Assigning Boundaries in HFSS
Boundary conditions specify the field behavior at the edges of the problem region and object interfaces. Within the context of HFSS, boundaries exist for two main purposes:
- to create either an open or a closed electromagnetic model or,
- to simplify the electromagnetic or geometric complexity of the electromagnetic model.
In an open problem, an air volume encompassing the outer radiating surfaces is modeled by a surrounding object. Radiation boundary conditions (ABC, PML or FEBI) are assigned to the outer radiating surfaces (i.e., faces of the region) to absorb all outgoing waves. HFSS users can choose one of the three workflows to analyze an "open" design.
- Auto-open region mode using the Solution type setting.
This workflow eliminates as much as possible the required interactions from a user and allows a designer to get to a robust solution quickly. It is intended for users who do not want to be aware of the region and the exterior radiation boundaries.
The open problem is enforced by the software automatically creates/maintains the region object and the ABC boundaries. HFSS applies the most appropriate out-of-the-box settings based on the geometries and the operating frequency. You do not need to (and cannot) edit these settings directly.
This mode restricts the design to a single solve setup. Users cannot manually create the region object, radiation boundaries or PML in this mode. Infinite ground plane, metallic IE region, primary/secondary (Lattice pair) and symmetry boundaries are also not allowed.
- Automation in setting up an open region problem using the Create Open Region command and Update Open Region Padding commands.
This workflow provides automations that assist a user to quickly setup an open problem. As a single user-customizable command, the software creates the region and the radiation boundaries based on user's selections on the region padding type, radiation boundary type, etc.
If necessary, you can further customize the design by editing these design objects directly.
- Advance mode
This is the original workflow where you manually set up the open design by assigning radiation boundary conditions.
You may assign the following types of boundaries to an HFSS design:
Represents a boundary condition used to replace a surface a planar screen or grid with periodic geometry. | |
| Aperture | Represents a hole in a metallic sheet assigned as an IE Region. |
Represents an imperfect conductor. | |
| Fresnel (SBR+) | Represents either a perfect absorbing boundary or a user-defined Fresnel table file that describes a good approximation of the reflection of an arbitrary wavefront off a surface. Supported for driven modal/terminal and SBR+ solution types. |
| Gradient Surface Roughness | Gradient Surface Roughness Boundaries address the situation where the conductors drawn in CAD models are perfectly smooth, but the manufactured surface is bumpy at microscopic scale. |
| Half Space | Represents a background comprising a dielectric half space. For antenna and scattering problems in HFSS in which all objects are assigned as Hybrid IE Region. |
Represents a resistive surface. | |
| Lattice Pair | A Coupled pair, the same as one Primary Boundary and one Secondary Boundary together, but with an auto-set coordinate system. A red arrow points from the primary to the secondary face of the Lattice Pair. |
Represents a structure with multiple layers as one impedance surface. | |
| Linked Impedance | Represents a data link to an isotropic or anisotropic impedance boundary in another design. These can include infinite ground planes and shell elements. |
Represents any combination of lumped resistor, inductor, and/or capacitor in parallel on a surface. | |
| Multipaction SEE | For Multipaction Analysis, this represents multipaction Secondary Electron Emission (SEE). The Multipaction SEE boundaries should be added to vacuum-material interfaces where secondary electrons will be generated. |
Represents a perfectly conducting surface. | |
Represents a surface on which the tangential component of the H-field is the same on both sides. | |
Represents an open boundary condition using several layers of specialized materials that absorb outgoing waves. | |
| Primary | Represents a surface on which the E-field at each point is matched to another surface (theSecondary boundary) to within a phase difference. |
Represents an open boundary by means of an absorbing boundary condition (ABC) that absorbs outgoing waves. | |
| Secondary | Represents a surface on which the E-field at each point has been forced to match the E-field of another surface (the Primary boundary) to within a phase difference. |
Represents a perfect E or perfect H plane of symmetry. |
You may also choose to designate a perfect E, finite conductivity, or impedance boundary as an infinite ground plane if you want the surface to represent an electrically large ground plane when the radiated fields are calculated during post processing.
Hiding boundaries also turns off a check for boundary overlaps during boundary assignment. In the case of very large models with many boundaries, hiding boundaries can prevent delays during boundary assignment. Full model validation will subsequently check for boundary overlaps.
For convenience, you can access the Edit Global Materials command from the Boundaries menu.
By default, the history tree in the 3D modeler window groups sheet objects according to boundary assignment. To change this, select the Sheets icon and right-click to display the Group Sheets by Assignment check box.