Getting Started / Tutorials

Transcription

1 High-performance EM simulation software Technological leadership since 1992 Complete Technology for 3D EM 260 employees Worldwide support network Getting Started / Tutorials 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. 1

2 Tutorials Step-by-Step tutorials are available for CST MICROWAVE STUDIO and CST EM STUDIO. Examples Overview Many pre-calculated examples are available. Antenna Calculation Examples 2

3 Online Help Online help documents can be accessed in the "Help" section. It contains: - Highlights and New Features - Tutorials and Examples - Complete Documentation of all Features, Dialogs, VBA Language, etc. 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 3

4 Online Help You can find detailed explanations for many warnings and error messages in the online help. Just click on the link in the message window. Quick Start Guide File Options Preferences Open Quick Start Guide The Quick Start Guide helps new users to make all settings necessary to run a simulation model. Most of the settings are applied automatically by the project templates. 4

5 Cylindrical Horn Antenna (8 12 GHz) units: inch waveguide: 1.0 in x 0.5 in x 0.5 in aperture radius: 1.0 in, length: 0.25 in shell thickness: 0.01 in (outside) monitors: E-field, H-field & far field at 10 GHz New Projects - Project Templates Project templates are the preferred way to customize CST STUDIO SUITE automatically for a certain type of application. Your already defined project templates are listed in the section "Project Templates". If you haven't defined a project template for your application click on "Create a new project" to create one. 5

6 New Project Template - Horn At the beginning, choose "Create Project" to create a new project. This starts the configuration wizard in order to help you to choose the appropriate module, main project settings and result recorders for the particular application. We choose Microwave & RF Antennas Waveguide (Horn, Cone, etc.) The recommended solvers for the selected workflow are T, I and F. We choose the Time Domain solver. Change the dimensions to inch. New Project Template - Horn Apply Frequency settings and set 3D field monitors. 6

7 New Project Template Summary Horn Finally, verify your settings for the template and save it. Save the file as Horn_antenna.cst. Common User Interface Ribbon Bar Primary Window Navigation Tree Parameter List Message Window 7

8 Primitives Cylinder Cone Torus Sphere Brick Rotation Elliptical Cylinder Extrusion Hints: Press the tab-key to enter a point numerically. Press backspace to delete a previously picked point. 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 structure shift+spacebar zoom into selected shape mouse wheel dynamic zoom to mouse pointer. Default views are available in a drop down menu. Top view Views can be saved and restored. Perspective 8

9 Picks - Basic Pick a point, an edge or a face in the structure. Coordinates of picked point are shown in 3D view. Picked Point or S Edge length is shown in 3D view. Pick corner point, edge or face (s) Picked Edge Picked Face Hints: Press "s" to activate all pick tools. To pick a point by given coordinates, press "p" and the tab-key. Picking an element twice unselects it. Coordinate System The working coordinate system (WCS) allows the use of context dependent coordinates. Use to switch on/off the WCS. Use to rotate and move the WCS. 9

10 Coordinate System Alternatively, use and the left mouse button to rotate and move the WCS. Translation. Drag the axis of the principal coordinate. Rotation. Drag the ring segment around the principal axis. Multiple transforms can be performed by clicking "Apply" (or pressing Return ) between the single steps. 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. 10

11 Boolean Boolean operations can be applied to two or more shapes to create more complex structures. Sphere Brick Add Brick + Sphere Subtract Brick - Sphere Intersect Brick * Sphere Sphere / Brick Boolean insert Brick / Sphere Horn Antenna Construction (I) Define a brick (1.0 x 0.5 x 0.5 in) made of PEC. Pick face. Align the WCS with the face. Define a cylinder (outer radius: 1.0 in, height: 0.25 in) made of PEC. Move the WCS by 2.0 in. 11

12 Horn Antenna Construction (II) Pick two opposite faces. Perform a loft. Horn Antenna Construction (III) Select multiple objects (ctrl or shift + left mouse button). Perform a Boolean add. Shell solid: 0.01 in (outside). Pick two outer faces. 12

13 Definition of Ports Available Port Types Ports for S-Parameter Computation Discrete Ports (Lumped Elements) Waveguide Ports (2D Eigenmodes) Input: Knowledge of TEM Mode and line impedance is required. Output: Voltage and current Discrete ports can be used for TEMlike modes (cutoff frequency = 0), not for higher order modes. Input: Area for eigenmode solution Output: Pattern of E- and H-field, line impedance, propagation constant Waveguide ports provide a better match to the mode pattern as well as higher accuracy for the S-parameters. 13

14 Discrete Ports S-Parameter Port Current Port Voltage Port Current source with internal resistance. Realizes input power of 1W (peak). Wires 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. 14

15 Discrete Face Port Definition Pick two edges or one edge and a face. Select port type and impedance. Port Definition 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. 15

16 Port Definition Open Structures 1. Pick face. 2. Enter port menu. 3. Adjust additional port space using k and h. The extension factor k varies in a range of 5 10, typically depending on the ratio w/h, ε r and the frequency. Horn Antenna Port Definition Pick point inside corner. Define a waveguide port. Pick edge. Define the port on the internal profile. 16

17 Boundary Conditions and Symmetry Planes EM boundaries are defined by the chosen antenna template. Image theorem can be applied using symmetry planes to reduce the overall size of the calculation domain, thus speeding-up the simulation. Meshing Overview 17

