CST Training Core Module

1

CST STUDIO SUITE™

Training Class

Welcome to CST !

Core Module

3

About CST

Founded in 1992

170 employees

World-wide distribution network

Focus on 3D EM simulation

4

CST Worldwide

CST West Coast CST of America CST Europe CST China CST of Korea AET Japan

5

CST Products

CST MICROWAVE STUDIO®

Our Flagship Product

for RF Simulations

CST EM STUDIO®

Simulations of Static or

Low-Frequency Fields

CST PARTICLE STUDIO®

Interaction of EM Fields with

Free Moving Charges

CST STUDIO SUITE™ Common Easy-To-Use Pre-

and Post-processing Engine

CST CABLE STUDIO™

CST PCB STUDIO™

CST MICROSTRIPES™

RF S

imula

tions

for

Specia

l

Applicati

ons

CST MPHYSICS STUDIO™

Thermal and Mechanical

Effects of EM Fields

CST DESIGN STUDIO™

Circuit Simulator

Allows Coupling of 3D Models

6

Built-In Help

Mechanisms

7

Documentation<CST_INSTALLATION_DIR>\Documentation\

The introductory books are a good starting

point to learn the workflow of the CST

STUDIO SUITE™ products.

All books are available as pdf documents

in the "Documentation" subfolder of your

CST installation.

8

TutorialsStep-by-Step tutorials are available for CST MICROWAVE STUDIO®

and CST EM STUDIO®.

9

Examples OverviewMany pre-calculated examples are available.

Antenna Calculation Examples

10

Online Help (I)

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Online Help (II)

In almost all dialogs there is a link to the online help documents

which provides you with extensive help for all settings.

Transient solver main dialog

Linked page of the online help

- Links to Online Help -

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CST Webpage

www.cst.com

13

CST Support Site

FAQ Section

Tutorial Videos

14

CST User Forum

Ask your questions. Answers are provided by other users or CST engineers.

15

CST Customer Support

CST Malaysia

Phone: +60 (3) 7731 5595

Fax: +60 (3) 7722 5595

Email: [email protected]

Support available from

9am – 5pm

mailto:[email protected]

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CST Training Courses

The training courses for CST STUDIO SUITE™ provide you with the

knowledge needed for an efficient start with the software.

Currently the following trainings are offered on a regular basis. All

upcoming courses are announced on the CST webpage.

CST STUDIO SUITE™

MW & Antenna Training

2 full days

EMC / SI / PI Training

2 full days

Performance Training

1 full day

CST PARTICLE STUDIO®

Charged Particle

Dynamics Training

1 full day

CST EM STUDIO®

LF Applications Training

1 full day

CST MICROSTRIPES™

CST MICROSTRIPES™

Training

1-2 full day(s)

CST CABLE STUDIO™

CST PCB STUDIO™

Training on Demand

19

Basic and Advanced

Modeling

20

Common User Interface

Navigation

Tree

Menu Bar

Tool Bars

Primary

Window

Parameter List

Message

Window

21

Customize Your Environment

E.g., define a shortcut key

to call your favorite macro.

22

“Rectangle zoom” allows to zoom in a rectangular domain.

Change the view by dragging the mouse while pressing the left

button and a key.

ctrl - rotation

shift - in-plane rotation

ctrl+shift - panning

Some other useful options are:

spacebar - reset view to structure,

ctrl+f - reset view,

shift+spacebar - zoom into selected shape,

mouse wheel - dynamic zoom to mouse pointer.

View Options

23

Primitives

Cone Torus

Rotation

Cylinder

Sphere

Brick

Elliptical

Cylinder

Extrusion

Hints:

Press the tab-key to enter

a point numerically.

Press backspace to delete

a previously picked point.

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Pick corner

point (p)

Pick edge

center (m)

Pick circle

center (c)

Pick point

on circle (r)

Pick face

center (a)

Pick edge (e)

Pick face (f)

Clear picked elements (d)

Edge from

coordinates

Picks

Pick a point, an edge, or a face in the structure.

Hints:

Press "s" to activate all pick tools.

To pick a point by given coordi-

nates, press “p” and the tab-key.

2nd time picking an element

unselects it.

Picked Point Picked Edge Picked Face

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The working coordinate system (WCS) allows the use of context

dependent coordinates.

