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TEM Horn Antenna

User: "ዘካርያስ"
Altair Community Member
Updated by ዘካርያስ
Hi i am practicing on altair FEKO student edition.

I have completed my TEM horn antenna design in paper using exponential tapering but i need a hint how i can model it in FEKO.

 

How i can model the TEM geometry on FEKO ?

 

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    User: "Mel"
    Altair Employee
    Updated by Mel

    If you have an equation for the exponential tapering, you could try the analytical curve.

    A curve can be changed into a surface(s) using sweep for example, or one or more of the other operators in the Extend group (right) on the Construct tab in CADFEKO.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    Ok thanks,i will try.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    If you have an equation for the exponential tapering, you could try the analytical curve.

    A curve can be changed into a surface(s) using sweep for example, or one or more of the other operators in the Extend group (right) on the Construct tab in CADFEKO.

    Hi,

    I am trying on the analytical curve in parametric interval i.e. i entered the exponential taper equation for height of the TEM horn and also another exponential equation for the width of the TEM horn per my design but the geometry couldn't be generated. Shape of the required TEM horn is the below,

     

    image.png.1508ee2ed90dbf4705c09175733ab6ca.png

     

    User: "Mel"
    Altair Employee
    Updated by Mel

    Try lofting the analytical curves of the two outside edges as seen in the images below.

    curves.png

    For example:

    <?xml version="1.0" encoding="UTF-8"?>curve1_geom.png

     

    The position of the curves you can control with the workplane tab.

    curve1_workp.png

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    Try lofting the analytical curves of the two outside edges as seen in the images below.

    <?xml version="1.0" encoding="UTF-8"?>curves.png

    For example:

    <?xml version="1.0" encoding="UTF-8"?>curve1_geom.png

     

    The position of the curves you can control with the workplane tab.

    <?xml version="1.0" encoding="UTF-8"?>curve1_workp.png

     

    Hi,

     

    Thanks a lot  for your assistance, i have created the TEM horn using the exponential equations in Cartesian-parametric interval per my design as shown in the attachment.

     

    Now i am going to excite the antenna via a 50 Ohm coaxial line without a balun,is that possible to choose wire port.

     

    Note:-  The upper and lower conductors of the antenna are in union and at the origin the distance b/n the upper and lower conductors is 2 mm (0.2 cm).

     

    Best regards,

    <?xml version="1.0" encoding="UTF-8"?>Port @edge.PNG

    <?xml version="1.0" encoding="UTF-8"?>image.png

    <?xml version="1.0" encoding="UTF-8"?>FEKO Tx-Rx Antenna.PNG

    User: "Mel"
    Altair Employee
    Updated by Mel

    You can user a wire port, yes.

    Click on the Line primitive, and use CTRL+SHIFT to snap to the edge centers of the top and bottom edges of your first image above to connect the line. 
    You must then Union the line with the horn.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    You can user a wire port, yes.

    Click on the Line primitive, and use CTRL+SHIFT to snap to the edge centers of the top and bottom edges of your first image above to connect the line. 
    You must then Union the line with the horn.

     

    Is 'Line primitive' same as 'Create Line' ?

    User: "Mel"
    Altair Employee
    Updated by Mel

    Create line yes.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    Create line yes.

    Hi Mel,

     

    Thanks for the usual unreserved assistance.

     

    I applied a wire port(segment) in the middle of a line, first by creating a line which starts @ (0.0,0.0,0.1) and ends @ (0.0,0.0,-0.1) then Unioned with TEM horn antenna.

    Note:-
    > The middle of edge of upper conductor of the TEM is (0.0,0.0,0.1).
    > The middle of edge of lower conductor of the TEM is (0.0,0.0,-0.1).
    > Unit measurement is made in cm.

     

    Below are my requests to proceed in my simulation.

     

    1. How to request near and far field with respect to the TEM antenna size(example 40 cm length horn) ?

    2. How to select mesh size with respect to TEM antenna size(Standard mesh is slected then what should be the wire segment example for 40 cm length horn) ?

    3. How to select Frequency range in FEKO since only a single frequency selection option is available ?

    4. Limitation of FEKO student edition with respect to TEM horn antenna size(example for 40 cm long horn) ?

    5.What is the cause for delayed simulation in FEKO ?

