Cst training core module - antenna - (2)

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CST STUDIO SUITE™
Training Class
Welcome to CST !
Core Module

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About CST
 Founded in 1992
 170 employees
 World-wide distribution network
 Focus on 3D EM simulation

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

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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™
RFSimulations
forSpecial
Applications
CST MPHYSICS STUDIO™
Thermal and Mechanical
Effects of EM Fields
CST DESIGN STUDIO™
Circuit Simulator
Allows Coupling of 3D Models

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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.

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Tutorials
Step-by-Step tutorials are available for CST MICROWAVE STUDIO®
and CST EM STUDIO®.

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Examples Overview
Many pre-calculated examples are available.
Antenna Calculation Examples

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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 Support Site
FAQ Section
Tutorial Videos

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

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CST Customer Support
CST Malaysia
Phone: +60 (3) 7731 5595
Fax: +60 (3) 7722 5595
Email: info@sea.cst.com
Support available from
9am – 5pm

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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

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Basic and Advanced
Modeling

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Common User Interface
Navigation
Tree
Menu Bar
Tool Bars
Primary
Window
Parameter List
Message
Window

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Customize Your Environment
E.g., define a shortcut key
to call your favorite macro.

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 “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

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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

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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.

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Boolean Operations
Sphere
Brick
Add
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

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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

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

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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.

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Blend and Chamfer Edges
Select edges.
Specify angle and width.
Specify radius.

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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

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View Options
 Several options are available to gain better insight into the structure.
Cutting Plane
Wireframe Mode

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View Options
 Several options are available to gain better insight into the structure.
Working Plane
Coordinate Axes

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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.

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 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

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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.

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Solver Overview
Which 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.

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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)

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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
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
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

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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:

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Construction (ii)
Construct the substrate:
Load substrate material

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Construction (iii)
Construct the patch:

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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…

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Construction (viii)
Pick two points to form a
translation vector
Select solid1 by double-
clicking it

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Construction (ix)
Transform solid1 to make a copy

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Construction (x)
Select component solid1
Select 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

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Construct Port
Pick face of feed line

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Construct Port
Construct waveguide port

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Simulation Settings
Set freq. range Exploit symmetry plane

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Simulation
Define monitors (E-, H-, Farfield @ 5.25 GHz)
Start transient solver

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Visualize Results
Farfield result
E-field result

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Parameter Sweep Results: S11

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Optimization of Single Patch
Optimizer Parameters
Optimizer Goal

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Farfield Efficiency
Before optimization:

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Transform component1 to make
a copy
Combine ground and
substrate components
Combine Farfields (2)

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Combine Farfields (2)
Construct second port and run transient simulation
without symmetry.

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Feeding Network Design (DS)
Z0/sqrt(2)
Z0
lg/4
lg/4

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DS – MWS co-simulation
3D MWS model fed with
DS circuit network

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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.

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Discrete Ports
S-Parameter Port
Voltage or current source with
internal resistance
Current Port Voltage Port
Coaxial Microstrip Stripline Coplanar waveguide

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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.

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Discrete Face Port Definition
Pick two edges one edge and a face.or
Select port type
and impedance.

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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.

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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.

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Port Definition (II) – Open Structures
1. Pick three points.
2. Enter port menu .
3. Adjust additional
port space.

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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.

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Materials
&
Boundary Conditions

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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

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Material Database
Loaded materials are available
for the creation of new shapes.

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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.

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Boundaries
CST 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

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Boundary Settings (I)
Seven different settings are available.

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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).

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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 .

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Boundaries: Symmetry Planes
Three different settings are available.
Three possible symmetry planes.

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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).

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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.

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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).
Results
Simulations 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

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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".

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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 Settings
Largest 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 Settings
Largest 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 Settings
Smallest 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 Settings
Smallest 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 Method
The 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

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