Use the Scattering Boundary Condition to make a boundary transparent for a scattered wave. The boundary condition is also transparent for an incoming plane wave. The scattered (outgoing) wave types for which the boundary condition is perfectly transparent are
The field E0 is the incident plane wave that travels in the direction
k. The boundary condition is transparent for incoming (but not outgoing) plane waves with any angle of incidence. In addition, to an incident plane wave,
E0 can also be the electric field distribution for a Gaussian beam that propagates in the direction
k.
If there is an incident field, a Reference Point subnode can be added by right-clicking the context menu (right-click the parent node) or from the
Physics toolbar,
Attributes menu. The
Reference Point subnode redefines the incident field to be expressed as
where rref is a reference point determined as the average point from the point selection in the
Reference Point subnode.
Select an Incident field —
No incident field (the default),
Wave given by E field,
Wave given by H field, or
Gaussian beam. Enter the expressions for the components for the
Incident electric field E0,
Incident magnetic field H0, or
Gaussian beam electric field amplitude Eg0.
If Incident field is set to
Gaussian beam, edit the
Beam radius w0 (SI unit: m) and the
Distance to focal plane p0 (SI unit: m). The default values are
((10*2)*pi)/emw.k0 and
0 m, respectively. The optical axis for the Gaussian beam is defined by a line including a reference point on the feature selection with a direction specified by the
Incident wave direction (see below). By default, the reference point is the average position for the feature selection. However, by adding a
Reference Point subnode any available point (or the average of several selected points) on the feature selection can be used as the reference point. The focal plane for the Gaussian beam is located the
Distance to focal plane p0 from the reference point in the
Incident wave direction.
If the Incident field is not set to
No incident field, edit the
Incident wave direction kdir for the vector coordinates. The default direction is in the opposite direction to the boundary normal. For 2D axisymmetry, the
Incident wave direction kdir should be parallel or anti-parallel to the symmetry axis.
Select a Scattered wave type for which the boundary is absorbing —
Plane wave (the default),
Spherical wave, or
Cylindrical wave.
Select the Dispersion and absorption model that will be used when calculating the wave number and attenuation constant for the incident and scattered waves —
Low loss approximation (the default), or
High loss. For
High loss also enter a
Carrier frequency f0 (SI unit: Hz). The default is 1 GHz.