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1、Section 7: Solution SetupGetting Started: Ansoft HFSS 8.0SynopsisThe Solution Setup WindowGeneral OverviewDriven Solution LayoutEigensolution LayoutDriven Solution Settings and GuidelinesFrequency and Adaptation CriteriaSweep SettingsMesh SettingsSeeding and Manual RefinementOutput OptionsEigensolut

2、ion Settings and GuidelinesFrequency and Adaptation CriteriaMesh SettingsMonitoring the Solution in ProgressThe Solution Setup Window (Driven)Single Frequency and Adaptation Settings Frequency, Pass Count, Tet Refinement, Convergence RequirementsSweep Settings Sweep Type, Range,and PointsMesh Option

3、s Starting Mesh, Initial (Lambda Refinement, Seeding) and Manual (Graphical-based Refinement) Meshing OptionsSolution Type Full 3D problem or2D ports/impedancesonlyPort Soln. Settings Field Data save options,Port Field Accuracy settingThe Solution Setup Window (Eigenmode)Starting Frequency and Eigen

4、mode Settings Frequency, Number of Modes DesiredMesh Settings Starting Mesh, Initialand Manual meshingcriteriaAdaptation Control Pass Count, Tetrahdral Growth Limit, Convergence CriteriaDriven Solutions: Adaptation and ConvergenceSolution adaptation is performed at a single frequency specified by th

5、e user.Model behavior is explored systematically by solving gradually denser meshesMesh density is added where necessary, not indiscriminatelyAdaptation progress is evaluated against the solution convergence criteriaCriterion 1: Number of PassesCriterion 2: Acceptable maximum Delta-S.Maximum Delta-S

6、 is the worst-case vector magnitude change of any S-parameters solution from Pass N as compared to its solution from Pass (N-1).Per-Parameter criteria also available95% of HFSS Project Setups Should Use at Least Some Adaptation!Note how mesh density is greater in the region between filter posts, whe

7、re wave energy is superposed by reflectionsFilter PostsDriven Solutions: Tetrahedral RefinementTetrahedral Refinement is based on percentage of the prior meshThis maintains a consistent “l(fā)ever arm” for solution changesIf the mesh is permitted to grow too quickly, subsequent solutions may be accurate

8、, but take excessive computational resources and timeIf the mesh is permitted to grow too slowly (e.g. a fixed tet growth count, rather than percentage), the “l(fā)ever arm” shrinks with respect to the problem, and solutions may appear to artificially converge before true behavior is representedThe defa

9、ult Tet. Refinement value is 20%. This is adequate for the vast majority of HFSS projects.Convergence data below is shown for a model usingthe default 20% tetrahedral refinement criterion. Had the number of new tetrahedra been kept level, the solution would likely have exited on or around Pass 5.Dri

10、ven Solutions: Where to Adapt?Proper adaptive frequency selection is very important to solution accuracyInitial mesh and subsequent adaptation are in part wavelength dependantDespite convergence, the mesh may be too coarse for good results at frequencies with a significantly smaller wavelength.Adapt

11、ive frequency mendations:For single-frequency or narrow-band solutions (insignificant change in ): Adapt at frequency of interestFor wide-band solutions: Adapt between the middle and high ends of the band (smaller wavelength)Caution: If you want to view behavior over a specific band, but the devices

12、 response is more narrow, adapt within the devices bandwidthFor this band-pass filter, adapting here will result in mesh refinement inside the filter structure, capturing its behavior.while adapting here may only permit tetrahedral refinement at the ends of the filter, where the energy is beingrejec

13、ted.Driven Solutions: Frequency SweepsDiscrete frequency sweeps perform full matrix solutions at each pointThe mesh resulting from the adaptation process is usedExcitation is reset to each frequency for the full matrix solutionOnly the LAST solutions field data is preserved for post-processing!Fast

14、frequency sweeps perform an ALPS analysisFrequency behavior is computed from reduced matrices, using the Lanczos methodA Pad approximation fills in the total number of requested frequency pointsField data across the entire bandwidth is preserved for post-processing!Break-even in solution time is gen

15、erally 8-10 frequency points (paging neglected)The FAST sweep is capable of providing up to 999 frequency data points. Since this is the number of points used in the Pade curve-fit, and NOT the number of solutions performed, in most cases its worth your time to use them.The DISCRETE sweep, although

16、used for fewer frequency steps due to the full matrix solution at each step, does allow custom, point-by-point editing of desired solution frequencies.Driven Solutions: Mesh SelectionSolutions can begin with several different meshesFor the first solution performed, the initial mesh is generally used

17、Initial mesh uses lambda refinement by default, and can also utilize seed refinementIf one or more adaptive passes have been previously solved, at the same or a different adaptive frequency, the current or previous mesh may also be selectedCurrent allows continuation of the adaptation process if the

18、 desired number of passes was reached before the desired delta-S value.Previous allows the user to take a step back from an overly large meshFor the first or subsequent solution(s), the user may elect to create a manual meshThe Mesh Options button allows further definition for either the Initial or

19、the Manual meshesInitial Mesh Options: SeedingLambda Refinement is the default initial mesh settingThe mesher will assure that tetrahedral edge lengths are on the order of /4The Define Seed Operations button accesses the graphical meshing interfaceHere, the user selects objects, object faces, or box

20、 subregions within the model to apply mesh seedingSeeding is application of additional vertices with a specified separation within the modelSeeding is acted upon when the solution process begins meshing the projectInitial Mesh Options: Seeding ProcedureSelect an object, face, or combination thereof

