21.12.2009
Workflow Example Horn Antenna Purpose : Optimize the aperture of the horn antenna such that the gain is maximized at 10 GHz.
1
CST MWS - Standard Workflow Choose a project template. Create your model. parameters + geometry + materials
Define ports. Set the frequency range. Specify boundary and symmetry conditions. Define monitors. Check the mesh. Run the simulation. 2
1
21.12.2009
Cylindrical Horn Antenna 8 – 12 GHz 1 0.5 0.5 dia=2, rad=1
zlength=2 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
0.25
3
Project Template At the beginning choose
“File” -> “New”
For an existing project you may choose
to create a new project.
“File” -> “Select Template”.
The project templates customize the default settings for particular types of applications. 4
2
21.12.2009
Project Template background material
Antennas should be modeled with vacuum as background material.
PEC is very practical for closed structures. (e.g. waveguides, connectors, filters)
The project templates customize the default settings for particular types of applications. 5
Change the Units
Define units.
6
3
21.12.2009
Horn Antenna – Construction (I)
Define a brick (1.0 x 0.5 x 0.5 in) made of PEC.
Define a cylinder (outer radius: 1.0 in, height: 0.25 in) made of PEC. 7
Pick face. Align the WCS with the face.
Move the WCS by 2.0 inches.
Horn Antenna – Construction (II)
Pick two opposite faces.
Perform a loft.
8
4
21.12.2009
Horn Antenna – Construction (III) Perform a Boolean add. Select multiple objects (ctrl or shift + left mouse button).
shell solid: 0.01 in (outside)
Pick two faces.
9
Port Definition Pick point inside corner.
Define a waveguide port.
Pick edge.
Define the port on the internal profile. 10
5
21.12.2009
Set the Frequency Range
Set the frequency range.
11
Boundary Conditions and Symmetry Planes
12
6
21.12.2009
3D Monitors
Add field monitors for E-field, H-field, and far field at 10 GHz.
13
Mesh View (I) mesh properties
14
7
21.12.2009
Mesh View (II)
TST at work!
15
Transient Solver: Start Simulation The accuracy defines the steadystate monitor. The simulation is finished when the electromagnetic energy in the computational domain falls below this level.
16
8
21.12.2009
Analyze 1D Results port signals
S-parameter
energy
17
Analyze 2D/3D Results
port information: • cut-off frequency • line impedance • propagation constant 18
9
21.12.2009
Electric Field at 10 GHz
19
Far Field at 10 GHz
20
10
21.12.2009
Polar Plot for Far Field at 10 GHz phi=90
phi=0
Create a new folder “Comparison” to compare different 1D results. 21
Parameterization Optimization
22
11
21.12.2009
Parameterization (I)
r1 outer radius r1 = variable goal: maximize gain
23
Parameterization (II)
outer radius r1
24
12
21.12.2009
Result Processing Templates (Shift+P) 1D results 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. 25
Result Processing Templates (Shift+P) 0D results
Define max of gain(theta).
Read the online help to learn more about the postprocessing in CST MWS. 26
13
21.12.2009
Result Processing Templates (Shift+P) Alternative solution: The maximum gain can be computed using the “Farfield” template in “0D Results”.
Define max of gain(theta).
27
Parameter Sweep - Settings 1
2
3 28
14
21.12.2009
Parameter Sweep - Settings Add a S-parameter watch.
The results will be automatically listed in the “Tables” folder. 29
Parameter Sweep – Table Results Right click on plot window and select “Table Properties…”.
Choose the result curve for each parameter value with the slider.
30
15
21.12.2009
Parameter Sweep – Table Results parameter values
parameter values
31
Automatic Optimization
32
16
21.12.2009
Automatic Optimization Define the parameter space.
Define the goal function.
Template based postprocessing 0D results can be used to define very complex goal functions. 33
Automatic Optimization Choose the “Classic Powell” optimizer.
Follow the optimization.
34
17
21.12.2009
Automatic Optimization - Results parameter values
1D results
goal: maximize gain
35
Optimization - Summary
Define a variable.
Parameterize the structure. Define the goal function. Set the parameter space. Run the optimizer.
36
18
21.12.2009
Far Field Postprocessing
terminology broadband far field analysis co-/cross-polarization phase center tips and tricks
37
Broadband Far Field Analysis How to plot the antenna gain for the complete frequency range?
38
19
21.12.2009
Broadband Far Field Monitors
Create a broadband far field monitor from the available monitors.
