4-1 Section 5: Materials Module Getting Started: Ansoft HFSS 8.0

4-2 Synopsis ò The Material Setup Module ò General Overview ò Assigning Materials n Solution Options: Surface or Inside ò Creating Materials n Standard n “Functional” n Anisotropic and Ferrites n Anisotropic Alignment ò Material Setup Exercise: Microstrip to Coax Transition Model ò Creating Materials, Assigning Materials, and Altering Solution Options

4-3 The HFSS Material Setup Interface Selection Options Single, Multi, by name, All Object Listing Only 3D Solids will be listed!! Material assignment. and solution options shown Material List Shows current material database; includes buttons for assigning matls. to objects and creating/editing new materials. Exit Button Exits Matl. Setup and asks if changes should be saved. Matl. Attributes Shows name and type of current material Mat’l. Characteristics Shows parameters for current material Graphical View Window Shows geometry, permits point-and-click selection and assignment. Graphical View Controls

4-4 Assigning Materials to Objects n Select the Object(s) n Graphically, by clicking n From list, by clicking n With Multiple Select enabled, may select more than one object and assign material to all simultaneously n Select the Material to apply from the list n Note: Capitalized material names are sorted above lower- case material names n Only a single material may be selected at a time, regardless of mode n Click the “Assign” button n Object list will update to show material assignment Result Shown in List

4-5 Solution Options: Surface or Inside? n “Slvin” Column indicates whether HFSS will perform the FEM solution in the interior of the object, or only on its surface n Meshing of volume will be performed regardless; but if ‘No’ is indicated, tetrahedra vertices interior to the object will not be used as unknowns in matrix construction n When assigning materials, object will default to assumption of interior solution selection n High Conductivity materials will assume “No” n Low or No Conductivity materials will assume “Yes” n Change by selecting object, and clicking appropriate “Solve...” button LIMITATIONS: Interior solution is required for perfect insulators (conductivity = zero). Interior solution is forbidden for perfect conductor (conductivity = infinite). In most cases, the auto- selection will be correct; interior solution for metals is only necessary when object size is on same order as skin depth. We do want solution inside dielectric......but don’t need it inside center conductor.

4-6 New Material Creation n The Material button provides drop-down options for material creation n Add will create a new listing n Derive creates a new listing based on the currently selected material n Clear removes a material from the list, and Underive removes a derivation association n Enter the Name for the new Material in the Attributes box, and select type n Enter appropriate Material Parameters in the Characteristics box n After parameter entry is complete, click “Enter” NOTE: Materials created in a project will appear in the listing for that project only, and will be defined as “Local” rather than “External (lock)”. To edit, add, or delete a material from the “External (lock)” listing, use the Material Manager from the Maxwell Utilities Toolbar. 4.

4-7 “Functional” Material Creation n Material Parameters may also be functions which can be altered for design or sensitivity studies. n Under “Options” button, define parameters to be functions rather than constants n Under “Functions” button, define functions and initial values n In Characteristics Box, enter name of function assigned to functional characteristic n Material function value can now be altered by macro control or Optimetrics TM package

4-8 Special Material Types n HFSS can also assign anisotropic and nonlinear (ferrite) material parameters n Type selected in Attributes box sets layout and entry options in Characteristics box n Anisotropic material characteristics are assigned for the ‘diagonal’ terms across the tensor matrix n Material can be oriented so that diag[1] need not be X axis, etc. n Ferrite setup requests material parameters assuming ferrite is biased above saturation. Anisotropic Material Parameter Setup Ferrite Material Parameter Setup

4-9 Anisotropic Material Alignment n When an Anisotropic Material is Assigned to an object, the window at left automatically requests alignment of the anisotropic properties to the geometry n “with object’s orientation” aligns the tensors diag[1], diag[2], and diag[3] to the object’s X, Y, and Z axes, respectively n “relative to object’s orientation” allows entry of relative rotation angles from the object’s X, Y, and Z axes along which to define the diag[1] - [3] tensors, respectively n “with a given direction” allows entry of relative rotation angles from the global X, Y, and Z axes (for the entire geometry, not just the object selected) along which to define the diag[1] - [3] tensors, respectively. n The Function checkbox allows definition of a variable in the About X, About Y, or About Z fields, which can then be altered by the Optimetrics TM package.

