design flow section 2: projects, hfss...

smart software for high-frequency design2-1

Ansoft HFSS Version 7Training

Section 2: Projects, HFSSDesign Flow


SynopsisThe Project Manager

DefinitionsDirectoriesProject Configuration Management

The HFSS Executive LevelExecutive Window

HFSS Design Flow StagesPre-processingSolutionPost Processing


The Maxwell Project Manager■ Analytical modeling

efforts using Ansoftsoftware are referred toas “projects”

■ A “project” consistsof files which define amodel, files whichcomprise its solution,and all files whichcomprise datagathered from thatsolution

■ Projects are created,accessed, andmanaged via theProject Manager buttonon the main Maxwelltoolbar

Starting the Maxwell Toolbar:

PC: Use shortcut or Run: “maxwell.exe”from install directory

UNIX: Type “maxwell &” in Xterm window


The Project Manager Interface

The Project List:Create, Rename,Copy, Move, andDelete Projects

The Directory List:Manage Directoriesand Directory Aliasesfor Project Storage

Data regardingthe currentlyselected project

Open the currentlyselected project

Recover selectedproject from anyinterrupted condition


Project Manager Basics■ Project Directories can be existing disk directories on your hard

drive, or created as subdirectories to existing directory structure■ Do not confuse a “Project Directory”, which contains many projects, with

“the project’s directory”, the folder containing all the files for a singleproject. The latter will have the form “projectname.pjt”

■ When moving or copying projects, begin in the destination directory■ Move and copy permits you to browse to the location of the source;

where the command was begun defines the directory the operation willmove/copy the project to.

■ A project’s files are managed so that the setup files must go with anyexisting mesh and solution data!!!

■ This is intentional, to preserve the configuration from which any solutionwas derived.

■ Editing a project’s setup files may delete meshes and solutions!■ To create a variation of an existing solved project, copy the original, and

work on the copy!■ Recover should unlock projects in the event of access errors■ Reclassify allows updating of projects to newer versions of the same

software


HFSS Executive Window

■ This is the startingwindow seen whenopening an HFSSProject.

■ The checklist at theleft accesses projectconstruction stepsand reflects currentstatus.

■ Buttons on thechecklist reflect theHFSS project designflow

Design Flow Checklist

Executive Display Options

Executive Display Window

Model View Display Options

Solution Monitoring Window NOTE: All 3D Display windows in HFSS will have aBLACK background. This is not currently editable inHFSS Version 7. Graphical window images havebeen inverted for this and all subsequent trainingpresentations for better paper reproduction.


HFSS Design Checklist

1. Define type of project

Driven is excited Eigenmode is not

2. Construct the geometry to be analyzed.

3. Define materials used in the model.

4. Define boundary conditions and source excitations for the model

(Optional Step: Define outputparameters for emissions

problems; access ports-onlysolutions.)

5. Set up solution parameters

6. EXECUTE SOLUTION!

7. Review results of analysis Matrix Data and Plot access S-parameters, etc. Fields accesses field visualization and calculations


HFSS Analysis Design FlowExecutive Window ‘checklist’ reflects 3 stages of Project designflow

■ PRE-PROCESSING■ All steps necessary to define the problem space and its characteristics

■ Geometry Construction■ Material Assignment (set Volume conditions)■ Source/Boundary Assignment (set Surface conditions)■ Solution ‘setup’ (desired frequency range, convergence, etc.)

■ SOLUTION■ The actual solution of the problem defined in Pre-Processing above.

Most of this step is ‘automatic’■ Excitation Solution■ Meshing and Matrix Solution

■ POST-PROCESSING■ Evaluation of the results of the model

■ Plot S-parameters, other circuit parameters, field quantities, etc.■ Generate antenna patterns, RCS response, etc.


HFSS Analysis Design Flowchart

Construct Geometry

(User Input)

Define VolumeConditions

(User Input)

Define SurfaceConditions

(User Input)

2D Excitation Solution

(Automatic)

3D Mesh Generation

(Automatic, User InputOptional)

Solve 3D Matrix

(Automatic)

View/Plot S-Parameters

(User Input)

View/Plot Fields

(User Input)

PRE-PROCESSING SOLUTION POST-PROCESSING

Define SolutionRequirements

(User Input)


Pre-Processing: Geometry Definition

HFSS solves for FieldBehavior

■ Therefore, Geometry mustinclude all volumes inwhich E- and H- fields willexist

■ Metals may be treated assurface conditions only;thickness need not bemodeled if penetration isnegligible effect (thickness> skin depth)

Example: For a WaveguideTee, we model the airinside, NOT the actual metalwall and flanges

Actual Structure

ModeledGeometry

(interior air)


Pre-Processing: Geometry Definition, cont.

■ Geometry Example Two: ForAntenna Structures, ModeledGeometry must contain somevolume of air/dielectric intowhich fields are intended toradiate

■ Pictured Model is 1/4 of acorrugated conical hornantenna; contained air shownas wireframe view

■ Note: Model would also bevalid without metal horn ‘wall’present!

