Welcome to CST !
CST STUDIO SUITE™ Training Class
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
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CST of America
CST Europe
CST China
CST of Korea
AET Japan
CST Products
CST MICROWAVE
Common Easy-To-Use Preand Post-processing Engine
STUDIO®
CST CABLE STUDIO™ CST PCB STUDIO™
Our Flagship Product for RF Simulations
CST MICROSTRIPES™
RF Simulations for Special Applications
CST STUDIO SUITE™
CST DESIGN STUDIO™ Circuit Simulator Allows Coupling of 3D Models
CST PARTICLE STUDIO® Interaction of EM Fields with Free Moving Charges 5
CST MPHYSICS STUDIO™ Thermal and Mechanical Effects of EM Fields
CST EM STUDIO® Simulations of Static or Low-Frequency Fields
Built-In Help Mechanisms
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Documentation
\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 9
Online Help (I)
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Online Help (II) - Links to Online Help -
In almost all dialogs there is a link to the online help documents which provides you with extensive help for all settings.
Linked page of the online help
Transient solver main dialog 11
CST Webpage
www.cst.com 12
CST Support Site Tutorial Videos
FAQ Section
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CST User Forum
Ask your questions. Answers are provided by other users or CST engineers. 14
CST Customer Support
CST Malaysia Phone: +60 (3) 7731 5595 Fax: +60 (3) 7722 5595 Email: [email protected] 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
CST PARTICLE STUDIO® Charged Particle Dynamics Training 1 full day
EMC / SI / PI Training
2 full days Performance Training 1 full day
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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
Basic and Advanced Modeling
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Common User Interface Menu Bar Tool Bars
Primary Window
Navigation Tree
Message Parameter List 20
Window
Customize Your Environment E.g., define a shortcut key to call your favorite macro.
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View Options “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.
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Primitives Cylinder
Torus
Cone
Sphere
Rotation
Brick
Elliptical
Hints:
Cylinder
Press the tab-key to enter a point numerically. Press backspace to delete a previously picked point.
Extrusion 23
Picks Pick a point, an edge, or a face in the structure.
Hints: Picked Edge
Picked Point
Pick circle center (c) Pick corner
Press "s" to activate all pick tools.
Picked Face
To pick a point by given coordinates, press “p” and the tab-key. 2nd time picking an element unselects it.
Pick face
Pick face (f)
center (a)
Clear picked elements (d)
point (p) Pick edge center (m) Pick point 24
on circle (r)
Edge from coordinates Pick edge (e)
Working Coordinate System 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.
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Working Coordinate System The WCS can be aligned, e.g., with a point, an edge, or a face. Align the WCS with a point
Align the WCS with an edge
Align the WCS with a face
Press “w” to align the WCS with the currently selected object. 26
Working Coordinate System The position of a WCS can be stored for later use.
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Boolean Operations Boolean operations can be applied to two or more shapes to create more complex structures. Sphere
Brick
Intersect Brick * Sphere 28
Add
Subtract
Brick + Sphere
Brick - Sphere
Boolean insert Sphere / Brick
Brick / Sphere
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 29
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.
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Specify rotation angle, material properties, etc. Double click on any corner point to change its position.
Analytical Modeling (I) 3D curves and faces can be created using analytical expressions.
Enter parameterization 33
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.
Pick two faces.
Choose the properties of the loft operation.
Preview
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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
Specify angle and width.
Select edges.
Specify radius.
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Shell Operation A solid object can be shelled. Example: A waveguide bend consisting of three shapes is shelled. solid2
solid3 solid1
Create a single shape by a Boolean add.
Picked faces will be open after the operation. 38
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. 40
Local Modifications – Remove Feature
Feature to be removed
Remove the feature 41
Pick the feature
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.
Paste the objects in the new WCS.
Press ctrl+c to copy objects to clipboard.
Move the WCS. 44
Align Objects Copied or imported objects can be aligned with the current model.
Select shape and choose “Align…”
Select faces to align with.
Choose angle.
Final Result
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.
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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. 46
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. 50
Transient Simulation - Behind the Scenes Output Time Signal
Excitation Time Signal
Numerical time integration of 3D Maxwell equations
Port 1
Port 2
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) 51
Frequency Domain Simulation – Behind the Scenes The steady state behavior of a model is calculated at different frequency points.
For each frequency point a linear equation system has to be solved.
