box.

EM.Cube provides Perfectly Matched Layers (PML) as absorbing boundary conditions. PML's are layers of fictitious complex anisotropic materials designed to absorb any incident electromagnetic wave at all angles of incidence. The advantage of using a PML boundary condition over other types of ABC is that you do not need to care about what material or combinations of materials exist at the boundaries, since the PML can absorb anything! The disadvantage of using PML is that they require more computational resources and more sophisticated update field equations. Several types of PML have been proposed in the FDTD literature. EM.Cube's [[FDTD Module]] uses the Convolutional Perfectly Matched Layer (CPML). This is based on a newer implementation of the complex frequency-shifted PML (CFS-PML) that uses recursive convolution. It has been shown that CPML is highly effective at absorbing evanescent waves and signals with a long time signature. Therefore, using CPML, you can place the boundaries much closer to the objects in the project workspace. <font color="red"><u>''' {{Note that |EM.Cube's default quarter wavelength offset for the domain box is a very conservative choice and can be reduced further in many cases. A offset equal to eight free-space grid cells beyond the largest bounding box usually give a more compact, but still valid, domain box.'''</u></font>}}

Figure 2: [[FDTD Module]]'s CPML Settings dialog.