Use to switch on/off the WCS.

Use to rotate the WCS.

Use to move the WCS.

Working Coordinate System

26


Align the WCS

with a point

Align the WCS

with an edge

Align the WCS

with a face

The WCS can be aligned, e.g., with a point, an edge, or a face.

Press “w” to align the WCS with the currently selected object.

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The position of a WCS can be stored for later use.

28

Boolean Operations

Sphere

BrickAdd

Brick + Sphere

Subtract

Brick - Sphere

Intersect

Brick * Sphere

Boolean insert

Sphere / Brick Brick / Sphere

Boolean operations can be applied to two or more shapes to

create more complex structures.

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Curve Modeling Tools – Overview (I)

Curves can be used for

structure generation,

thin wire generation,

integration path in post-processing,

healing CAD data.

Basic Curves

Generation

Create new curve

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Curve Modeling Tools – Overview (II)

Solids can be created from curves.

Creation of a

Sheet from a

Planar Curve

Extrusion of a

Planar Curve

Sweep Curve

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Curve Modeling Tools – Overview (III)

Solids can be created from curves.

Creation of a

Trace

Creation of

Loft from two

Curves

32

Rotation of Profile

Rotation Axis

Draw the profile.

Press backspace to delete

the last selected point.

Specify rotation angle,

material properties, etc.

Double click on any corner

point to change its position.

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Analytical Modeling (I) 3D curves and faces can be created using analytical expressions.

Enter parameterization

34

Analytical Modeling (II) 3D curves and faces can be created using analytical expressions.

35

Loft Operation Two picked faces can be used to create a new shape by a loft

operation.

Choose the properties

of the loft operation.

Preview

Pick two faces.

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Bending It is possible to bend a sheet on a solid object.

Example:

Creation of a Helix

Sheet

Solid

The solid and the sheet must touch each other.

37

Blend and Chamfer Edges

Select edges.

Specify angle and width.

Specify radius.

38

Shell Operation A solid object can be shelled.

Example:

A waveguide bend consisting of three shapes is shelled.

solid1

solid3

solid2

Create a single shape

by a Boolean add.

Picked faces will be open

after the operation.

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Transform Operation Existing objects can be translated, rotated, mirrored, and scaled.

Translate Scale Rotate

Use the mouse to translate, rotate, or scale objects interactively.

Perform several transformations to the same shape using the “Apply”

button.

Selecting more than one solid will turn the shape center into the

common center.

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Local Modifications – Face Modifications

Offset Face: Interactively

move the face of a solid in

its normal direction.

Move Face: Interactively

move the face of a solid in

a coordinate direction.

Local Modifications are especially helpful

when you are working with an imported

CAD model for which the model history is

not available. The "Local Modification"

tools help you to modify such geometries.

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Local Modifications – Remove Feature

Feature to be removed Pick the feature

Remove the feature

42

View Options

Several options are available to gain better insight into the structure.

Cutting Plane

Wireframe Mode

43

View Options

Several options are available to gain better insight into the structure.

Working Plane

Coordinate Axes

44

Copy / Paste Structure Parts

Ctrl+C stores the selected solids on the active working coordinate

system (WCS) to the clipboard. Ctrl+V pastes the clipboard into the

active working coordinate system.

Copy and paste of structure parts works even between different CST

projects.

Press ctrl+c to copy

objects to clipboard.

Move the WCS.

Paste the objects in

the new WCS.

45

Copied or imported objects can be aligned with the current model.

For copied and imported objects, the alignment is started

automatically.

For shapes selected in the “Navigation Tree” start by choosing “Align…”

from the “Objects” menu.

Align Objects

Select shape and

choose “Align…”

Select faces to

align with.

Choose angle. Final Result

46

Interactive CAD Modeling Using the Mouse

1. Adjust the “Snap width” according to the raster of your structure.

2. Use the pick tools, whenever geometrical information is already available.

• Pick points to define new shapes / height of extrusion / transform.

• Pick edges for rotation axis / to adjust WCS.

• Pick face for extrude / rotate / transform / to adjust WCS.

3. Use the local working coordinate system (WCS).

4. Use the keyboard only for new (independent) geometric information

(e.g. points which cannot be picked and do not fit into the snapping raster).