The intermediate points in broadband results are calculated by an interpolation. 52
Time Domain + Frequency Domain in out
in out Time Domain
Frequency Domain Calculation
in
in
out
out
TDR 53
Frequency Domain
S-parameter
S-parameter
Solver Choice (I) - Overview General Purpose Solver (3D-Volume) Solver Transient
Frequency Domain
Area of Application (Rule of Thumb) Electrically medium and large sized problems Broadband Arbitrary time signals Narrow band / Single frequency Electrically small to medium sized problems Periodic structures with Floquet port modes
Special Solver (3D-Volume): Closed Resonant Structures Eigenmode FD Resonant
Strongly resonant structures, narrow band (e.g. cavities) Strongly resonant, non radiating structures (e.g. filters)
Special Solver (3D-Surface): Large Open Metallic Structures
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Integral Equation (based on MLFMM)
Electrically large structures Dominated by metal
Asymptotic Solver
RCS calculations for electrically very large objects
Solver Choice (II) - Resonances The following rules of thumb apply: Weak Resonances
Strong Resonances
General Purpose +AR-Filter for S-parameter calculation only
Resonant Fast
F-solver is better suited to strongly resonant applications than T-solver. 55
Solver Choice (III) - Electrical Size The following rules of thumb apply:
Structure under study
Electrically Small
Electrically Large
With MPI also very large problems can be solved.
RCS calculations for electrically very large structures
For electrically very small structures the quasistatic solvers provided in CST EM STUDIO® might be a good choice. 56
Solver Choice (IV) - Bandwidth The following rules of thumb apply: Narrowband
Broadband
F-solver and I-solver are better suited to narrowband applications, while the T-solver is better suited to broadband applications. 57
Specialized Products In addition to the general purpose solvers of CST MICROWAVE STUDIO® CST offers solvers specialized to certain classes of applications.
CST PCB STUDIO™ Specialized solvers for the simulation of PCB boards. CST CABLE STUDIO™
CST MICROSTRIPES™ Efficient solvers based on the Transmission Line Matrix (TLM) method. Contains special algorithms for EMC analysis. 58
Specialized solvers for the simulation of complete cable harnesses for all kind of EMC investigations.
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 60
Single Patch
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Single Patch Design Frequency range: 3 – 8 GHz Port size:
±2*width in y-direction
Copper Substrate (Rogers RT 5880)
±5*height in z-direction
40mm
20mm
0.5mm
0.035mm
h = 0.787mm
7.5mm 20mm w = 2.38mm 40mm Copper groundplane, thickness = 0.035 mm 62
Construction (i) Choose template:
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Load materials:
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) Construct the feed line… Press Shift-Tab
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Select edge centre
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 doubleclicking it
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Construction (ix) Transform solid1 to make a copy
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Construction (x) Select component patch
Select component solid1
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
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Exploit symmetry plane
Simulation Define monitors (E-, H-, Farfield @ 5.25 GHz) Start transient solver
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Visualize Results Farfield result
E-field result 78
Parameter Sweep
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Parameter Sweep Results: S11
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Optimization of Single Patch Optimizer Parameters
Optimizer Goal
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Optimizer Results (iii)
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Farfield Efficiency
Before optimization: 84
Patch Array
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Combine Farfields (1)
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Phaseshift = -45° (1R)
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Phaseshift = 135° (2L)
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Combine Farfields (2) Transform component1 to make a copy
Combine ground and substrate components
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Combine Farfields (2) Construct second port and run transient simulation without symmetry.
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Combine Farfields (2)
1
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2
Farfield Results (L)
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Farfield Results (R)
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Feeding Network Design (DS) lg/4
lg/4 Z0
Z0/sqrt(2)
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DS – MWS co-simulation
3D MWS model fed with DS circuit network
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Definition of Ports
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Available Port Types Ports for S-Parameter Computation
Discrete Ports
Waveguide Ports
(Lumped Element)
(2D Eigenmode Solver)
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). 99
Waveguide ports provide a better match to the mode pattern as well as higher accuracy for the S-parameters.
Discrete Ports S-Parameter Port
Current Port
Voltage Port
Voltage or current source with internal resistance
Coaxial
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Microstrip
Stripline
Coplanar waveguide
Discrete Edge Port Definition
Pick two points,
or
pick one point and a face,
or enter coordinates directly (not recommended).
Select port type and impedance.
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Discrete Face Port Definition
Pick two edges
Select port type and impedance.
