Topics: Ansoft HFSS — Setup Solution Setup Solutionread.pudn.com/downloads107/ebook/442805/hfss/solopt.pdf · Topics: Ansoft HFSS — Setup Solution Go Back Contents More Index

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specified, choose Setup

f solutions are available:

tion. Optionally, you can .asses, solution frequency odes of the solution are cted type of solution.

onstruct a problem with-an generate a field solu-ommands dealing with

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Ansoft HFSS — Setup Solutionics:

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Setup SolutionAfter material attributes, boundaries, and sources have beenSolution to:

• Select the type of solution to be performed. Three types o• Adaptive solution • Non-adaptive solution • Frequency sweep

• Select the finite element mesh to be used during the soluseed the mesh to make it more dense in areas of interest

• Specify solution criteria, such as the number of adaptive p(or frequencies), error tolerances, and whether multiple msaved. The criteria you specify are determined by the sele

Note: Because voltage and current sources allow you to cout ports (and thereby without S-parameters), you ction without calculating S-parameters. As a result, cports and S-parameters will be disabled.

up Solutionrvieweral Procedurele Frequency

imum Frequencyimum Number of Eigen-desptiveptive Criteriaepting Meshe Selections

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ell Online Help System 328 Copyright © 1996-2002 Ansoft Corporation

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rge region is a fairly difficult nomial expression that cov-HFSS is to use finite ele-ller regions (tetrahedra)

largely transparent to users ensure that the field solution sources.

of tetrahedra. To obtain val-e nodal values of the finite

the mesh:

t be interpolated accurately. mild would have similar gradient region. Since the ts prior to solving the

apidly, the fields inside it

mputational effort exactly s one that has enough tetra- that the available comput-

rated for a structure is rarely to be divided into more tet-

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OverviewRepresenting an electric or magnetic field over a relatively latask. Fields cannot be accurately described with a single polyers the entire problem region. The approach taken by Ansoft ment analysis to subdivide the problem region into many smawhere fields may be accurately computed.

Need for a Fine MeshAlthough this implementation of the finite element method is of the software, a general understanding of it is necessary to is as accurate as possible for a given amount of computing re

Ansoft HFSS computes electric fields at the nodes (vertices) ues for the field at other points, it interpolates the field from thelement mesh.

There are a number of factors that facilitate the need to refine

• If the tetrahedra are too large, the fields inside them cannoA large tetrahedron located where the field gradients are interpolation error to much smaller tetrahedra in a strong software does not know the location of the strong gradienproblem, the initial meshes are seldom adequate.

• If the field in the vicinity of a tetrahedron is changing too rcannot be interpolated accurately.

The meshmaker relies on adaptive refinement to focus the cointo regions that require it. The optimal mesh for a structure ihedra to accurately represent a field solution but not so manying resources are overwhelmed. The initial mesh that is genethe optimal mesh. The mesh must be refined — that is, it hasrahedra.

p Solutionrvieweed for a Fine Mesheshmaker Sizing Limits Min D)eral Procedurele Frequencymum Frequencyimum Number of Eigen-desptiveptive Criteriaepting Meshe Selections Solutionults


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ly in regions where the error during an adaptive field e refinement. mesh is refined. This is .

mesh.

D as the foundation for con-

that is small enough so that tly, Min D is set to be 10-7 tance between two points is

D. For example, a point is the point to the plane is

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The Setup Solution command lets you control the mesh refitwo ways to accomplish this task:

• Adaptive mesh refinement. This refines the mesh iterativeis high. You set the criteria that controls mesh refinementsolution. Many problems can be solved using only adaptiv

• Manual mesh refinement. You explicitly specify where theuseful when you know where high-error areas are located

Use either strategy or a combination of both to best refine the

Meshmaker Sizing Limits (Min D)Like the 3D Modeler, the Meshmaker uses the concept of Minstructing the finite element mesh.

Min D is defined to be the distance between a point and a linethe point may be considered to be resting on the line. Currentimes the smallest dimension of the problem region. If the dissmaller than Min D, the points are considered coincident.

The tolerance used in geometry calculations is based on Minconsidered to be on a plane if the perpendicular distance fromsmaller than Min D.

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em being solved. The follow-w to specify the solution cri-

rocedure:

Executive Commands

cedure:

tive one in which the sys-ell’s equations. In gen-eria for the first few field e stopping criteria need

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General ProcedureThe solution criteria used depend heavily on the type of probling general procedure is meant to give you a basic idea of hoteria.