■ Wall merely makesboundary definition easier

Fed (Port) End

Interior Air andRadiationVolume


Pre-Processing: Material Assignment(Volume Conditions)

■ All volumes within the modeled spacemust have electromagnetic Materialcharacteristics assigned

■ Note: Objects created as 2Dsurfaces can not have materialassignments, as they have novolume.

■ Volumes given dielectric propertieswill have interior field behavior solved.Volumes given conductive propertieswill most often NOT have interior fieldbehavior solved.

■ An impedance boundarycondition will be applied to theirexterior surface instead (seenext slide)

■ User option to solve inside forsemiconductors, thicknessconsiderations

Metal inner conductorvolume left in model,

but interior not solved

Dielectrics and airinside coax

contains fields

(Outer conductorvolume not modeled;surface conductivitycondition applied toexterior of dielectric

in next step)


Pre-Processing: Geometry Implications ofMaterial Assignment

■ Since all volumes in the modelreceived material assignments,care must be taken to preventconflicting assignments resultingfrom overlapping objects.

■ Volumes may be‘interlocking’, but notpenetrating one another’ssurface

■ Volumes may be whollycontained by other volumes

■ Volumes which intersectprevent the software fromdetermining which materialapplies for the intersectedregion

■ The 3D geometry modeler will testand warn if overlaps are found

LEGAL: Cylinder nestsinside ‘hole’ in box (shown

offset for clarity)

LEGAL: Cylinder split intotwo pieces: one inside and

one outside box

ILLEGAL! Cylinder andbox volumes intersect:

which material conditiontakes priority in shared

volume???


Pre-Processing: Boundary Assignment(Surface Conditions)

■ Both interior and exteriorsurfaces of a model mayhave boundary conditionsapplied

■ Boundary Conditionsinfluence the way thefields propagate in thesurrounding volume

■ Used to simulate metals,thin-film resistors, ‘free-space’ radiation, or fieldsymmetry conditions

■ Example: A model of amicrostrip line might use aconductive boundary torepresent the metal traceand ground plane

Ground Plane modeledby applying conductiveboundary condition to

bottom face of substrate

Dielectric substrateand air abovecontain fields

Filter Trace modeledas 2D object with

conductive boundarycondition

Symmetry conditionbisects model along

center of trace


Pre-Processing: Boundaries, cont.(Excitation Surface Conditions)

■ To solve for field behaviorwithin a structure, thebehavior must be excitedby some input signal

■ Inputs are applied asboundary conditions tosurfaces

■ Exceptions: Plane-waves(RCS) and Hint (ferritebiasing) apply to volumes

■ Example: The waveguidepropagating mode field isintroduced into the hybridmodel by assigning portexcitation boundaryconditions at the end faces

Port face, showingresulting field excitation

(4 ports total, onlyone shown)

Waveguide walls areconductive boundaries


Executive Parameters: Emissions Test

■ An Emissions Test allowscalculation of radiated fielddata for different excitationoptions during problemsolution

■ Radiated Fields can berequested for differentranges and surfaceprofiles

■ All ports and modes inthe problem can beexcited in anycombination

■ Radiation can becomputed for any desiredangular step in phi andtheta

NOTE: For many HFSS Users, the Emissions Test setup is rarely used.However, for EMI/EMC analysis (radiated emissions, radiatedsusceptibility, etc.) the Emissions Test setup is very important.

The Solution Setup presentation will discuss the fact that field data isonly saved for the final frequency of a Discrete Sweep, making Emissionevaluation at different frequencies difficult ‘after the fact’. The EmissionTest setup permits gathering of radiated field data while the 3D solution isbeing processed at each frequency of a Discrete sweep.


Solution: Solution Setup

Provide the desired solution criteriaFrequency for Solution

■ Frequency for Adaptive Solution Process■ Frequency Range for Sweeps

Convergence Criteria■ Acceptable “Delta-S”■ Maximum Number of Adaptive Passes

Type of Solution Desired■ Ports Only (excitation parameters only), or■ All (full 3D structure solution)■ Impedance only (to fill in alternate impedance

definitions)

Pressing the “Solve” button begins theprocess defined by the above specifications


Executive Parameters: Port Impedances

Interface is visuallyidentical to boundaryassignment moduleProvides quick accessto Port Solution FieldDisplays

■ Use after at least a“Ports Only” solutionhas been performed

■ Verify excited modalfield pattern isintended one beforeevaluating 3Dsolution data


Post-Processing: S-Parameters

■ S-Parameters, Impedances,and Propagation Constantscan be viewed in tabular orgraphical form

■ Cartesian and Smith Charts■ S-Parameters can be

manipulated to provide otherdata

■ “Deembedding” changesreference plane locations

■ “Renormalization” changesimpedance reference forcomparison to measurementsor export to circuit tools

■ Y- and Z-matrices can becalculated, displayed, andplotted


Post-Processing: Field Visualization

■ Field Quantities may beviewed in magnitude andvector form, both assnapshots andanimations

■ Calculations upon solvedfield quantities can beperformed and theirresults plotted

■ Far-Field data (radiation,RCS patterns) can begenerated and plotted

■ Example Shown: Mag-Eon substrate and AntennaGain Patterns for CPW-fed Patch

design flow section 2: projects, hfss...

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