Relative construction via picks and WCS avoids redundant information.

Parameters/Values are entered once and are later referenced via picks.

49

Solver OverviewWhich solver is best suited to my application?

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Which Solver is the “Best”?

Unique answer to this question is not easily possible as the

performance and accuracy depend on many parameters:

• Electrical size and geometry of the problem,

• Material models and material parameters used,

• Resonant behavior of the model,

• Type of the mesh and the boundary conditions,

• Architecture of the workstation used for the simulation,

• etc.

BUT: Some helpful rules of thumb are available.

The application engineers of CST are available to

discuss the solver choice and the model setup.

51

Transient Simulation - Behind the Scenes

Port 1 Port 2

Excitation Time Signal Output Time Signal

Numerical time integration

of 3D Maxwell equations

The simulation duration depends on:

1. Duration of input signal (determined by frequency range selected)

2. Duration of output signal (determined mainly by the size and the

resonances of the model under study)

3. Time step width for numerical time integration (determined by the

mesh used to discretize your model)

52

Frequency Domain Simulation –

Behind the Scenes The steady state behavior of a model is calculated at different

frequency points.

The intermediate points in broadband results are calculated by an

interpolation.

For each frequency

point a linear

equation system

has to be solved.

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Time Domain + Frequency Domain

Frequency DomainTime Domain

in

out

TDR S-parameter S-parameter

Frequency Domain Calculation

in

out

outin outin

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Solver Choice (I) - Overview

Transient

Electrically medium and large sized problems

Broadband

Arbitrary time signals

Frequency

Domain

Narrow band / Single frequency

Electrically small to medium sized problems

Periodic structures with Floquet port modes

Special Solver (3D-Volume): Closed Resonant Structures

Eigenmode Strongly resonant structures, narrow band (e.g. cavities)

FD Resonant Strongly resonant, non radiating structures (e.g. filters)

Special Solver (3D-Surface): Large Open Metallic Structures

Integral Equation

(based on MLFMM)

Electrically large structures

Dominated by metal

Asymptotic Solver RCS calculations for electrically very large objects

General Purpose Solver (3D-Volume)

Area of Application (Rule of Thumb)Solver

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Solver Choice (II) - Resonances

Weak Resonances Strong Resonances

+AR-Filter

for S-parameter

calculation only

Resonant Fast

The following rules of thumb apply:

General Purpose

F-solver is better suited to strongly resonant applications than T-solver.

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Solver Choice (III) - Electrical Size

Electrically Small Electrically Large

The following rules of thumb apply:Structure under study

For electrically very small structures the quasistatic solvers provided in

CST EM STUDIO® might be a good choice.

With MPI also very large

problems can be solved.

RCS calculations for electrically

very large structures

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Solver Choice (IV) - Bandwidth

The following rules of thumb apply:

BroadbandNarrowband

F-solver and I-solver are better suited to narrowband applications,

while the T-solver is better suited to broadband applications.

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Specialized Products In addition to the general purpose solvers of CST MICROWAVE STUDIO®

CST offers solvers specialized to certain classes of applications.

Specialized solvers for the

simulation of PCB boards.

CST PCB STUDIO™

CST CABLE STUDIO™

Specialized solvers for the

simulation of complete cable

harnesses for all kind of EMC

investigations.CST MICROSTRIPES™

Efficient solvers based on the

Transmission Line Matrix (TLM)

method. Contains special

algorithms for EMC analysis.

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Optional Workflow Example

Patch Antenna Array

Purpose 1: Design a single patch using

a parameter sweep & optimization.

Purpose 2: Create a dual patch array

using

a farfield array combination

3D array creation

a beam-forming feeding network

61

Single Patch

62

Single Patch Design

40mm

40mm

h = 0.787mm

20mm

20mm

0.035mm

Copper groundplane,

thickness = 0.035 mm

7.5mm

0.5mm

Substrate (Rogers RT 5880)

Copper

w = 2.38mm

Frequency range: 3 – 8 GHz

Port size:

±2*width in y-direction

±5*height in z-direction

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Construction (i)

Choose template: Load materials:

64

Construction (ii)

Construct the substrate:

Load substrate material

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Construction (iii)

Construct the patch:

66

Construction (iv)