Driven Solution Setup> To specify solution criteria for a problem, follow this general p

1. Specify the following as applicable:

2. Choose OK to save the solution criteria and return to the window.

Eigenmode Solution Setup> To specify solution criteria for a model, follow this general pro

1. Specify the following as applicable:

• Single frequency• Adaptive solution criteria• Sweep type and criteria• Starting mesh• Solve type• Setup for full-wave Spice• Port solution criteria

Note: The process of computing a field solution is an iteratem converges on a field pattern that satisfies Maxweral, accept the default stopping and refinement critsolutions. Then, check their convergence to see if thto be adjusted.

• Minimum Frequency• Maximum Number of Eigenmodes• Adaptive solution criteria• Starting Mesh

up Solutionrvieweral Procedureriven Solution Setupigenmode Solution etuple Frequency


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2. Choose OK to save the solution criteria.

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ptive solution at a single fre-Frequency field.

s and their conversion

nmode solver begins the cified number of modes with

enmode solutions that the e eigenmode solutions

alize some matrices, if g to solve a nearly-sin-

alculations. As a general he suggested, or default,

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Single FrequencyDriven Solutions only.

Select Single Frequency to generate an adaptive or non-adaquency. Specify the desired solution frequency in the Single

> To change the frequency units:1. Choose Freq. Units. A window appears, listing frequencie

factors.2. Select a frequency from the list. 3. Choose OK.

The selected frequency unit is the new unit.

Minimum FrequencyEigenmode Solutions only.

The Minimum Frequency is the frequency at which the eigesearch for eigenmodes. The solver searches for the user-spea higher resonant frequency than the Minimum Frequency.

Maximum Number of EigenmodesEigenmode Solutions only.

The Maximum Number of Eigenmodes is the number of eigsolver finds. If you enter five, the solver calculates the first fivabove the Minimum Frequency.

The solver can only find up to 20 eigenmode solutions.

Warning: Because the Minimum Frequency is used to normthe frequency is set too low, the solver ends up tryingular matrix, which may erode the accuracy of the crule, do not enter a frequency less than 0.01 times tvalue for the Minimum Frequency.

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of the solution process. An hen you select an adaptive

s of the frequency,

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AdaptiveSelect Adaptive to iteratively refine the starting mesh as partadaptively refined mesh increases the solution’s precision. Wsolution, you must specify:

For a Driven Solution:• the frequency at which to generate a solution and the unit• any adaptive refinement information, • the starting mesh, • the solution to perform, • the port solution criteria, and • the parameters you wish to Solve. For an Eigenmode Solution:• the minimum frequency at which to generate a solution,• the number of eigenmodes,• any adaptive refinement information, • whether or not to perform a Real Frequency Convergen• the starting mesh.

p Solutionrvieweral Procedurele Frequencymum Frequencyimum Number of Eigen-desptiveon-Adaptiveptive Criteriaepting Meshe Selections Solutionults


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using the starting mesh. ist inside the structure ing a frequency sweep, gle Frequency.

convergence criteria are

sed on the current finite problem domain where gions are refined. system recomputes the nce criteria are satisfied d.

olves the problem at the

one solution at the selected st specify:

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In general, an adaptive field solution follows this process:

1. After Solve is chosen, Ansoft HFSS generates a solution 2. Ansoft HFSS computes the electromagnetic fields that ex

when it is excited at a single frequency. If you are also doan adaptive solution is performed only at the specified Sin

3. The system stops the adaptive solution process when themet.

4. The system selectively refines the finite element mesh. Baelement solution, the system estimates the regions of thethe exact solution has strong error. Tetrahedra in these re

5. Another solution is generated using the refined mesh. Theerror, and the iterative process repeats until the convergeor the requested number of adaptive passes are complete

If a frequency sweep is being performed, Ansoft HFSS then sother frequency points without further refining the mesh.

Non-AdaptiveSelect Single Frequency and deselect Adaptive to generatefrequency. When you select a non-adaptive solution, you mu

• the frequency at which to generate a solution and the unit• the starting mesh, • the solution to perform, and • the port solution criteria.

A non-adaptive solution does not refine the mesh.


imum Frequencyimum Number of Eigen-desptiveon-Adaptiveptive Criteriaepting Meshe Selections

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s and stopping criteria.

aptive solution. If the num-lution stops. Otherwise, the

reached.

hat you would like Ansoft ld. Initially, use a value ement cycle when the num-

are added after each itera-g 10 causes the mesh to th the highest error will be dra would be refined so that ccept the default value.

lete in the preferences e in the Solution Setup zero, it will not override

nt of memory required to inement of the mesh. in the system requesting time to compute solu-


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Adaptive CriteriaFor an adaptive solution, specify the solution pass parameter

Requested PassesThe Requested Passes field is a stopping criterion for the adber of requested passes has been completed, the adaptive sosolution process continues until the convergence criteria are

To specify the maximum number of mesh refinement cycles tHFSS to perform, enter a value in the Requested Passes fiebetween 3 and 5. The system breaks out of the adaptive refinber of requested passes is met.