4-10 Material Setup Lab: Coax to Microstrip Model n We will now proceed through a Lab Exercise, Assigning all Materials for a pre-constructed geometry n The model is a Coax to Microstrip line transition, constructed to assume that the coax begins as a cable or connector (with Teflon dielectric), then penetrates a thick metal wall as an air dielectric line, before connecting to the microstrip trace n The lab will demonstrate assignment of existing materials to volumes, altering solution options, and creating a new material

4-11 Material Exercise: Open Material Setup 1. Find the project named “mat_exer” in the Project Manager, and Open it. Only the ‘Draw’ portion of the HFSS Executive Window design checklist should be checkmarked. 2. Select “Setup Materials...” to access the Material Setup module of HFSS. 3. Familiarize yourself with the objects in the model by clicking on their names in the Object list, one at a time: The ‘air_volume’ is a box solid, containing the entire microstrip circuit volume (substrate included) and the coax transition region. ‘substrate’ is another rectangular solid, resting in the bottom portion of the ‘air_volume’ solid. The ‘coax_outer’ is a cylinder, representing the dielectric inside the coax connector. The ‘pin’, ‘pin1’, and ‘pin2’ objects represent different lengths of the coaxial center conductor and transition. The ‘thru_hole_in_wall’ cylinder represents the air interior to a hole drilled in the wall of a metal enclosure (the rest of which did not need to be modeled as geometry). NOTE that there is NO listing for the ‘trace’ object, which is a 2D surface, or the ‘port’ outline, although both objects are visible in the graphical window!

4-12 Material Exercise: Assign Air and Teflon Volumes 1. From the graphical window or the object list, select the volume objects “air_volume” and “thru_hole_in_wall”. (Multiple select mode must be enabled to select more than one object.) 2. In the Material listing, scroll until you see the entry for ‘air’ and highlight it with a mouse-click. As the material is selected, its attributes and parameters will appear in the window beneath the graphical view. 3. Just above the Material listing, click the Assign button. This assigns the material ‘air’ to the selected volumes. Their entries in the object list will be updated to reflect the material assignment, and the ‘Slvin’ column will update to read “Yes”. 4. Select the volume object “coax_outer” from the list or graphical window. 5. In the Materials list, locate and select “Teflon” (remember, capital-name materials are sorted above lower-case-name materials). 6. Click the Assign button to assign the “coax_outer” volume to Teflon. The entry in the list will be updated to reflect the assignment, and to show “Yes” in the ‘Slvin’ column

4-13 Material Exercise: Assign Metal Volumes 1. From the graphical window or the object listing, select the objects “pin”, “pin1”, and “pin2”. 2. In the Materials list, find and highlight “copper”. 3. Click the Assign button. Note that the entries for the three “pin” objects are updated to reflect the material assignment, but in their case the ‘Slvin’ column indicates “No”. It is assumed -- due to the high conductivity of copper -- that no field solution is desired interior to these volumes. Instead, the surfaces of these objects will be covered with an appropriate impedance boundary to represent the conductivity and permeability effects of the material assignment at the frequency to be analyzed. 4. Let’s pretend we want to override this assumption for the “pin1” object, which is the half-cylinder providing the connection to the microstrip trace. In the Object list, select “pin1”. 5. Just above the Material listing, press the button labeled “Solve Inside”. The interface will provide a warning message, indicating that ‘solving inside a good conductor may require a large mesh’. Dismiss this message by pressing the “OK” button and note that the ‘Slvin’ column for the “pin1” object now reads “Yes”

4-14 Material Exercise: Create New Substrate Mat’l and Assign 1. Just above the Materials list is a drop-down menu labeled Material. Click on this and select Add from the listing. A new material entry will appear in the list entitled “Material80” (your number may differ slightly). Note that the Attributes box also shows this name, and that the characteristics listed show values resembling vacuum. 2. In the Attributes box, change the material name to “alumina_pure”. Leave the check boxes beneath the name field as they are (unselected). 3. In the Characteristics box, enter the following material parameters: Rel. Permittivity: 9.6 Rel. Permeability: 1.0 Elec. Loss Tan: Mag. Loss Tan: 0 4. In the Attributes box, press the Enter button. This completes creation of the new material, but does not assign it to any geometry. 5. In the Object listing, select the “substrate” object. 6. Select “alumina_pure” from the Material listing if it is not still selected. 7. Press the Assign button to assign the newly created material to the “substrate” object. Since all objects now have material conditions assigned, we can press the Exit button at the lower left, and confirm that we do want to save our changes. We have now completed the Material Setup Exercise (not shown)

4-15 The Material Manager n Off the Utilities Toolbar in the Maxwell program, the Material Manager allows access to the ‘permanent’ material database used by HFSS n Every material shown as “External(Lock)” by the HFSS Material Setup module is “Local” to this interface n The Material Manager is a ‘common’ product between HFSS and Ansoft’s other EM tools, so more material parameter fields are available than are necessary for HFSS material definition n USE CAUTION!!! Any changes made in this interface affect ALL projects using these material assignments!!