Align WCS with picked

point

Select edge centre

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Construction (v)

Press Shift-Tab Select edge centre

Construct the feed line…

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Construction (vi)

Pick point

Align WCS with picked point

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Construction (vii)

Construct the feed

gaps…

70

Construction (viii)

Pick two points to form a

translation vector

Select solid1 by double-

clicking it

71

Construction (ix)

Transform solid1 to make a copy

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Construction (x)

Select component solid1Select component patch

Hit ENTER to substract

solid1 from patch

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Construction (xi)

Pick bottom face of

substrate

Extrude face to make

ground plane

74

Construct Port

Pick face of feed line

75

Construct Port

Construct waveguide port

76

Simulation Settings

Set freq. range Exploit symmetry plane

77

SimulationDefine monitors (E-, H-, Farfield @ 5.25 GHz)

Start transient solver

78

Visualize Results

Farfield result

E-field result

79

Parameter Sweep

80

Parameter Sweep Results: S11

81

Optimization of Single Patch

Optimizer Parameters

Optimizer Goal

83

Optimizer Results (iii)

84

Farfield Efficiency

Before optimization:

85

Patch Array

86

Combine Farfields (1)

87

Phaseshift = -45° (1R)

88

Phaseshift = 135° (2L)

89

Transform component1 to make

a copy

Combine ground and

substrate components


90


Construct second port and run transient simulation

without symmetry.

91


1 2

92

Farfield Results (L)

93

Farfield Results (R)

94

Feeding Network Design (DS)

Z0/sqrt(2)

Z0

lg/4

lg/4

95

DS – MWS co-simulation

3D MWS model fed with

DS circuit network

98

Definition of Ports

99

Ports for S-Parameter Computation

Discrete Ports

(Lumped Element)

Waveguide Ports

(2D Eigenmode Solver)

Available Port Types

Input: Knowledge of TEM Mode and

line impedance is required.

Output: Voltage and current

Input: Area for eigenmode solution

Output: Pattern of E- and H-field,

line impedance,

Propagation constant

Discrete ports can be used for TEM-like modes, not for higher order

modes (cutoff frequency > 0).

Waveguide ports provide a better match to the mode pattern as well

as higher accuracy for the S-parameters.

100

Discrete Ports

S-Parameter Port

Voltage or current source with

internal resistance

Current Port Voltage Port

Coaxial Microstrip Stripline Coplanar waveguide

101

Discrete Edge Port Definition

Pick two points, pick one point and a face,or

or enter coordinates directly (not recommended).

Select port type

and impedance.

102

Discrete Face Port Definition

Pick two edges one edge and a face.or

Select port type

and impedance.

103

Ports for S-Parameter Computation

Discrete Ports

(Lumped Element)

Waveguide Ports

(2D Eigenmode Solver)

Available Port Types

Input: Knowledge of TEM Mode and

line impedance is required.

Output: Voltage and current

Input: Area for eigenmode solution

Output: Pattern of E- and H-field,

line impedance,

propagation constant

Discrete ports can be used for TEM-like modes, not for higher order

modes (cutoff frequency > 0).

Waveguide ports provide a better match to the mode pattern as well

as higher accuracy for the S-parameters.

104

Port Definition (I) – Closed Structures

Typically, waveguide ports are defined based on a geometric object. Use the

pick tools to select a unique port plane.

The port size is equal to the smallest rectangular area which includes all picked objects.

105

Port Definition (II) – Open Structures

1. Pick three points.

2. Enter port menu .

3. Adjust additional

port space.

106

Port Definition (III) - Backing For the I-solver and the F-solver waveguide ports must be backed with

a PEC solid (or by electric boundaries).

Pick port using

the pick tools.

Extrude the port plane.

Port backed with PEC solid.

108

Materials

&

Boundary Conditions

109

Basic Materials

Normal: General material model. This is

typically used for dielectric materials.

Lossy Metal: Model for conductors with .

Anisotropic: Permittivity and permeability

depend upon the spatial direction.

PEC = Perfect Electrical Conductor ( )

Corrugated Wall: Surface impedance model.

Ohmic Sheet: Surface impedance model.

Define a new material or load materials from the large material database.

Material Types

110

Material Database

Loaded materials are available

for the creation of new shapes.