Tet. RefinementThe Tet. Refinement field determines how many tetrahedra tion of the adaptive refinement process. For instance, enteringrow approximately 10 percent each pass. The tetrahedra wirefined. If your mesh consisted of 1000 elements, the tetrahe100 new elements would be added to the mesh. Generally, a

Note: If you define a minimum number of passes to compfile, it will override the Requested Passes field valuwindow. If the value in the preferences file is set to the Requested Passes field value.

The size of the finite element mesh — and the amougenerate a solution — grows with each adaptive refSetting the Requested Passes too high can result more memory than is available or taking excessive tions.


imum Frequencyimum Number of Eigen-desptiveptive Criteriaequested Passeset. Refinementax Delta Satrix Convergenceax Delta Eaximum Delta Fre-uencyeal Frequency Conver-ence Onlyepting Meshe Selections

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solution. If the magnitude n the specified Max Delta S ops. Otherwise, the solution mpleted.

m continues to refine the ntil the magnitude of the


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Max Delta SIf ports exist.The Max Delta S field is a stopping criterion for the adaptive and phase of all S-parameters change by an amount less thaamount from one iteration to the next, the adaptive solution stprocess continues until the requested number of passes is co

For example, if you specify 0.1 as the Max Delta S, the systemesh until the number of requested passes is completed or ucomplex delta of all S-parameters changes by less than 0.1.



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d.ping parameter for the

ing:

ce. once. the matrix entries by click-atrix entries are outlined.

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Matrix ConvergenceIf ports exist.

> To specify a different stopping criteria for each S-parameter:1. Select Matrix Convergence. The Matrix button is enable2. Choose Matrix. The window for specifying a different stop

phase and magnitude of each S-parameter appears:

3. From the Entry Selection options, select one of the followAll Sets all the matrix entries at once.Diagonal Sets all the diagonal matrix entries at onOff-Diagonal Sets all the off-diagonal matrix entries atIndividual Sets individual matrix entries. You select

ing on them with the mouse. Selected m

p Solutionrvieweral Procedurele Frequencymum Frequencyimum Number of Eigen-desptiveptive Criteriaequested Passest. Refinementax Delta Satrix Convergenceax Delta Eaximum Delta Frequencyeal Frequency Conver-ence Onlyepting Meshe Selections Solutionults


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Topy selecting one of the

nge for the magnitude of

for the phase of the

ed matrix entries. criteria for each

e finite element mesh until e and phase of all S-param-

olution when ports have not y. This convergence criteria lution converges, this term he system refines the mesh ears on screen represents

hen the Delta E falls below

mode matrix entries. Use Diagonal.der mode matrix entries. Off-Diagonal.


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4. Optionally, you may further refine the selection process bfollowing from the Mode Selection options:

5. In the Magnitude field, enter the maximum allowable chathe selected matrix entries.

6. Select Use dB if you are specifying the magnitude in dB.7. In the Phase field, enter the maximum allowable change

selected matrix entries. Phase is entered in degrees.8. Choose Set to set the magnitude and phase of the select9. Choose OK when you are finished specifying the stopping

S-parameter.

With these settings in effect, the system continues to refine ththe number of requested passes is met, or until the magnitudeters change by an amount less than the specified criteria.

Max Delta EVoltage and current sources only, without ports.

The Max Delta E field is a stopping criterion for the adaptive sbeen defined. The error is a measure of the solution’s accuracis based on the change in a computed energy term. As the soapproaches a constant value and Delta E approaches zero. Tin tetrahedra that have the largest error. The Delta E that appthe Delta E for all tetrahedra.

The system breaks out of the adaptive refinement process wthe specified value.

Dominant Only Select this to set only the dominantthis only with All, Diagonal, or Off-

Higher Order Only Select this to set only the higher orUse this only with All, Diagonal, or



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for the adaptive solution sed on the change in the

of the solution’s accuracy.

d for one mesh, then the for the refined mesh. Ansoft quency of the first mesh and r the set of five frequencies. (expressed as a percent) is requency differences is less ed.

en the largest frequency dif- value.

percent difference calcula- of the frequencies only; the


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Maximum Delta FrequencyEigenmode Solutions only.

