TEM Horn Antenna

ዘካርያስ

Altair Forum User said:

Altair Forum User said:

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 ?

 

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.

ዘካርያስ

Ok thanks,i will try.

ዘካርያስ

Altair Forum User said:

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,

 

 

Mel

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

For example:

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

 

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

ዘካርያስ

Altair Forum User said:

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

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

For example:

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

 

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

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

 

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"?>

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

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

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.

ዘካርያስ

Altair Forum User said:

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' ?

Mel

Create line yes.

ዘካርያስ

Altair Forum User said:

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 ?

ዘካርያስ

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

 

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.

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.

Mel

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

 

6. Something like this?

ዘካርያስ

Altair Forum User said:

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

 

6. Something like this?

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

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 ?

 

 

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.

ዘካርያስ

Altair Forum User said:

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).

 

Mel

See the 2 images below. 

ዘካርያስ

Thanks,

 

I understand !

 

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

 

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

Mel

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

ዘካርያስ

Altair Forum User said:

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"?>

Mel

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

E.g. 

ዘካርያስ

Altair Forum User said:

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

E.g. 

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

Hi Mel,

 

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

Mel

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

ዘካርያስ

Thanks a lot for the invaluable guide !!!