After monitor definition, start T-solver again! 39
Result Processing Templates (Shift+P) 1D Results
Define maximum value of gain.
40
20
21.12.2009
Broadband Far Field Monitors far field 3D pattern
41
Broadband Far Field Monitors
42
21
21.12.2009
“Tables” -> “1D Results” -> “Broadband gain 3d”
43
Co- / Cross-Polarization
The co-polarized far field component has the same polarization as the excitation (y-oriented in our case). The cross-polarized far field component is orthogonal to the co-polarized component and main lobe direction. In order to use different polarizations for transmitting/receiving, an antenna design goal might be to maximize the co-polarized and minimize the cross-polarized component. 44
22
21.12.2009
Co- / Cross-Polarization 1. Select the tab “Axes“. 2. Click “Main lobe/polarization alignment“. 3. Choose the “Ludwig 3“ coordinate system.
polarization vector direction (arbitrary user input possible).
45
If “Main lobe ... “ is not selected, the user can enter arbitrary directions for: -polarization plane normal (z„) (= theta axis) -cross-polarized component (x„) (= phi axis).
Co- / Cross-Polarization
co-polarized = Ludwig 3 vertical
cross-polarized = Ludwig 3 horizontal
46
23
21.12.2009
Co & Cross Polarization Result Templates for Parameter Sweep and Optimization co-polarized= Ludwig 3 vertical
cross-pol. = Ludwig 3 horizontal
47
Phase Center Calculation Finding the best location to place the horn inside a parabolic antenna. The best position is to match the focal point of the dish with the phase center of the horn.
= y‘z‘ plane = x‘z‘ plane
?
48
24
21.12.2009
Check Phase Center Check the phase center by plotting the Ludwig 3 vertical phase.
Plotting the phase of Ludwig 3 vertical (=dominant component of co-polarized fields) does not result in a 180° jump of the phase (=color jump) at theta=0. 49
Check Phase Center Check the phase center by moving the origin to the phase center.
50
See also article (Phase Center comparison with measurements) on www.cst.com. -> application article ID=256
25
Workflow Example Horn Antenna Purpose : Optimize the aperture of the horn antenna such that the gain is maximized at 10 GHz.
1
CST MWS - Standard Workflow Choose a project template. Create your model. parameters + geometry + materials
Define ports. Set the frequency range. Specify boundary and symmetry conditions. Define monitors. Check the mesh. Run the simulation. 2
1
21.12.2009
Cylindrical Horn Antenna 8 – 12 GHz 1 0.5 0.5 dia=2, rad=1
zlength=2 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
0.25
3
Project Template At the beginning choose
“File” -> “New”
For an existing project you may choose
to create a new project.
“File” -> “Select Template”.
The project templates customize the default settings for particular types of applications. 4
2
21.12.2009
Project Template background material
Antennas should be modeled with vacuum as background material.
PEC is very practical for closed structures. (e.g. waveguides, connectors, filters)
The project templates customize the default settings for particular types of applications. 5
Change the Units
Define units.
6
3
21.12.2009
Horn Antenna – Construction (I)
Define a brick (1.0 x 0.5 x 0.5 in) made of PEC.
Define a cylinder (outer radius: 1.0 in, height: 0.25 in) made of PEC. 7
Pick face. Align the WCS with the face.
Move the WCS by 2.0 inches.
Horn Antenna – Construction (II)
Pick two opposite faces.
Perform a loft.
8
4
21.12.2009
Horn Antenna – Construction (III) Perform a Boolean add. Select multiple objects (ctrl or shift + left mouse button).
shell solid: 0.01 in (outside)
Pick two faces.
9
Port Definition Pick point inside corner.
Define a waveguide port.
Pick edge.
Define the port on the internal profile. 10
5
21.12.2009
Set the Frequency Range
Set the frequency range.
11
Boundary Conditions and Symmetry Planes
12
6
21.12.2009
3D Monitors
Add field monitors for E-field, H-field, and far field at 10 GHz.
13
Mesh View (I) mesh properties
14
7
21.12.2009
Mesh View (II)
TST at work!
15
Transient Solver: Start Simulation The accuracy defines the steadystate monitor. The simulation is finished when the electromagnetic energy in the computational domain falls below this level.