The Maximum Delta Frequency field is a stopping criterion when solving for Eigenmodes. This convergence criteria is bacomputed frequencies for each eigenmode and is a measure

For example, assume five resonant frequencies are calculatemesh is refined, and five resonant frequencies are calculatedHFFS calculates the difference between the first resonant frethe first resonant frequency of the refined mesh and so on foThe greatest difference among the five frequency differencesthe delta frequency. If the greatest difference among the five fthan the Maximum Delta Frequency, the problem is converg

The system breaks out of the adaptive refinement process whference falls below the specified Maximum Delta Frequency

Real Frequency Convergence OnlyEigenmode Solutions only.

When you choose Real Frequency Convergence Only, thetion among a set of frequencies will be based on the real partsimaginary parts of the frequencies are ignored.



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ncies. You may choose to n for each division within a ns at specific frequency timates a solution for an s save circuit parameters at

tions.

ange operation in the fre-tion of the behavior near the cantly greater than the time

ecessary to accurately rep-a discrete sweep is the time ber of frequency points.

and the frequency response eed your resources. An iscrete sweep’s because a n solutions for a minimal n interpolating sweep is the maximum number of solu-

ross cut-off in the fre-ears listing the port and


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SweepDriven Solutions only.

Select Sweep to generate a solution across a range of frequeperform a fast sweep that generates a unique full-field solutiofrequency range, a discrete sweep that generates field solutiopoints in a frequency range, or an interpolating sweep that esentire frequency range. Both discrete and interpolating sweepeach requested frequency but discard intermediate field solu

Choose a fast sweep if the model will abruptly resonate or chquency band. A fast sweep will obtain an accurate representaresonance. The time required for a fast sweep may be signifirequired for a single frequency solution.

Choose a discrete sweep if only a few frequency points are nresent the results in a frequency range. The time required for required for a single frequency solution multiplied by the num

Choose an interpolating sweep if the frequency range is wide is smooth, or if the memory requirements of a fast sweep excinterpolating sweep’s time requirement is much less than a dsolution for the entire frequency range is interpolated based onumber of frequency points. The maximum time required for atime required for a single frequency solution multiplied by thetions.

Note: When performing a fast sweep, no port mode may cquency range. If this occurs, an error message appmode violating this condition.


imum Frequencyimum Number of Eigen-desptiveptive Criteriaep

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lect a fast frequency sweep,

center frequency of the fre-ith which to generate a solu-os-Padé Sweep (ALPS)- sted frequency range from

hile the S-parameters are teps. However, the fast frequency entries to the

d during an adaptive solu-aptive solution, the initial rther refinement. Also, the pending upon the desired , you may wish to perform

nter frequency if the Sin-er than the Start Fre-wise the middle of the


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FastSelect Fast to request a fast frequency sweep. When you seyou must specify the following:

• the solution to perform,• the frequency units,• the frequency range • the number of sampling steps, and• the starting mesh.

If you request a fast frequency sweep, Ansoft HFSS uses thequency range to select an appropriate eigenvalue problem wtion for the entire fast sweep. It then uses an Adaptive Lanczbased solver to extrapolate the field solution across the requethe center frequency field solution.

The full-field solution is saved only at the center frequency, wsaved for every frequency point specified by the number of ssweep allows the 3D Post Processor to display fields for any sweep range.

Be aware that the system uses the finite element mesh refinetion at the Single Frequency or, if you did not request an admesh generated for the problem. It uses this mesh without fufield solution at the center frequency is the most accurate. Delevel of accuracy you require throughout the frequency rangeadditional fast sweeps at other center frequencies.

Note: Ansoft HFSS uses the Single Frequency as the cegle Frequency is within the frequency range (greatquency and less than the Stop Frequency). Otherfrequency range is used as the center frequency.




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d the information is saved in main problem. Emissions t sweep solution.


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Fast Sweep and Emissions TestOnce a field solution has been generated for a fast sweep ana file, an emissions test can be performed independent of thedata is calculated based upon information saved from the fas




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n you select a discrete fre-

of frequencies to solve, and

icitly solves the field solution e range is 1000 MHz to 000, 1250, 1500, 1750, and d so that a new field solution saved for the final frequency 00 MHz. The S-parameters ency point. The more steps uency sweep.

d during an adaptive solu-aptive solution, the initial rther refinement. Because ingle Frequency, it is possi-ficantly far away from this o use the center of the fre-g the results, run additional ncies.

eep you must solve both at olution at each point. This nt and, before deleting that


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DiscreteSelect Discrete to request a discrete frequency sweep. Whequency sweep, you must specify the following:

• the solution to perform,• the frequency units,• the frequency range• either the number of frequency steps or the explicit choice• the starting mesh.