    6. How to immerse a dielectric in TEM horn antenna(As we know a dielectric can only be applied in closed regions) ?

    7.Is that possible to apply a pulse in simulation ?

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    For #3 there is multiple freq option,please ignore that query.

     

    User: "Mel"
    Altair Employee
    Updated by Mel

    1. The example guide examples D4 (Radhaz example) and F2 (MRI) shows how to create near field requests. 
    For far fields, several examples show creation of far field requests. Just search for 'far field'. 
    In terms of the number of points/increments, if unsure, you can always request continuous far fields. Example H3 (reflector antenna) shows how to do this.
    2. The wire radius should be according to the physical size that would be used, e.g. SMA has a radius of 0.65 mm.
    3. Search the Examples Guide for 'continuous frequency range' or 'linearly spaced discrete points', there are frequency list and logarithmic options too.
    4. The student edition limits are provided here. https://altairuniversity.com/feko-and-winprop-student-edition-limitations/
    If you need higher limits, contact your study leader for access to the full Feko license.
    5. Please clarify what you mean by delayed?
    6. Please clarify, maybe give a drawing of what you are planning to do.
    7. Yes, see Examples Guide G1 Time Domain.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    Thanks for the response.

     

    Here are the clarifying points.

     

    5.While requesting near fields for a 40 cm TEM in CADFEKO,it takes long time to respond.

     

    6.I want to change the free space b/n the upper and lower conductors of the TEM horn by a dielectric media and see the effect on coupling on receiver antenna.

     

    I appreciate your quick response as usual.

     

    》》If not clear please let me know.

    User: "Mel"
    Altair Employee
    Updated by Mel

    5. How many points in total have you requested for the near field?

     

    6. Something like this?

    image.png

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    5. How many points in total have you requested for the near field?

     

    6. Something like this?

    <?xml version="1.0" encoding="UTF-8"?>image.png

    Thanks Mel,

     

    5. I will work per the guide on 'near field' request and will come back if i encounter difficulty.

     

    6. Yes,the dielectric material is to be filled as shown in the figure you indicated  i.e. in the free space b/n upper and lower conductors of the TEM horn. Any guidance how to do that ?

     

     

    User: "Mel"
    Altair Employee
    Updated by Mel

    I made lofts between the two PEC surfaces. This then creates a solid which has a region that you can set to dielectric,

    Then change the face properties to either PEC or dielectric.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    I made lofts between the two PEC surfaces. This then creates a solid which has a region that you can set to dielectric,

    Then change the face properties to either PEC or dielectric.

    Dear Mel,

     

    Would you mind elaborating it ? 

     

    For your further info below is pic that shows dielectric filled TEM(i found it from a certain publication).

     

    image.png.6323c9bbaf1ceac0956d7c6036d13a9b.png

    User: "Mel"
    Altair Employee
    Updated by Mel

    See the 2 images below. 

    loft.png

    facespec.png

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    Thanks,

     

    I understand !

     

    But the below error message is appearing as i am using student edition.

     

    <?xml version="1.0" encoding="UTF-8"?>image.thumb.png.acfbf55cd19db5cc8dd518b5f43e5ba9.png

    User: "Mel"
    Altair Employee
    Updated by Mel

    You will have to use the University's full license then.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    You will have to use the University's full license then.

    Hi Mel,

     

    I continued working on the student version and i am able to create the dielectric media in the TEM horn.

     

    I set up the upper and lower conductors of the horn as PEC and the remaining faces as a dielectric boundary. 

     

    But there is an error message while creating a wire port as shown below.

     

     

    <?xml version="1.0" encoding="UTF-8"?>image.thumb.png.00cf6090ab9ccce16e165af3d1aad2b0.png

    User: "Mel"
    Altair Employee
    Updated by Mel

    The wire can't be on the surface of the dielectric. Either inside our outside.

    E.g. 

    image.png

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    The wire can't be on the surface of the dielectric. Either inside our outside.

    E.g. 

    <?xml version="1.0" encoding="UTF-8"?>image.png

    Hi Mel,

     

    Make two wires(lines) that join at their end,right ?

    User: "Mel"
    Altair Employee
    Updated by Mel

    Yes, two wires joined or a Polyline will do the job.

    User: "ዘካርያስ"
    Altair Community Member
    OP
    Updated by ዘካርያስ

    Thanks a lot for the invaluable guide !!!