111

Lossy Metal

Why is it required?

Sampling of skin depth would require very fine mesh steps at

the metal surface when defining conductor as a normal material

(skin depth for copper at 1 GHz approx. 2 m).

This results in a very small time step, which leads to a very long

simulation time.

Solution:

1D model which takes skin depth into account without spatial

sampling.

112

BoundariesCST MWS uses a rectangular grid system, therefore, also the complete calculation

domain is of rectangular shape 6 boundary surfaces have to be defined at the

minimum and maximum position in each coordinate direction (xmin, xmax, ymin,

ymax, zmin, zmax).

Example: T-Splitter

xmin

xmax

ymin

ymax

zmin

zmax

113

Boundary Settings (I)

Seven different settings are available.

114

Boundary Settings (II)

Electric Boundaries (default setting): No tangential electric field at surface.

Magnetic Boundaries: No tangential magnetic field at surface. Default

setting for waveguide port boundaries.

Open Boundaries: Operates like free space – Waves can pass this boundary

with minimal reflections. Perfectly matched layer (PML) condition.

Open (add space) Boundaries: Same as open, but adds some extra space for

far field calculation (automatically adapted to center frequency of desired

bandwidth). This option is recommended for antenna problems.

Conducting Wall: Electric conducting wall with finite conductivity (defined

in Siemens/meter).

115

Boundary Settings (III)

Periodic Boundaries: Connects two opposite boundaries where the calculation

domain is simulated to be periodically expanded in the corresponding direction.

Thus, it is necessary that facing boundaries are defined as periodic.

The resulting structure represents an infinitely expanded antenna pattern,

phased array antennas. F! (hexahedral mesh), T! + 0 phase shift

Unit Cell: Used with F! solver, tetrahedral mesh, similar to F! periodic

boundary with hexahedral mesh. A two dimensional periodicity other than

in direction of the coordinate axes can be defined. If there are open

boundaries perpendicular to the unit cell boundaries, they are realized by

Floquet modes, similar to modes of a waveguide port .

116

Boundaries: Symmetry Planes

Three different settings are available.

Three possible symmetry planes.

119

Meshing Basics

120

How to Get a Proper Mesh?

Question: How does a proper mesh look like and what are the

best settings to get it?

Answer: This depends on your problem under study as well as

the type of result you are interested in.

However, there are some rules of thumb:

• For several classes of application (e.g. antennas, PCB boards

etc.) there are some common properties a "good" mesh

possesses (project templates make use of this fact).

• It is known that the results become more accurate when the

mesh is refined (automatic mesh refinement is based on this

knowledge).

• Geometry and material of the model influences the behavior of

the EM fields (fixpoints, material based meshing, and other

special techniques are based on this knowledge).

121

Hierarchy of Mesh Settings

Global Mesh Properties

Local Mesh Properties

General settings usually done by project

template. Global settings for mesh controls of

automatic meshing algorithms.

Special settings (fine-tuning) to adjust the

global mesh better to the model under study.

Defined per shape or per material.

Local mesh properties have precedence over global mesh properties.

122

Mesh Generation - A Typical Workflow

This adjusts the global mesh properties to

values which we found to be a good starting

point for a certain area of application.

Select Project Template

Optimize the global mesh settings for the

geometry of your model.

Local Mesh Settings

Global Mesh Settings

Fine tune the mesh (if necessary) to meet the

really specific requirements of your model.

Perform Simulation Start the solver and perform a convergence

study (e.g. using adaptive mesh refinement).

ResultsSimulations and mesh studies provide insight

about the dependency of the results on the

mesh settings.

123

Project Templates A project template makes some basic settings for a new project. A

project template can be applied to an already existing project.

Information about the

settings the template

will apply.

Template Title

(Area of Application) Initial Mesh Settings

124

Automatic Mesh Refinement (I) It is known that the numerical solution calculated by the solvers converges to

the analytical solution if the grid is sufficiently refined.

The automatic mesh refinement in CST tries to refine the initial mesh in a

clever way such that the results are accurate.

125

Automatic Mesh Refinement (II)

The results for different meshes during an adaptive mesh

refinement are shown in the "Navigation Tree".