If you request a discrete frequency sweep, Ansoft HFSS explat each division within the frequency range. For example, if th2000 MHz, specifying four steps would result in solutions at 12000 MHz; however, the field solution for each point is deletecan be generated for the next point. The field solution is only point computed. In this case, the field solution is saved at 20and any emissions test information are saved for every frequyou request, the longer the system takes to complete the freq

Be aware that the system uses the finite element mesh refinetion at the Single Frequency or, if you did not request an admesh generated for the problem. It uses this mesh without futhe mesh for the adaptive solution is optimized only for the Sble for the accuracy of the results to vary at frequencies signifrequency. If you wish to minimize the variance, you can opt tquency range as the Single Frequency; then, after inspectinsolutions with the Single Frequency set to the critical freque

Discrete Sweep and Emissions TestWhen solving an emissions test with a discrete frequency swthe same time because an emissions test requires the field sway, the system generates a field solution at a frequency poifield solution, performs the emissions test.




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eep. When you select an :

S chooses the frequency erpolated solution lies within deleted so that a new field ution is only saved for the last frequency point com-

ecutive Commands window. ints, including the last y solved frequency point.

rance criterion or generates about the solution, increase

d during an adaptive solu-aptive solution, the initial rther refinement.

cy sweep you must solve field solution at each point.

y point and, before deleting test results are interpolated parameters.


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InterpolatingSelect Interpolating to request an interpolating frequency swinterpolating frequency sweep, you must specify the following

• the solution to perform,• the frequency units,• the frequency range,• the desired number of sampling frequency steps,• the starting mesh, • the error tolerance, and• the maximum number of solutions.

If you request an interpolating frequency sweep, Ansoft HFSpoints at which to solve the field solution so that the entire inta specified error tolerance. The field solution for each point issolution can be generated for the next point. The full-field solfinal frequency point computed. To view information about theputed, click on the Profile button in the display area of the ExScroll down to find information about the solved frequency posolved frequency point. The S-parameters are saved for ever

The sweep is complete when the solution meets the error tolethe maximum number of solutions. To view more information the number of steps and perform the sweep again.

Be aware that the system uses the finite element mesh refinetion at the Single Frequency or, if you did not request an admesh generated for the problem. It uses this mesh without fu

Interpolating Sweep and Emissions TestWhen solving an emissions test with an interpolating frequenboth at the same time because an emissions test requires theThis way, the system generates a field solution at a frequencthat field solution, performs the emissions test. The emissionsto the sampling frequencies in a manner similar to the circuit




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following sweep parameters:cy sweep.cy sweep.frequency range is divided. Frequency, 20 for Stop eps for a discrete sweep lution for frequencies of 10, of steps specified for an unt of information that will .wed between two succes-

lerance is specified for lt 0.5 percent is usually sat-

hat will be solved for the fre- is specified for interpolating


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Sweep ParametersIf you are performing a frequency sweep, you must enter the

Start Frequency The starting frequency of the frequenStop Frequency The ending frequency of the frequenNumber of Steps The number of steps into which the

For example, specifying 10 for StartFrequency, and 4 for Number of Stinstructs the system to compute a so12.5, 15, 17.5, and 20. The number interpolating sweep dictates the amobe viewed on a post-processing plot

Error Tolerance The maximum relative difference allosive interpolation solutions. Error tointerpolating sweeps only. The defauisfactory.

Maximum Solutions The maximum number of solutions tquency range. Maximum solutionssweeps only.




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points. The following win-

eep.

he list of frequencies.

f frequencies based on the

ndow that appears does frequency points.


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Viewing the FrequenciesChoose View/Edit Frequencies to view or edit the frequencydow appears when you choose this command:

Adding Frequency PointsUse the Insert command to add new frequency points to a sw

> To add a new frequency point:1. Enter the value of the new frequency in the Value field.2. Choose Insert.The new frequency point appears below the selected one in t

UniformUse the Uniform command to create a uniform distribution onumber of steps and the first and last frequency.

> To create a series of uniformly distributed frequency points: • Choose Uniform.

The new frequencies appear in the Frequencies list.

Note: For fast and interpolating frequency sweeps, the winot have the commands that allow you to modify the




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.

int.

encies.

int in the list of frequencies.

ither ascending or descend-

ding. This is the default

ending.

e list.


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Deleting Frequency PointsUse the Delete command to delete existing frequency points

> To delete a frequency point:1. Select the frequency point from the list of frequencies.2. Choose Delete.