16
8
21.12.2009
Analyze 1D Results port signals
S-parameter
energy
17
Analyze 2D/3D Results
port information: • cut-off frequency • line impedance • propagation constant 18
9
21.12.2009
Electric Field at 10 GHz
19
Far Field at 10 GHz
20
10
21.12.2009
Polar Plot for Far Field at 10 GHz phi=90
phi=0
Create a new folder “Comparison” to compare different 1D results. 21
Parameterization Optimization
22
11
21.12.2009
Parameterization (I)
r1 outer radius r1 = variable goal: maximize gain
23
Parameterization (II)
outer radius r1
24
12
21.12.2009
Result Processing Templates (Shift+P) 1D results 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. 25
Result Processing Templates (Shift+P) 0D results
Define max of gain(theta).
Read the online help to learn more about the postprocessing in CST MWS. 26
13
21.12.2009
Result Processing Templates (Shift+P) Alternative solution: The maximum gain can be computed using the “Farfield” template in “0D Results”.
Define max of gain(theta).
27
Parameter Sweep - Settings 1
2
3 28
14
21.12.2009
Parameter Sweep - Settings Add a S-parameter watch.
The results will be automatically listed in the “Tables” folder. 29
Parameter Sweep – Table Results Right click on plot window and select “Table Properties…”.
Choose the result curve for each parameter value with the slider.
30
15
21.12.2009
Parameter Sweep – Table Results parameter values
parameter values
31
Automatic Optimization
32
16
21.12.2009
Automatic Optimization Define the parameter space.
Define the goal function.
Template based postprocessing 0D results can be used to define very complex goal functions. 33
Automatic Optimization Choose the “Classic Powell” optimizer.
Follow the optimization.
34
17
21.12.2009
Automatic Optimization - Results parameter values
1D results
goal: maximize gain
35
Optimization - Summary
Define a variable.
Parameterize the structure. Define the goal function. Set the parameter space. Run the optimizer.
36
18
21.12.2009
Far Field Postprocessing
terminology broadband far field analysis co-/cross-polarization phase center tips and tricks
37
Broadband Far Field Analysis How to plot the antenna gain for the complete frequency range?
38
19
21.12.2009
Broadband Far Field Monitors
Create a broadband far field monitor from the available monitors.
After monitor definition, start T-solver again! 39
Result Processing Templates (Shift+P) 1D Results
Define maximum value of gain.
40
20
21.12.2009
Broadband Far Field Monitors far field 3D pattern
41
Broadband Far Field Monitors
42
21
21.12.2009
“Tables” -> “1D Results” -> “Broadband gain 3d”
43
Co- / Cross-Polarization
The co-polarized far field component has the same polarization as the excitation (y-oriented in our case). The cross-polarized far field component is orthogonal to the co-polarized component and main lobe direction. In order to use different polarizations for transmitting/receiving, an antenna design goal might be to maximize the co-polarized and minimize the cross-polarized component. 44
22
21.12.2009
Co- / Cross-Polarization 1. Select the tab “Axes“. 2. Click “Main lobe/polarization alignment“. 3. Choose the “Ludwig 3“ coordinate system.
polarization vector direction (arbitrary user input possible).
45
If “Main lobe ... “ is not selected, the user can enter arbitrary directions for: -polarization plane normal (z„) (= theta axis) -cross-polarized component (x„) (= phi axis).
Co- / Cross-Polarization
co-polarized = Ludwig 3 vertical
cross-polarized = Ludwig 3 horizontal
46
23
21.12.2009
Co & Cross Polarization Result Templates for Parameter Sweep and Optimization co-polarized= Ludwig 3 vertical
cross-pol. = Ludwig 3 horizontal
47
Phase Center Calculation Finding the best location to place the horn inside a parabolic antenna. The best position is to match the focal point of the dish with the phase center of the horn.
= y‘z‘ plane = x‘z‘ plane
?
48
24
21.12.2009
Check Phase Center Check the phase center by plotting the Ludwig 3 vertical phase.
Plotting the phase of Ludwig 3 vertical (=dominant component of co-polarized fields) does not result in a 180° jump of the phase (=color jump) at theta=0. 49
Check Phase Center Check the phase center by moving the origin to the phase center.
50
See also article (Phase Center comparison with measurements) on www.cst.com. -> application article ID=256
25
CST STUDIO SUITE contain the following modules: CST MICROWAVE STUDIO(CST MWS) is the tool use for the fast and Precise 3D simulation of high frequency in TD Time Domain simulation. It also enables the of antennas, filters, couplers, planar and multi-layer structures and SI and EMC effects.