Assigning Linked Impedance Boundaries

A linked Impedance boundary can be an isotropic or anisotropic impedance boundary in another design. Planar screens or grids of large extent with periodic geometry can be replaced by an Anisotropic impedance boundary. The boundary applies a homogeneous characteristic impedance to the surface in an effort to create an equivalent electrical representation of the geometric grid pattern. The link boundary can use an infinite ground plane and shell elements.

To assign a Linked Impedance boundary

1. Select a surface on which to assign the boundary and click HFSS>Boundaries>Assign>Linked Impedance to bring up the Linked Impedance Boundary dialog.
   
   
2. If you select Anisotropic Impedance, the dialog includes buttons to Setup X Direction Link, Setup Y Direction Link and a selection list for the Coordinate System.
   
   If the linked projects have wave ports, x and y directed projects are different and have to have one mode per port.
   If the linked projects have Floquet ports, x and y directed projects should be identical and have to have 2 modes per port (TE and TM modes). In that case, the field of mode 1 serves as x directed field, while the field of mode 2 serves as y directed field. It is also a valid setup to assign two different projects with Floquet ports, but with one mode per port.

3. The Coordinate System drop-down menu lists the Global Coordinate system and any relative coordinate systems if you have defined them in the design. Select the Coordinate System that defines the anisotropic characteristic of the impedance boundary. (See Creating a Relative Coordinate System.)
   Note:

   An anisotropic boundary must not touch ports in a design.

4. Select Infinite Ground Plane if you want the surface to represent an electrically large ground plane when the radiated fields are calculated during post processing.
5. Select Shell Elements if you want to the boundary modeled as a shell element.

With shell elements: Make sure two ports are defined, and for isotropic 1 mode on each port and for anisotropic 1 mode one each port when two designs are linked and 2 modes on each port when one design is linked.

Without shell elements: Allow either one or two ports but only 1 mode each for isotropic, 1 mode each for anisotropic with two linked designs, and 2 modes each for anisotropic with one linked design. An info or warning message is issued when two ports are defined in the design to let you know we only extract the link from one of the ports and specifies which one.