126

Hexahedral Meshing for

Transient Simulations

127

Hexahedral Meshing - Overview

1. Hexahedral Mesh Configuration Options

2. Some Meshing Guidelines

2.1 Some Representative Meshes for Common Structures

2.2 Meshing Pitfalls

3. Influence of the Mesh on Simulation Performance

128

Hexahedral Mesh (I) - Mesh View

View mesh.

Mesh lines in one

mesh plane are shown

in the 3D view.

Information about mesh plane.

Mesh controls are

displayed in the mesh

view.

Corner

Correction FixpointsThe total number of mesh

cells is displayed in status bar.

129

Hexahedral Mesh (II) - Global Settings

Absolute and frequency

dependent setting to

determine the largest

mesh step.

Settings to limit the

size of the smallest

mesh step.

Automatically create

and use mesh controls.

Strongly recommended!

130

Hexahedral Mesh (III) - Global SettingsLargest Mesh Step - "Lines per Wavelength"

"Lines per wavelength" is based on the

upper limit of the frequency range.

Thus, increasing the upper frequency limit

usually leads to a finer mesh.

131

Hexahedral Mesh (IV) - Global SettingsLargest Mesh Step - "Lower Mesh Limit"

"Lower Mesh Limit" is based on the

dimensions of the computational domain.

The diagonal of the smallest boundary

face of the comp. domain is divided by

this number. Result is used as the max.

mesh step width allowed in the model

132

Hexahedral Mesh (V) - Global SettingsSmallest Mesh Step - "Mesh Line Ratio Limit"

The time needed to complete a time domain simulation heavily depends on the size

of the smallest mesh step (see later in section "Performance Aspects of Meshing").

The "Mesh Line Ratio Limit" specifies the

maximum value allowed for the ratio of the

maximum mesh step width to the minimum

mesh step width.

The size of the minimum mesh step can be

limited using the "Mesh Line Ratio Limit" or the

"Smallest Mesh Step" setting.

Mesh lines are

inserted at

fixpoints.

Mesh Line Ratio Limit

133

Hexahedral Mesh (V) - Global SettingsSmallest Mesh Step - "Smallest Mesh Step"

The time needed to complete a time domain simulation heavily depends on the size

of the smallest mesh step (see later in section "Performance Aspects of Meshing").

Smallest Mesh Step

The "Smallest Mesh Step" specifies the minimum

value allowed for the minimum mesh step

width in terms of the units defined in your

project.

Note: If the settings for "Steps per Wavelength"

or "Lower Mesh Limit" lead to a smaller

then the "Smallest Mesh Step" setting is

ignored.

134







135

Representative Meshes (I) - Minimal Requirements

Coaxial Line

The gap between inner and outer conductor

should be resolved by at least one mesh cell.

Partially filled cells are handled with PBA/FPBA

technique.

Microstrip Line

Depending on the thickness and the

permittivity of the substrate the number

of mesh lines should be at least as shown

in the picture.

It is NOT necessary to resolve the

thickness of the microstrip line by the

mesh.

2-3 mesh lines

(depends on thickness)

1-2 mesh lines

136

Representative Meshes (II) - Minimal Requirements

Parallel Microstrip Lines

The gap between multiple strip lines should be

resolved by at least one or two mesh cells.

A discrete port must be discretized by at least

one mesh cell.

Discrete Ports

137

Meshing Pitfalls - Staircase Cells (I)

Cells which contain more than two metallic

material boundaries are completely filled

with PEC (staircase cells).

A warning is shown by the

solver to inform you of this

modification.

Staircase cells are shown in the

mesh view.

138

Meshing Pitfalls - Staircase Cells (II)

Staircase cells must be avoided if

they influence the electrical

behavior of the model, i.e. if they

introduce shortcuts.

Example: Shortcut between two

microstrip lines is introduced by a

staircase cell.

Staircase cells which do not change

the electrical behavior of a model

are usually OK.

Example: Staircase cell at

a wire in free space.

139

Online Help - PBA and TST

PBA TST

Whenever a mesh cell cuts more than two metallic material

boundaries the cell is filled with PEC material (staircase cell).

Quite often such cells do not influence the simulation result

much, but if they introduce shortcuts (as shown on the previous

slide) this might be critical.

