CST2013: Settings for PML Boundary

Simulation: Settings Boundaries Open Boundary

This dialog box offers options to modify the parameters of the open boundary condition. Only experienced users should change these settings

The used PML formulation is the so called "Convolution PML" which provides a material independent absorbing boundary condition. In addition to electric and magnetic material properties also conducting materials are considered for this absorbing boundary.

Properties frame

Estimated reflection level: Specify the estimated reflection level (e.r.l.). Usually an e.r.l. = 1e-nPMLLayers = 1e-4 is sufficient.

Automatic minimum distance to structure frame

It is often useful, also for stability criteria, to enlarge the simulation domain so that the PML layer are not too close to the simulated structure. The available options in this frame determine the amount of this enlargement either as absolute fixed distance from the structure or in fixed relationship with the simulation wavelength.

Fraction of wavelength/Absolute distance combo box: this combo box allows to change the minimum distance criteria to be applied in case of open (add space) boundary.

The Absolute distance criterion describes a true distance enlargement. Type the amount in the adjacent edit box using geometrical user units.

The Fraction of wavelength determines the minimum distance to the open boundary in part of the wavelength following the formula Distance = Wavelength / Number. The reference frequency for the wavelength computation may be chosen in the At frequency field. In conjunction with the lines per wavelength setting within the Mesh Properties Dialog, this criterion might lead to a higher number of mesh lines between boundary and structure.

At frequency combo box: this combo box provides three possible choices. Center means that the reference frequency is the mid simulation frequency value, in formula FreqRef = (FMin+FMax)/2.

The second choice is Center and Monitors. In this case the reference frequency is the minimum non zero frequency selected among the center frequency and the user defined monitor frequencies. To this set belong the 2D and 3D field monitors and the far field monitors as well. This criteria is particular appropriate when the relevant monitors lie in the low simulation frequency range so that more appropriate settings for the PML are computed and better results are obtained.

The third possibility is User which enables to type directly the frequency in the adjacent edit box.

It should be noted that in any case 5 mesh cells will be considered as a lower limit to the domain enlargement. This default setting may be manually modified by VBA command Boundary.MinimumLinesDistance (double val).

OK

Accepts your settings and leaves the dialog box. You will return to the boundary dialog box.

Cancel

Closes this dialog box without performing any further action.

Help

Shows this help text.

See also

Frequency Range Settings, Mesh Properties

Boundary Conditions: Boundaries, Symmetry Planes, Phase Shift/Scan Angle, Unit Cell, Boundary Temperature