21、in which a seeding parameter is desired.From the Seed menu, select Object to seed the volume, or Object Face to seed faces onlyBox does not require prior object selection; the interface will instead prompt for the box location in which to apply seeding.Define whether seeding should be by (tet edge)

22、length, (triangular face) area, or (tetrahedral) volume.Define seed dimension (in the active drawings units) and tetrahedral count restraints.Manual Mesh Options: The Manual MesherTo create a Manual Mesh, first select the mesh upon which to base itOptions will be the same as those available f

23、or solution, depending on the projects current statusThe Define Manual Mesh button activates the graphical meshing interfaceThis is the same interface used for mesh seeding. However, in Manual Mesh mode the seeding operations are disabledThe interface is used to directly generate a mesh based on use

24、r inputsManual meshing options are identical to the seeding optionsManual Mesh Options: ProcedureSelect an object, object face, or combination thereofFrom the Refine menu, pick whether you want to refine the mesh in the object volume or on its facesBox requires no prior geometry selectionSelect whet

25、her to refine by length, area, volume, etc.Provide refinement dimensional criteria and mesh growth restrictionsContinue through all objects to be manually refinedNOTE: Since you are generating a MANUAL mesh, Lambda Refinement will NOT be performed on any objects you neglect!.Seeded or Manual

26、Meshing: Why Bother?Some model types do not solve efficiently using adaptive refinement alone; these options can speed convergenceHigh Dielectric Constants: Materials with a high dielectric constant solve better if seeded or manually meshed within the dielectric, due to the significantly smaller wav

27、elengthLocally Strong Field Gradients: Some structures, such as the capacitively-loaded cavity on the lower left, have features whose influence on the behavior is not wavelength-drivenExtreme Aspect Ratios: Models with very high aspect ratios are harder to mesh with high quality tetrahedra; manual o

28、r seed-based assistance can improve the mesh quality and resultant matrix conditionCylindrical Dielectric Resonator in Cavity. Dielectric Puck has r = 90. Wavelength is only 1/10 that in surrounding air volume! Seeded to /4 in the material to compensate.Cavity structure at right has post extending f

29、rom bottom to almost touch the top. The narrow capacitive gap between the post end face and the cavity end itself has a virtual solid defined to allow manual meshing where fields will be very strongSolution Output OptionsSpecify Solution Type:All is entire 3D matrix solutionPorts Only performs the c

30、omplete 2D eigensolution at the portsImpedance Only provides updated impedance calculations to an already-performed solution, after changes/additions to impedance linesPort Solution Options:Save Fields button allows selection of All, Dominant, or First N ModesS-parameters for all ports and all modes

31、 are provided regardless. This setting only determines what field data is preserved following solutionIf First N Modes is selected, the number for which fields should be saved is entered in Max Modes fieldField Accuracy sets the accuracy level for the Port Field solution. Increase only if necessary

32、to lower the noise floor of the port solutionUse Caution! Excessively tight settings increase the entire 3D mesh size.NOTE: “Emissions Only” solution is only available following a fast sweep. For a discrete Emissions test, select “All” to perform with the full matrix solution.Eigenmode Settings: Ada

33、ptation and ConvergenceLike the Driven Solution, Eigenmode setup permits adaptation and convergenceUser specifies Minimum Frequency above which to begin seeking resonant eigenmodes, and number of modes to discoverAdaptation criteria is by Pass Number, or to Delta Frequency resultsSolution will conti

34、nue until frequencies stabilize to desired level or maximum number of passes is reachedTet. Refinement percentage operates much as with a Driven solution, but is not tied to a specific frequency or eigenmodeEigenmode Settings: Meshing OptionsEigenmode Solution Starting Mesh selection and Initial and

35、 Manual Mesh Options are identical to those for driven solutionInitial Mesh Options accesses the mesh seeding interfaceManual Mesh Options accesses the graphical mesher for direct user-refined meshingSolution Setup Exercise 1. Find the project named “sln_exer” in the Project Manager, and Open it. Th

36、e view of the geometry should be familiar; this project is a copy of the model we performed the Boundary/Source Setup exercise on.2. Select Setup Solution. to access the Solution Setup screen, and enter the settings identified in the steps below.3. Single Frequency: Checked Value: 20 GHz4. Adaptive:

37、 Checked Requested Passes: 6 Tet. Refinement: 20%5. Max Delta S: Selected Value: 0.016. Sweep: Checked (fast) Start Frequency: 14 GHz Stop Frequency: 22 GHz Num. Steps: 9997. Move down to the Mesh Options dropdown and press it to select Initial Mesh.Proceed to the next page..5.6.7.Solution Se

38、tup Exercise: Mesh Seeding 1. In the Initial Mesh Refinement options box, leave Lambda Refinement selected and press the button for Define Seed Operations.2. From the Edit menu of the graphical mesh interface which launches, pick Select (or use the selection tool button).3. Select the 2D “trace” obj

39、ect, and close the selection dialog.4. From the Seed menu, pick Object Face.By Length. Since “trace” is a 2D object we can seed on its face only, and we have chosen to do so by tetrahedral edge length..5.5. A refinement dialog box will open. Uncheck the box beside Maximum number of elements t

40、o be added. This deselects tet numbering limits on the seed value.6. Beside the Maximum Element Length title enter the number “10” in the field provided. This is the maximum edge length for any tetrahedra which has a face on the “trace” object.7. Press OK to close the dialog.6.7.Solution Setup Exercise: Seeding, cont. 1. Because we are defining seeding rather than performing an immediate mesh refinement, we do not see any changes. However we can view any stored information by picking Seeding Info from the Seed menu.2. Aft