140







141

Hexahedral Meshing – Performance (I)

t

tiny t: slow

For stability, the time step of the numerical quadrature is determined by the

smallest mesh step. Increasing the smallest mesh step will increase the

time step.

big t: fast

t

The smaller the smallest mesh step width, the smaller the time

step for the numerical time integration.

Smallest Mesh Step

142

The smallest mesh step in a model can be visualized in the mesh

view.

Hexahedral Meshing – Performance (II)

143

Hexahedral Meshing Guidelines - Summary

Select a proper project template for your application to get good

initial mesh settings.

Perform an adaptive mesh refinement to find a good mesh.

Fine tune the mesh if necessary using the local mesh settings.

Try to avoid critical cells. Quite often they are an indicator that the

mesh is too coarse at least in some regions.

Try to avoid to use a mesh with a very high mesh line ratio limit.

Consider using subgrids for models which require a very fine mesh at

localized positions.

144

Transient Simulation - Memory Consumption- Memory-Consumption versus Mesh Size -

Some “rules of thumb” are:

A structure with open boundaries and material losses requires

about 1 GB RAM to handle 3-4 million mesh cells.

A structure with closed boundaries and without material losses

requires about 1 GB RAM to handle 5 million mesh cells.

Subgridding:

The subgridding feature starts to be efficient when the “mesh

cell reduction factor” is larger than 3.

(“Macros” “Calculate” “Subgridding Meshcell Factor”)

145

Tetrahedral and Surface Meshing

for Frequency Domain Simulations

146

Steps per wavelength: This value refers to the

highest frequency of the simulation. It defines the

minimum number of mesh cells that are used for a

distance equal to this wavelength.

Minimum number of steps: This value controls the

global relative mesh size and defines a lower bound

for the number of mesh cells independently of the

wavelength. It specifies the minimum number of

mesh edges to be used for the diagonal of the model

bounding box.

Note: A tetrahedral mesh requires a valid ACIS model.

(HEX mesh even works with INVALID ACIS model...)

Global Mesh Properties

147

"Steps per wavelength" is based on the

upper limit of the frequency range.

Thus, increasing the upper frequency limit

usually leads to a finer mesh.

Tetrahedral / Surface Mesh (I) -Global Mesh Settings -

148

Tetrahedral / Surface Mesh (II) -Global Mesh Settings -

"Min. number of steps" allows to refine

the mesh globally independently of the

frequency range settings.

It specifies the minimum number of

mesh edges to be used for the diagonal

of the model bounding box.

149

Mesh Generation MethodThe method for surface and volume meshing can be chosen.

Geometry accuracy: If the defined

or imported geometry is less

accurate than the default tolerance

1e-6, it is recommended to select a

larger tolerance. Otherwise artificial

shapes might arise or the model

preparation might fail.

Delaunay: Fast tetrahedral volume meshing

method (recommended).

Advancing Front: An alternative method to

generate a volume mesh. Advantageous in some

cases (like thin layers), because the surface

mesh can be generated more flexible than with

Delaunay, that is, it can be altered during the

mesh generation if necessary. This method is

available only in combination with the general

purpose surface mesh generation.

General purpose: A simple surface mesh

generation which is adequate in most cases.

Fast (for complex structures): Especially suited

to meshing large or complex structures. If used

together with (tetrahedral) volume mesh

generation, this method can be combined only

with Delaunay volume mesh generation.

150

default = 100

If cylinders are

still not well

discretized,

increase it

to, e.g., 200-300.

Curvature Refinement (I)

30 100

151

Volume optimization: If this field is checked

(recommended), the mesh connectivity of the

preliminary volume mesh is changed to improve the

mesh quality.

Volume smoothing: If this field is checked

(recommended), the position of mesh vertices will

be changed in order to enhance the mesh quality.

The “Curvature refinement ratio” specifies the ratio of

the maximum deviation (d) of the surface mesh from the

actual shape of the structure divided by the edge length

(h) of the surface triangle (as shown in the picture above).

Smaller values lead to better approximation of curved

objects.

Curvature Refinement (II)

152

Adaptive Mesh Refinement

Multi-frequency adaptive mesh refinement

The adaptation frequency samples are sequentially processed before the broadband sweep.

Example: Diplexer

Mesh adaptation at 75.1 GHz and 77 GHz.

Initial mesh Optimized mesh

153

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