The frequency is deleted and removed from the list.

Modifying Frequency PointsUse the Modify command to modify an existing frequency po

> To modify a frequency point:1. Select the frequency point to change from the list of frequ2. Enter the new value in the Value field.3. Choose Modify.

The old frequency point is replaced by the new frequency po

Sorting Frequency PointsUse the Sort commands to arrange the frequency points in eing order.

> To sort the frequency points: • To sort the points in ascending order, choose Sort/Ascen

setting. • To sort the points in descending order, choose Sort/Desc

Moving Frequency PointsUse the Move Up command to move a frequency point up th

> To move a frequency point: 1. Select the point to move from the Frequencies list. 2. Choose Move Up.

The frequency point moves to its new location in the list.




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S to PSpice, HSPICE, and pice analysis. A full-wave

n. If you plan to perform a window to help determine a

erse of the rise and fall requency sweep may have aximum frequency until the

quency be less than the . It is usually recommended

ghtly improve the full-wave ory requirements to solve vides a good trade-off

p for Full-Wave Spice ider frequency content range may miss some

um frequency during a dis-ilure of the port solver to

um frequency until the , the minimum frequency uency response deter-


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Setup for Full-Wave SpiceWhen you export terminal S-parameter data from Ansoft HFSMaxwell Spice software, you are able to perform a full-wave SSpice analysis includes full-wave effects in a circuit simulatiofull-wave Spice analysis, use the Setup for Full-Wave Spicesuitable frequency sweep range for the solution.

The maximum frequency should be at least five times the invtimes. If the specified frequency band is too wide, an HFSS fconvergence problems. If this happens, try to decrease the msolution converges.

It is recommended, though not required, that the minimum fremaximum frequency divided by the number of frequency stepsto have at least 500 frequency steps. A higher number will sliSpice solution accuracy, but will also increase CPU and memthe problem. For most cases, using 1000 frequency steps probetween the accuracy and computational requirements.

Note: The frequency sweep ranges suggested in the Setupanel are estimates. You may have a pulse with a wand Ansoft HFSS’s recommended frequency sweepof the high frequencies.

Warning: Occasionally, HFSS can fail to solve for the minimcrete or interpolating frequency sweep due to a faconverge. If this happens, try to increase the minimsolution process completes successfully. Howevershould be as low as possible because the low-freqmines the steady-state time response.



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ill be used for a full-wave

ndow. The Setup for

m rise time. This value change of the input time fault, this value is set to

efault, this value is set to


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p Solutionrvieweral Procedurele Frequencymum Frequencyimum Number of Eigen-desptiveptive Criteriaep

astiscreteterpolatingweep Parametersetup for Full-Wave piceting Meshe Selections Solutionults

Calculate> To determine a suitable frequency range for a solution that w

Spice analysis:1. Choose the Calculate button from the Setup Solution wi

Full-Wave Spice window appears:

2. Enter a value in the Signal Rise Time field for the minimurepresents the time scale that will characterize the rate ofsignal, which will be applied in the circuit simulator. By de1.

3. Enter a value in the Time Steps Per Rise Time field. By d5.


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lated using

ault, this value is set to using ,

imum Frequency using

.data to the frequency choose Cancel to return y entered frequency

N ∆t×

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astiscreteterpolatingweep Parametersetup for Full-Wave piceting Meshe Selections

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The time sampling increment for the entire signal is calcu

where• ∆t is the time sampling increment.• τ is the signal rise time.• Nτ is the number of time steps per signal rise time.

4. Enter a value in the Number of Time Points field. By def500. Note that the input time signal duration is determinedwhere N is the number of time points.

5. Select a unit of time from the pull-down menu.6. Choose Calculate. The software now determines the Max

where Fmax is the maximum frequency.

The software determines the Frequency Step Size using

and determines the Number of Frequency Steps using 7. Choose Accept to transfer the new frequency sweep

sweep fields in the Setup Solution panel. Optionally, to the Setup Solution window and maintain previouslsweep settings.

∆t τNτ------=

Fmax0.5∆t-------= ,

FmaxN

-----------


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the following to specify the

which is automatically cre-In general, you should per-itial Mesh. Because the

large, a non-adaptive solu- to be an accurate one.

used to improve the initial

h that was most recently adaptive analysis, choose been generated, selecting Initial Mesh.ed finite element mesh. To us Mesh as the starting

n adaptive solution, using rocessing time. When the pping criteria, then the sec-s the last mesh. If you view are satisfied with the S-ive pass, select Previous

al mesh with the Mesh-


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rting Meshelect the Meshesh Optionseciding on a Meshe Selections

t Solutionaults

Starting MeshFrom Starting Mesh, you may do the following:

• Select the mesh with which to start the solution process.• Manually refine the mesh.• View the number of tetrahedra in the selected mesh.

