experiment # 1 introduction to cst commu… · winter 2013/2014 information engineering and...

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Information Engineering and Technology

Communication Lab (COMM 703)

Berlin Campus

Experiment # 1

Introduction to CST

Abstract This experiment is an introduction to CST software (Computer Simulation

Technology) which is powerful numerical full electromagnetic simulator. It simplifies solving complex structures as it solves for Maxwell’s equations

numerically inside the structure. CST gives a complete insight about the E & H fields behaviors within the structure in either time or frequency domain. It

also enables prediction of designed circuit response before going into the complicated and costly process of fabrication.

This experiment introduces the following: Creating new project

Setup a new design GUI introduction

Creating a microstrip transmission line (MLIN) design. Simulation of the MLIN

Results extraction and evaluation

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Creating a new project

1) From the start-up menu shown below, choose CST Microwave Studio

2) Afterwards, from the design template menu choose <None>.

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3) Next, the CST Microwave Studio Interface appears as shown below.

Drawing Area

Message Window Parameters List

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Units Definition

From the main menu tool bar choose Solve>> Units Set the dimensions to be in (mm.) and the frequency to be in

GHz

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Background properties

From the main menu tool bar choose Solve>> Background

material. Set the material type to be >> Normal as shown below.

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Frequency Range

From the main menu tool bar choose Solve>> Frequency. Adjust the min and max frequency.

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Boundary Conditions

From the main menu tool bar choose Solve>> Boundary Conditions. ( Free space)

Choose the boundary condition to be Open and mark “Apply in all directions”.

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Introductory Example

To get familiar with the EM simulation tool, an introductory example is

illustrated below aiming to simulate the EM fields in a 50 Ω microstrip transmission line in a frequency range from 1 to 5 GHz.

Procedure: 1. Draw the microstrip transmission line as shown in figure below.

The material of the substrate is FR4 with relative permittivity of 4.4 and thickness of 1.5 mm.

parameter value W 20

L 30

h 1.5

εr 4.3

First of all define the three parameters of the substrate “Length, Width and height” in the parameters list bar.

h εr

W

L

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From the main menu tool bar choose Objects>> Basic Shapes

>> Brick.

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Define the substrate’s parameters in the menu shown below.

And from the Material icon >> Load from Material Library and

choose Fr4 (loss free).

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After clicking load then ok from the parameters list menu. The

Substrate is drawn as shown below

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2. Assign the lower surface as perfect conductor boundary (Ground).

3. Draw the strip on the upper surface as a rectangle with dimensions 2.8x20 mm. then assign this rectangle as perfect

conductor (PEC). The width of the microstrip transmission line is determined to

be 2.8 mm in order to maintain a perfect match of the MTL to 50 Ω.

4. In order to excite the EM wave inside the microstrip transmission

line, 2 waveguide ports are created.

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Mesh Properties From the main menu bar choose mesh>> Global Mesh

Properties.

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Transient Solver From the main menu bar choose Solve>> Transient Solver.

From the above menu, Click Start to start the simulation.

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Results

After completing the simulation, from the navigation menu, choose 2D/3D results >> Port modes>> Port1>> e1 >> X

as shown

From the menu on the left, some important wave parameters are indicated like the propagation constant β and wave

impedance as shown. It is also clear that the MTL impedance is kept to 51.155 Ω.

Investigating the S-Parameters, from the navigation list >>

1D Results >> S-Parameters.

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Requirements

1) Repeat the simulation of the MTL but this time it is required to

match it to 75 Ω instead of 50Ω of the introductory example. 2) Calculate the β, λg

3) Plot the S-Parameters (magnitude and phase). 4) Plot S21 and S12 individually ( magnitude and phase)

5) Plot S11 and S22 individually (magnitude and phase).