UniMAP ANTENNAS AND PROPAGATION

LAB 4 1

UNIVERSITI MALAYSIA PERLIS

SCHOOL OF COMPUTER &

COMMUNICATIONS ENGINEERING

EKT 341 ANTENNA AND PROPAGATION

LABORATORY MODULE

LAB 4

3D STRUCTURE ANTENNA SIMULATION

UniMAP ANTENNAS AND PROPAGATION

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Experiment 4 : 3D Structure Antenna Simulation

– Computer Simulation Technology (CST)

OBJECTIVES

Learn how to use and familiarize with CST Microwave Studio Software.

Understanding the basic horn antenna simulation using CST Microwave Studio

Software.

Observing and analyzing horn antenna parameters using CST Microwave Studio

Software.

THEORY OF HORN ANTENNA

The horn antenna is used in the transmission and reception of RF microwave signals, and

the antenna is normally used in conjunction with waveguide feeds. The horn antenna

gains its name from its appearance. The waveguide can be considered to open out or to be

flared, launching the signal towards the receiving antenna. Horn antennas are often used

as gain standards, and as feeds for parabolic or 'dish' antennas, as well as being used as

RF antennas in their own right. One particular use of horn antennas themselves is for

short range radar systems, such as those used for automotive speed enforcement. When

used as part of a parabolic reflector, the horn is orientated towards the reflector surface,

and is able to give a reasonably even illumination of the surface without allowing

radiation to miss the reflector. In this way it is able to maximize the efficiency of the

overall antenna. The use of the horn antenna also minimizes the spurious responses of the

parabolic reflector antenna to signals that are not in the main lobe.

The horn antenna may be considered as an RF transformer or impedance match between

the waveguide feeder and free space which has an impedance of 377 ohms. By having a

tapered or having a flared end to the waveguide the horn antenna is formed and this

enables the impedance to be matched. Although the waveguide will radiate without a

horn antenna, this provides a far more efficient match. In addition to the improved match

provided by the horn antenna, it also helps suppress signals travelling via unwanted

modes in the waveguide from being radiated. However the main advantage of the horn

antenna is that it provides a significant level of directivity and gain. For greater levels of

gain the horn antenna should have a large aperture. Also to achieve the maximum gain

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for a given aperture size, the taper should be long so that the phase of the wave-front is as

nearly constant as possible across the aperture. However there comes a point where to

provide even small increases in gain, the increase in length becomes too large to make it

sensible. Thus gain levels are a balance between aperture size and length. However gain

levels for a horn antenna may be up to 20 dB in some instances.

There are two basic types of horn antenna: pyramid and conical. The pyramid ones, as the

name suggests are rectangular whereas the corrugated ones are usually circular. The

corrugated horn provides a pattern that is nearly symmetrical, with the E and H plane

beamwidths being nearly the same. Additionally it is possible to control the side lobes

better with a conical or corrugated horn antenna. The horn antenna is a particularly useful

form of antenna for use with RF microwave applications and waveguide feeder. Although

it is not used below RF microwave frequencies because waveguides are not used at low

frequencies as a result of the sizes needed, the horn antenna is nevertheless a very useful

form of RF antenna design for use at high frequencies.

CST MICROWAVE STUDIO STANDARD WORKFLOW;

a) Choose Project Template

b) Specify Units (Frequency - GHz, Time – ns and Dimension - cm)

c) Parameters + Geometry + Materials

d) Ports

e) Frequency-range + Boundaries / Symmetries

f) Monitor Definition

g) Quick Check Meshing

h) Run Simulation

HORN ANTENNA DESIGN

Figure shows horn antenna with specifications and parameters to be monitored.

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SIMULATION USING COMPUTER SIMULATION TECHNOLOGY (CST) SOFTWARE

1. Select the appropriate Studio (1) which is CST Microwave Studio. To select

template for a horn antenna, click Antenna [Horn,Waveguide].

2. Set the antenna units by click the icon , and click the icon , to define

the frequency range of horn antenna at Fmin = 4 GHz and Fmax = 6 GHz.

[1]

[2]

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3. Select the [1], for brick dimension is as follows, 4.0 x 2.0 x 3.0 . Then click [2],

Pick Face for the brick, and click [3] to Extrude, with Height 10 and Taper 25

(deg) .

4. The total solid objects/structures now are two. To combine both structures, select

both components and click Boolean Add, and this will add two structures into

one.

Boolean Add

[1] [2] [3]

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5. Click Pick Face on each side (front and rear faces).

6. Find Objects Shell Solid or Thicken Sheet. (0.1 Outside)

7. For Port definition, click Pick Face to Face 2 edges then move on to

waveguide ports.

Face 1

Face 2

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8. Boundary condition and Symmetry planes

a) An antenna is normally being characterized (using network analyzer) with

free space surrounding. Therefore, use Boundary Conditions Boundaries,

open [add space] for all boundaries to simulate this environment.

b) By knowing that the E plane is YZ plane and H plane is XZ plane for horn

antenna, please set YZ plane magnetic [Ht = 0], XZ plane electric

[Et =0] and XY plane none

Boundary condition Symmetry planes

9. Mesh view and 3D Monitor

Click Mesh View icon and set Lines per wavelength = 5, lower mesh

limit = 5, and mesh line ratio limit = 10. Such settings would make the

simulation faster.

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Please click Solve Field Monitors to ensure the E Field, H Field/Surface

current and Farfield/RCS is clicked for the 3D Monitor.

10. Starts Simulation

For Solver settings, click Solve Transient Solver. Then, set the accuracy

at -30dB, by clicking Accuracy -30dB, and then click Start

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Analyze and explain the result from the question;

1. When the simulation is completed, from the navigation tree,

Find and analyze the result for;

a) 1D results Port Signal

b) 1D results |S|dB

c) 1D results Smith chart

d) 1D results Energy

2. Find the VSWR . Click, Results S parameter Calculations Calculate

VSWR.

3. With the same navigation tree, observe 2D/3D results for E-field and H-field at

the port for the surface current.

4. For electric field observation, click 2D/3D ResultsE-fieldY right click

on horn antenna check animate fields.

5. CST Microwave Studio also can generate 3D view of farfield radiation pattern.

a) Get the 3D view by clicking Farfields farfield (f=5) [1] Abs.

b) Then, Right click Plot properties farfield and structure view check

show structure. Then, click Apply Ok.

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6. 3D can be also plotted into 2D, by right clicking of plot properties and change

plot type to Polar. Right click Plot properties Plot type Polar.

Results for 2D should get same as figure below.

7. State your observation for question 3, 4, 5 and 6 in your report.