Select the MeshFrom the toggle menu (set to Initial by default), select one oftype of mesh to start the solution process:

Initial Mesh Select this to use the initial, coarse meshated at the start of the solution process. form an adaptive analysis if you select Inelements of an initial mesh are relativelytion that uses the initial mesh is not likelySeeding and lambda refinement can be mesh.

Current Mesh Select this to use the finite element mesrefined. To take advantage of a previousthis as the starting mesh. If no mesh hasCurrent Mesh is the same as selecting

Previous Mesh Select this to use the second to last refinrevert back to this mesh, choose Previomesh.If you plan to do a frequency sweep on aPrevious Mesh can save considerable psolution has converged based on the stoond to last mesh is almost as accurate athe S-matrix for each adaptive pass andparameters for the next to the last adaptMesh to use that smaller mesh.

Manual Select this if you have generated a manumaker.


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ptions.

mesh.

ow appears:

e following mesh types:

om the Meshmaker, you

anual refinement process. If for the problem, selecting itial mesh each time it starts.adaptive solution process. If e current mesh is the same

efore the most recently

reated.


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t Solutionaults

Mesh OptionsFrom the Mesh Options menu, choose one of the following o

Manual Mesh Choose Mesh Options/Manual Mesh to manually refine the

> To manually refine the mesh:1. Choose Mesh Options/Manual Mesh. The following wind

2. From the Select an existing mesh menu, select one of th

3. Choose Define Manual Mesh to enter the Meshmaker. Fr

Initial Selects the initial, coarse mesh to start the man adaptive solution has not been generatedInitial causes the Meshmaker to create an in

Current Selects the mesh most recently refined in the the mesh has not been adaptively refined, thas the initial mesh.

Previous Selects the finite element mesh created just brefined mesh.

Manual Selects the manual mesh you most recently c


may manually refine the mesh.

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FSS should refine the initial sh only apply when you are

w appears:

ed on the material-ment lengths are

based on seeding set up

ppears.ns.u return to the Initial


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t Solutionaults

Initial MeshChoose Mesh Options/Initial Mesh to specify how Ansoft Hmesh before solving. The refinement options for the initial meperforming an adaptive solution using the initial mesh.

> To specify the refinement options for the initial mesh:1. Choose Mesh Options/Initial Mesh. The following windo

2. Select Lambda Refinement to refine the initial mesh basdependent wavelength. This mesh is refined until most eleapproximately one-quarter wavelength.

3. Select Seed Based Refinement to seed the initial mesh in the Meshmaker. To define these operations:a. Choose Define Seed Operations. The Meshmaker ab. Use the Seed commands to define your seeding optioc. Save the seeding options and exit the Meshmaker. Yo

Mesh Refinement window.


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mesh.

ars next to Tetrahedra.

llowing guidelines to decide

ion passes to further refine

default.

olution based on the last olution.p after an adaptive solution between the last two

eed Based Refine- initial mesh.

meshes generated dur-ncy at which the adap-

for a frequency that akes sense to start with e new frequency.


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t Solutionaults

4. Choose OK to accept the refinement options for the initial

TetrahedraThe number of tetrahedra in the selected starting mesh appe

Deciding on a MeshIf you are generating the first solution for a project, use the fowhat type of mesh to use.

• In general, you should perform at least two adaptive solutthe mesh.

• Lambda refinement is recommended and is turned on by

Use the following guidelines for subsequent refinements.

• Use the current mesh whenever you want to generate a smesh that was created — or to further refine an existing s

• Use the previous mesh if you plan to do a frequency sweethat has converged, or where the change in S-parameterspasses is negligible.

Note: If you do not select either Lambda Refinement or Sment, Ansoft HFSS solutions begin with the coarse

Note: When starting with the current mesh, be aware thating an adaptive solution are optimized for the frequetive solution was generated. If a second solution is significantly differs from the adaptive frequency, it mthe initial mesh and adaptively refine the mesh at th


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lds.

patterns, impedances, and

ce for the latest solution. edance lines by choosing ecutive Commands menu.


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imum Frequencyimum Number of Eigen-desptiveptive Criteriaepting Meshve Selectionsllorts Onlypedance Only

missions Onlyt Solutionaults

Solve SelectionsFor a Driven Solution.

From the Solve area, select from the following options.

