Cst an Antenna Simulation

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Antenna Simulation

Application Note

CST STUDIO SUITE™

Kra, Jeb / v1.0 / 02. July 2012



Antenna Examples



Simulation Setup



Post Processing



Co/Cross Polarization



Phase Center



Ludwig 3



Antenna Array

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Ready-to-simulate antennas are available here:

Antenna Examples

 CST MWS Examples ->

Transient Analysis Examples -> Antennas -> Overview

 CST MWS Examples -> Integral Solver Examples -> Antennas -> Overview

Online Help ->

(3)

Construct simple Antenna Examples

(4)

Examples

Typical Applications

Solvers

Reflector



_

Parabolic dish

_{Corner reflector}



Communication



Radar



Radio astronomy

Aperture



Rectangular horn



Circular horn



Ridged horn



Waveguide array



Radar



Reflector feed



Calibration standards



Measurement

Wire

(Slot)



Dipole



LPDA, Yagi-Uda



Helix



Printed antennas



Discone



Communication



GPS



EMC measurement



RFID



Almost anything else…

Patch



Rectangular patch



Circular patch



Patch arrays



Radar



Communication



GPS



Imaging

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

Define boundaries as

open (add space)



Define a farfield monitor at

the frequency of interest



Make sure that the

antenna radiates at the

farfield monitor frequency

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

Define a farfield monitor at several frequencies

(macro is available)

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Definition of Farfield Probes

Farfield monitors record the

radiation in all directions for

one frequency.

Farfield probes record the

radiation in one direction for

all frequencies.

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Farfield Definitions

2 2 2 2 1 ) (disabled E E E_R EAbs 2 2 2 1 ) (enabled E E E_Abs

Approximation:

Radiation efficiency:

Total efficiency:

Directivity:

power input accepted power radiated e_rad ) ( power stimulated power radiated e_total power radiated angle solid unit per radiated power D( , ) 4

Component definition:

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Total Radiated Power (TRP)



Macros -> Results -> Farfield -> Show Total Radiated Power (TRP)

Choose linear

or logarithmic

TRP output (in

farfield plot).

Specify power

level in Watt

or dBm.

There are three possibilities to calculate the TRP value:



Results -> Combine Results



Template Based Postprocessing (TBP) -> Farfield and Antenna Properties

-> Farfield Result -> Evaluation Range: 3D -> Result value: TRP

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Total Isotropic Sensitivity (TIS)

TIS handling is very similar to TRP.

Specify receiver

sensitivity

in Watt or dBm.

Specify linear or

logarithmic TIS

output.



Only one (TIS or TRP) can

be displayed at the time.



TIS can also be applied to

CST Design Studio full

system or multi-port

combined results (similar

to TRP).

TIS far-field monitors are created.

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SAR Results

2D or 3D plot including

information about the

position of the maximum.

Opens logfile containing all results.

Visualization of

max. SAR cube

Macros -> Results -> 2D 3D Results -> Plot

Averaging Volume for maximum SAR value

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Diversity / MIMO Antennas

Multiple antennas (

antenna diversity

) may overcome problem of fading dips.

Antenna 1

Antenna 2

„best of“ (diversity gain)

Load farfield of

_{second antenna}

Select from:

• Diversity Gain • Envelope Correlation Coefficient • Multiplexing Efficiency



For lossless antennas in isotropic environment

the correlation and diversity gain can also be

calculated from S-Parameters



TBP -> Farfield Result -> MIMO

Set XPR and power

distribution

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The co-polarized far field component has the same polarization as the

excitation (y-oriented in above 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.

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Co- / Cross-Polarization

Polarization vector direction

(arbitrary user input possible).

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).

1. Select the tab “Axes“.

2. Click “Main lobe alignment“.

3. Choose the “Ludwig 3“ coordinate

system.

(15)

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.

?

= x‘z‘ plane

= y‘z‘ plane

(16)

Circular Polarization

Left and right polarized field components are calculated from the

tangential components:

2 1 2 1

2

1

2

1 iE

E

iE

E

right left

There are two different ways to calculate the circular polarization:



Combine Results

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Ludwig 3

Ludwig 3 vertical

Ludwig 3 horizontal

cos

sin

cos

E

vertical horizontal

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The total farfield of an antenna array can be calculated

in four different ways:



Complete simulation of the array



Array Factor



Periodic Cells (TD-Solver , FD-Solver ) + Array Factor



Unit Cells (FD-Solver ) + Array Factor

Antenna Array

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The accuracy level in the TD-Solver should be -40 dB.

For larger frequency bands (e.g. 0-3 GHz) or poor radiation it is

recommended to use -60 dB so that the E- and H-fields on the

bounding box do not suffer from FFT/DFT truncation errors.

Tip 1: Choose sufficient accuracy.

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The ”open (add space)“ boundary condition ensures λ/8 space at

the center frequency.

For lower frequencies (bigger λ) increase the bounding box size or

adjust the center frequency.

Tip 2: Set appropriate boundary conditions.

(21)

Tip 3: Check the energy balance.

Far field 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).

Tips & Tricks for an Accurate Farfield

At 4.5 GHz the

far field may be

inaccurate.

Cst an Antenna Simulation

Antenna Simulation

Application Note

CST STUDIO SUITE™



Antenna Examples



Simulation Setup



Post Processing



Co/Cross Polarization



Phase Center



Ludwig 3



Antenna Array

Ready-to-simulate antennas are available here:

Antenna Examples

Online Help ->

Construct simple Antenna Examples

Category

Examples

Typical Applications

Solvers

Reflector





Parabolic dish

Corner reflector



Communication



Radar



Radio astronomy

Aperture



Rectangular horn



Circular horn



Ridged horn



Waveguide array



Radar



Reflector feed



Calibration standards



Measurement

Wire

(Slot)



Dipole



LPDA, Yagi-Uda



Helix



Printed antennas



Discone



Communication



GPS



EMC measurement



RFID



Almost anything else…

Patch



Rectangular patch



_

_{Corner reflector}