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or
one edge and a face.
Available Port Types Ports for S-Parameter Computation
Discrete Ports
Waveguide Ports
(Lumped Element)
(2D Eigenmode Solver)
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). 103
Waveguide ports provide a better match to the mode pattern as well as higher accuracy for the S-parameters.
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.
Port backed with PEC solid.
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Extrude the port plane.
Materials & Boundary Conditions
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Basic Materials Define a new material or load materials from the large material database.
Material Types PEC = Perfect Electrical Conductor (
)
Normal: General material model. This is typically used for dielectric materials.
Anisotropic: Permittivity and permeability depend upon the spatial direction. Lossy Metal: Model for conductors with
Corrugated Wall: Surface impedance model.
Ohmic Sheet: Surface impedance model. 109
.
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 ymax
xmin zmin
zmax ymin xmax 112
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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Meshing Basics
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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). 120
Hierarchy of Mesh Settings Global Mesh Properties
General settings usually done by project template. Global settings for mesh controls of automatic meshing algorithms.
Local Mesh Properties
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 Select Project Template
Global Mesh Settings
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This adjusts the global mesh properties to values which we found to be a good starting point for a certain area of application.
Optimize the global mesh settings for the geometry of your model.
Local 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.
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)
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Initial Mesh Settings
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.
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Automatic Mesh Refinement (II)
The results for different meshes during an adaptive mesh refinement are shown in the "Navigation Tree". 125
Hexahedral Meshing for Transient Simulations
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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
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Hexahedral Mesh (I) - Mesh View Mesh lines in one mesh plane are shown in the 3D view. View mesh. Mesh controls are displayed in the mesh view.
Information about mesh plane.
The total number of mesh cells is displayed in status bar. 128
Corner Correction
Fixpoints
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.
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Automatically create and use mesh controls. Strongly recommended!
Hexahedral Mesh (III) - Global Settings Largest Mesh Step - "Lines per Wavelength"
"Lines per wavelength" is based on the upper limit of the frequency range. 130
Thus, increasing the upper frequency limit usually leads to a finer mesh.
Hexahedral Mesh (IV) - Global Settings Largest Mesh Step - "Lower Mesh Limit"
"Lower Mesh Limit" is based on the dimensions of the computational domain.
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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
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 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
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. 132
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. 133
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
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Representative Meshes (I) - Minimal Requirements 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.
Coaxial Line 1-2 mesh lines
2-3 mesh lines (depends on thickness)
Microstrip Line 135
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.
Representative Meshes (II) - Minimal Requirements The gap between multiple strip lines should be resolved by at least one or two mesh cells.
Parallel Microstrip Lines A discrete port must be discretized by at least one mesh cell.
Discrete Ports 136
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.
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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.
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Example: Staircase cell at a wire in free space.
Online Help - PBA and TST
PBA
139
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.
Hexahedral Meshing - Overview 1. Hexahedral Mesh Configuration Options 2. Some Meshing Guidelines 2.1 Some Representative Meshes for Common Structures 2.1 Meshing Pitfalls 3. Influence of the Mesh on Simulation Performance
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Hexahedral Meshing – Performance (I) 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.
Smallest Mesh Step
tiny t: slow
t
big t: fast
t
The smaller the smallest mesh step width, the smaller the time step for the numerical time integration. 141
Hexahedral Meshing – Performance (II) The smallest mesh step in a model can be visualized in the mesh view.
142
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.
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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”)
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Tetrahedral and Surface Meshing for Frequency Domain Simulations
145
Global Mesh Properties 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...) 146
Tetrahedral / Surface Mesh (I) -Global Mesh Settings -
"Steps per wavelength" is based on the upper limit of the frequency range. 147
Thus, increasing the upper frequency limit usually leads to a finer mesh.
Tetrahedral / Surface Mesh (II) -Global Mesh Settings -
"Min. number of steps" allows to refine the mesh globally independently of the frequency range settings.
148
It specifies the minimum number of mesh edges to be used for the diagonal of the model bounding box.
Mesh Generation Method The method for surface and volume meshing can be chosen. 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. Delaunay: Fast tetrahedral volume meshing method (recommended).
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. 149
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.
Curvature Refinement (I)
30
100
default = 100 If cylinders are still not well discretized, increase it to, e.g., 200-300.
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Curvature Refinement (II)
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.
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. 151
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 152
Optimized mesh
Open Discussion
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