transmmsion line in feko

8/10/2019 Transmmsion Line in FEKO

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1) Lambda/4 transmission Line on finite substrate-

1) Creating the model-The model creation steps that we are going to perform can be summarised

as:1) Set the model unit to millimetres.2) Add variables that define the model geometry and material parameters.3) Add a new dielectric medium type to the model.4) Create the transmission line..5) Create the substrate.6) Create the feed pin to excite the transmission line.7) Union the geometry.8) Add a port and voltage source on the feed pin.9) Set the solution frequency.10) Mesh the model and run the FEKO solver.

You should now have CADFEKO open with an empty model. Lets startconstruction of the model.

The default unit length in CADFEKO is metre. Since the lineThat we are going to build is small we should set the model unit to

Millimetres.


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In the contents tree is a list of predefined variables. To addvariables to the list, right-click on the Variables heading in the tree andselect Add variable in the context menu or use the appropriate buttonfromthe ribbon (Construct tab ! Define group).

Variables are created by entering a variable name and expression andthen clicking on Add. A short comment for the variable can be added tothe Comment field. The including of Comments for variables areoptional.

Add the following variables:

Name Expression

freq 2.4e9er 4.4

lambda c0/freq/sqrt(er)*1000


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w 3l 30

Hs 1.6Ws 15

Ls 30

Media can either be defined by selecting the Construct taband clicking on the Media button (Define group) or by means of thetree. Right-click on the Media in the contents tree and select Createdielectric medium. All dielectric media have to be created before theycan be used in the model.

For the transmission line, we have selected to simulate thesubstrate asa lossless material with a relative dielectric constant of4.4.Select the Dielectric modelling tab and set the Definition method toFrequency independent. Keep the default value of 0 or 0.002 for theDielectric loss tangent and enter the label name d into the Label field.

Ensure that the Construct tab is selected and click on theRectangle button (Create surface group). Under the Definitionmethods, select Base center, width, depth.

Create transmission line.

field valuewidth w


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length l

Now we add the substrate.


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Then check material of substrate.

Next go to property and change it d.


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Also change material for line. Select it go to properties change it toPerfect Electrical Conducter.

Then, Select bottom face and change bottom face of substrate to PEC.


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Now we create the wire pin that feeds the patch.

Then copy line and create second port. Only change sign


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Only change sign

The two geometry parts have to be unioned so that the

segment end points coincide with mesh vertices. Select thetwo geometry parts in the tree (using < Ctrl > ) and click on the

Union button (Modify group).


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After creating the pin, we have to add a port to the feed pin. A portis simply a connection point for loads and excitations. Select Union1in the tree and its corresponding wire in the details tree.

Select the Source/Load tab and click on the Wire port button

The Create wire port dialog is displayed and the edge field isautomatically populated with the correct edge. (The name of the Edgemay differ.) Select Middle to place the port in the middle of the wire.Click Add and Close to create the wire port and close the dialog.

We are now going to add a voltage source to the port.

Ensure that the Source/Load tab is selected, click on the Voltage source


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icon (Sources on ports). The values on the Add voltage source dialog donot have to be changed.Click on Add and Close to create the voltage source and close the dialog.

Click on the Frequency button (Settings group) to set thefrequency range of the simulation. Select the Continuous (interpolated)range and enter the starting- and ending frequency.

Select the Mesh tab end click on the Create mesh button (Meshinggroup) or use the < Ctrl >< M> shortcut to open the Create mesh dialog.


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Save the model by clicking on the Application menu and selectingfromthe menu Save as... and entering a file name. The shortcut keycombinationto save is < Ctrl >< S> .


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Run the FEKO solver by selecting the Solve/Run tab andclicking on the FEKO solver icon (Run/Launch group).

Viewing the resultsThe model creation and simulation process is complete. We can now usePOSTFEKO to view the results. We are going to view phase.The steps are summarised below.

Add another Cartesian graph by selecting the Home tab andclicking on the Cartesianbutton. A second graph is now available with thelabel Cartesian graph1.

Click on the S-parameters data.


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85

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2.20 2.25 2.30 2.35 2.40 2.45 2.50

Frequency [GHz]

S-parameter

S-parameters Phase [deg] (S-parameter = S2,2) - lambda_30mm

SParameters1

transmmsion line in feko

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