Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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In the name of Allah

“A two dimensional Nx××××Ny array based on “Rectangular Waveguide Aperture Element”

In this example we tried to practice the modelling of two dimensional phased array

configurations with finite array size in CST Microwave Studio.

At the end of this exercise we also analyze an infinite 2D-dimensional array by using Floquet

Excitation instead of waveport.

I appreciate who adds any comment on this work by sending email to:

Smr.razavizadeh@ieee.org, or razavizadeh@yahoo.com

Regards.............Seyed Mohammadreza

Part I: Finite Planar Array Model Design:

>>

Pick the waveguide end faces and then choose shell action for making a waveguide

with thickness:

>>

We have a rectangular waveguide as our main array element. For the future and more

analyze, we can define a material(here Vacuum) inside the waveguide as:

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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The last object is a Radom in front of the array element with epsilon:4 and loss free,

this action can be perform by Extrude based on WG object, pick the front face of WG

and then:

>> >>

Frequency Setting:

Background Material: Setting the propagation region by Background, because the main radiation area is Z>0

in front of the Radom, we set a relative distance based on the largest dimension of the

array element(here waveguide width of “a”, in 3*a), the back of the antenna element

is not important for us because we normally are face with End-closed probe fed

waveguide, later we will set at Boundary setting an PEC(Et=0) wall at Zmin based on

equivalence principle for TE mode excitation :

Excitation Definition:

For waveguide the best choice is

waveport and at Z=0, toward the

positive direction of the Z-axis:

Simulation of Two Dimensional A

Boundary:

As we said previously we have main radiation in Z>0 and no radiation in Z<0, so

based on equivalence principle we can fill PEC material in Z<0 and the equivalent

electric current of the tangential Ey field would be “Ms”. We have a 2

should set the boundary in x and y direction as periodic.

• Phase Setting: In planar antenna array we have two main parameters: progressive excitation phase

array elements of phase_x and

elements distances of dx and d

A schematic view of a N××××N two dimensional Array

In CST MWS we can set the phase parameters by

As shown, our example has a progressive

phase shift only in x-direction as

and “0” all the elements are equal

y-directions.

If you put tick Scan Angle,

the propagation phase constant

surface wave on the array surface in x

direction and is useful for periodic metal,

dielectric structure like EBG, Metamaterial

and ...., for studying the dispersion

behaviour of them.

“The Theta and Phi is the incident plane wave direction when w

floquet excitation instead of period boundary and wave port”.

Antenna Array by using CST-MWS Smr.razavizad

As we said previously we have main radiation in Z>0 and no radiation in Z<0, so

based on equivalence principle we can fill PEC material in Z<0 and the equivalent

electric current of the tangential Ey field would be “Ms”. We have a 2-D array so we

t the boundary in x and y direction as periodic.

In planar antenna array we have two main parameters: progressive excitation phase

and phase_y, in x and y directions, respectively, and

dy.

N two dimensional Array A beam former block diagram

In CST MWS we can set the phase parameters by “phase shift/scan angle”:

As shown, our example has a progressive

direction as “phase_x”

all the elements are equal-phases in

If you put tick Scan Angle, the phase_x is

the propagation phase constant of the

surface wave on the array surface in x-

direction and is useful for periodic metal,

dielectric structure like EBG, Metamaterial

and ...., for studying the dispersion

is the incident plane wave direction when w use the unit cell and

floquet excitation instead of period boundary and wave port”.

deh@ieee.org

As we said previously we have main radiation in Z>0 and no radiation in Z<0, so

based on equivalence principle we can fill PEC material in Z<0 and the equivalent

D array so we

In planar antenna array we have two main parameters: progressive excitation phase of

in x and y directions, respectively, and

of a 2××××2 array

use the unit cell and

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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Postprocessing:

The elements distances of dx and dy could be set via postprocessing as following:

>> >>

Choose “Advanced” Tab, many features are available as below in Farfield setup:

**Array Setup:

*Plot Mode: lin/Log

scale

Result Type: Dir/G/...

Polarization:

Special: Angular Width is the same 3dB-HPBW

*For better viewing the main beam direction the linear scale is better than Log scale.

**As shown in the Array setup window, the important array input data should be

defined in this place.

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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Field Monitor:

For far field, the field monitor should set at Far field/RCS.

Frequency solver: For only field result, we just set the

frequency solver at single sample frequency.

Parametric Sweep:

Far field and template based results:

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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Set what curves which you want to show: click on “None” tab and then:

> >>

Click on Apply and ok:

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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Part II: Infinite Planar Array(Floquet Sources)

Another periodicity can be made by unit cell option in boundary setup. In this case we

should eliminate the excitation and we use the floquet excitation which is based on

two default mode based waveport excitations of Zmin and Zmax.

In this excitation method the antenna acts in receiving mode by exposing by an

incident plane wave source placed on planes of Zmin and Zmax(the results is based

on superposition law for studying the reciprocal peroperties of the system).

Boundary set up of Unit cell in x and y directions:

Floquet Ports: Click on floquet tab and set mode number of ports which are placed at Zmin and

Zmax(for example 2 is ok, because more mode number can alert you low memory

space error!).

>>

Because of setting the Et=0 at Zmin the Zmin source cannot be defined.

Next step is defining the planewave incident direction as “inward”, and at (θ=0, ϕ=0)

directions which is equivalent to “-z” axis direction.

Unit cell setup: We can define any desirable periodic structure like inclined and not right structure

with various distances like below, by correspondent setup:

Standard: if you tick the box result is the same.

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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Diagonal Inclined:

Frequency setup: we can choose a list of port and desired modes.

>>

Results:

Now we want to change the plane wave direction from (θ=0, ϕ=0) to (θ=45, ϕ=0).

Simulation of Two Dimensional Antenna Array by using CST-MWS Smr.razavizadeh@ieee.org

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>>

New Results based on inclined propagation direction: it’s clear that the main back

scattered beam is (θ≅330, ϕ=0) or (θ≅45, ϕ=180).