18 How to Get a Good Mesh? 1. Use Project Templates For several classes of applications (e.g. antennas, PCB boards, etc.) there are some common properties for a "good" mesh. Project templates apply some basic settings for the particular area of application, including global mesh settings. 2. Use Automatic Default Settings Make use of automatic settings to let the software choose the most appropriate algorithm (e.g. order of curved elements). 3. Use Adaptive Mesh Refinement Typically the most efficient way to get a refined mesh is using the automatic mesh refinement which refines the initial mesh wherever needed according to solver error estimators. Mesh Generation - A Typical Workflow Project Template This adjusts the global mesh properties to values which we found to be a good starting point for a certain area of application. Global Mesh Settings Optimize the global mesh settings for the geometry of your model. Automatic Refinement Mesh Groups Perform Simulation Start the solver and perform a convergence study (e.g. using adaptive mesh refinement). yes no Automation Results Simulations and mesh studies provide insight about the dependency of the results on the mesh settings. 18

19 Mesh View View mesh. Mesh lines in one mesh plane are shown in the 3D view. Mesh controls are displayed in the mesh view. Information about mesh plane. The total number of mesh cells is also displayed in the status bar. Corner Correction Snap lines Global Settings (I) Absolute and frequency dependent settings to determine the largest mesh step. Settings to limit the size of the smallest mesh step. 19

20 Global Settings (II) Cells per wavelength" is based on the upper limit of the frequency range. Thus, increasing the upper frequency limit usually leads to a finer mesh. Cells per max model box edge" is based on the dimensions of the computational domain. The maximum cell size is calculated by dividing the largest edge of the model bounding box by this number. Global Settings (III) Maximum mesh cell size: Refinement in an area filled by the structure is possible in global mesh settings (previously only via local mesh properties). The structure bounding box defines refinement area. 20

21 Global Settings (IV) Minimum mesh cell size: Absolute or relative values are possible. Fraction of maximum cell Absolute value Mesh Groups Local mesh settings can be applied to single objects by defining a mesh group and assigning the object to the specific group, e.g. per drag&drop. The maximum mesh step width can be defined for each coordinate direction in a mesh group. Pre-defined groups are available for "Excluding from Simulation" and "Excluding from Bounding Box". Solid1 is ignored in the simulation but considered for the mesh. Only the sphere is considered for bounding box creation. 21

22 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). Often such cells do not influence the simulation result much, but if they introduce shortcuts this might be critical. Mesh View Mesh properties TST at work! Global mesh settings are defined by the chosen antenna template. 22

23 Transient Solver: Start Simulation The accuracy defines the steady-state monitor. The simulation is finished when the electromagnetic energy in the computational domain falls below this level. Analyze 1D Results Port signals S-parameters Power\Excitation [1] Energy Specific extra 1D Results are directly calculated due to the chosen project template. 23

24 Analyze 2D/3D Results Port information: cut-off frequency line impedance propagation constant Electric Field at 10 GHz 24

25 Farfield at 10 GHz Different Plot type can be chosen from the Farfield Plot ribbon. The Linear Directional polarization is plotted in 3D using the Ludwig 3 coordinate system. The orientation of the E field vector and the propagation directions are indicated in the plot. Polar Plot for Farfield at 10 GHz The Polar plot is obtained for E and H plane by selecting different Cut Angles. Phi=0 Phi=90 25

26 Comparing Polar plots The polar plots can be compared for different cut planes by copying them as 1D results using Farfield Plot properties. Tips & Tricks for an Accurate Farfield Tip 1: Choose sufficient accuracy. The accuracy level in the T-solver should be -40 db. For larger frequency bands (e.g. 0-3 GHz) or bad radiation it is better to use -60 db so that the E- and H-fields on the bounding box do not suffer from FFT/DFT truncation errors. 26

27 Tips & Tricks for an Accurate Farfield Tip 2: Set appropriate boundary conditions. The open (add space) boundary condition ensures λ/4 space at the center frequency. For lower frequencies (bigger λ) the space needs to be increased accordingly. Tips & Tricks for an Accurate Farfield Tip 3: Check the energy balance. At 4.5 GHz the farfield may be inaccurate. Farfield values become inaccurate, if S-parameter balance 1 (no power is radiated). In this case directivity and gain are calculated from dividing 0/0, which is numerically critical. A good measure for total radiated power is: (1 - balance). 27

28 Parameterization (I) 2*r1 Change outer radius value to variable r1. Parameterization (II) Outer diameter 2*r1 Select solid, then right-click and select Properties. 28

29 Result Processing Templates (Shift+P) Farfield and Antenna Properties Define gain(theta) at phi=0. Postprocessing templates provide a convenient way to calculate derived quantities from simulation results. Each template is evaluated for each solver run. Result Processing Templates (Shift+P) General 1D Define max. of gain (theta) Read the online help to learn more about the postprocessing in CST MWS. 29

30 Parameter Sweep - Settings Define a new parameter sweep. Sequence from 1 to 1.5 with 3 samples for the parameter r Parameter Sweep - Settings The 1D Results (e.g. S-Parameters) will be stored parametrically. The Result Templates will be returned in the Tables folder. 30

31 Parametric 1D Plot Parameter Sweep - Table Results 31