AllSelect All to generate a solution for all parameters and 3D fie

Ports OnlySelect Ports Only to quickly compute the excitation 2D field propagation constants at each port.

Impedance OnlySelect Impedance Only to re-compute only the port impedanThis would typically be used after you have redefined the impSetup Executive Parameters/Port Impedances from the Ex


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issions test.

ep was the last solution emissions test, Ansoft cy sweep information is olution at any frequency after a fast sweep has

te a unique full field range. Once the solution for that point is deleted next point. Because an

int, when you generate uency sweep, you must

tem generates a field at field solution and solv-herefore, select All to sweep or an interpolat-


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imum Frequencyimum Number of Eigen-desptiveptive Criteriaepting Meshve Selectionsllorts Onlypedance Only

missions Onlyt Solutionaults

Emissions OnlySelect Emissions Only to generate a solution only for the em

Note: Emissions Only is available if a fast frequency swegenerated. To calculate the maximum E-field for anHFSS uses the field solution. Because fast frequenstored in a file, Ansoft HFSS can generate the field spoint. An emissions test may be performed any timebeen generated without re-solving the problem.

Discrete and interpolating frequency sweeps generasolution for each division over the entire frequency is generated for a frequency point, the field solutionso that a new field solution can be generated for theemissions test requires the field solution at each poan emissions test with a discrete or interpolating freqsolve them both at the same time. This way the syssolution at a frequency point and, before deleting thing at the next point, performs the emissions test. Tperform an emissions test with a discrete frequencying sweep.


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pute the field solution and

olution for each port-mode wing from the options menu:

the field solution should be .

ons associated with all ional field solution — those increases the amount of tes, by default the system modes unless you specifi- the field solution, the asso-ource stimulation in the 3D

associated with the domi- option allows the system to ns associated with higher

ssociated with only a frac-ted. For example, if you set ort, specifying 2 instructs r all mode 1 and mode 2 ected, the Max Modes field


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imum Frequencyimum Number of Eigen-desptiveptive Criteriaepting Meshe Selectionst Solutionave Fieldsax Modesield Accuracyaults

Port SolutionIf the problem contains ports, specify on which modes to comthe accuracy of the field solution on the ports.

Save FieldsSpecify which field solutions to compute and save. The field scombination is saved in a separate file. Select one of the follo

Max ModesEnter the maximum number of modes at each port for which saved. This is only available when First N Modes is selected

All Modes Computes and saves the 3D field solutimodes at all ports. Because each additassociated with higher order modes — required disk space by several megabydoes not save the data for higher ordercally request it do so. If you do not saveciated mode will not be available as a sPost Processor.

Dominant Mode Computes and saves the field solutionsnant mode excitation at each port. Thissave disk space by deleting field solutioorder modes.

First N Modes Computes and saves the field solution ation of the modes that are being simulaup the model with four modes at each pthe system to save the field solutions foexcitations. When First N Modes is selis enabled.


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the finite element mesh on ified percent. Generally, the racy if:

impedances are computed

at are expected to be in the

ch time you request a ports- happens because a set of n process and then that set y a new Field Accuracy for project and then generate a

oing so gives you a set of curate adaptive solution.

ve solutions. Then, examine

refine the mesh for the stem uses the port field ull 3D solution. There-ult in an unnecessarily


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imum Frequencyimum Number of Eigen-desptiveptive Criteriaepting Meshe Selectionst Solutionave Fieldsax Modesield Accuracyaults

Field AccuracyThe Field Accuracy field tells the system to adaptively refineeach port until the error of the port solution is within the specdefault value is adequate. You may want improved port accu

• You are interested primarily in the port impedances. Port as part of the port solution.

• You need to lower the noise floor to catch S-parameters th−70 dB range.

> To specify a new value:• Enter the new value in the Field Accuracy field.

While the value entered in this field is used by the system eaonly solution, it is only used for the first full-field solution. Thisport solutions is computed at the beginning of the field solutiois used for all subsequent field solutions. Therefore, to specifa field solution, either delete the current solution or copy the new solution.

DefaultsChoose this button to reset all fields to their default values. Dsolution options that enables you to compute a reasonably ac

In general, use the suggested values for the first set of adaptithe convergence data to see if the solution has converged.

Note: Refining the mesh at the ports causes the system toentire structure as well. This occurs because the sysolutions as boundary conditions in computing the ffore, specifying too small a Field Accuracy can rescomplex finite element mesh.


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Topics: Ansoft HFSS — Setup Solution Setup Solutionread.pudn.com/downloads107/ebook/442805/hfss/solopt.pdf · Topics: Ansoft HFSS — Setup Solution Go Back Contents More Index