how to plot mutual impedance between two antenna elements as a function of separation between them ?

mgmv7

Good Time ! @JIF

 

Can you help me how to plot mutual impedance between two antenna elements as a function of separation between them in parallel and collinear configuration?

So far what I did is , i have takes S-parameters for each corresponding distance and converted to Z parameters using S-Z formula conversion and dumped those values in matlab and plotted the graph for mutual impedances for the corresponding distances? Is it the way or do we have any direct method?

 

Madelé

Hello

 

There is an example available with the Parameter Sweep script on Script Exchange (https://altairhyperworks.com/ > Resources > Script Exchange) that might be of help. In this example, the mutual impedance graphs are plotted in POSTFEKO for two collinear and two parallel dipoles. The input impedance of the dipole is obtained by reading it off a graph, but it could of course also be obtained by exporting the Z-parameters of VoltageSource1 for the single dipole (dipole_length_optimised.cfx model).

mgmv7

Thank you so much for the reply.Will definitely look into it .

mgmv7

Hello !

I have got the post feko graph page but in the stored data I got voltage source1_sweep and voltage source1_sweep_1. I am bit confused , from which I get real and imaginary self impedance graphs ?

Madelé

Hello @mgmv7

 

In the simple parameter sweep example where the mutual impedances of two of the same dipoles are plotted, the calculation is done on the trace itself (using 'Enable maths') where the dipole's input impedance (read from a graph in the model with the single dipole, or obtained from the exported Z-parameters) gets subtracted. 

 

 

You would also be able to do this using Lua scripting, especially if you have more complex calculations in mind.

 

Kind regards

Madelé 

 

mgmv7

Thank you @MvdM

 

Here is my problem.

 

I need to calculate mutual coupling  (Z12) between two identical half wave dipoles both in parallel and collinear configuration.  The radius of the wire is 1e-5lambda and the operating frequency is 200MHz. BOTH MY DIPOLES ARE PLACED IN FREE SPACE.For this case, I am following Sweep parameter example .

I have few questions regarding my problem , simulating in FEKO.

1. I Shall take global radius as 1e-5lamba. Is it correct?

2. Should I follow same method like the example for half wave dipole parameter sweep i.e, calculating length scale then putting the evaluated length scale back and calculating  self impedance?

3. I need to vary distance(d)  from 0 to 15lambda in  parallel configuration

4. What is the mesh size I shall take? How many samples I shall have?

3. What necessary modifications should I make in example to meet my problem requirements?

 

I have tried but I am not confident about my results.

 

 

I SHALL BE THANKFUL TO YOU IF YOU ANSWER MY QUESTIONS.

 

 

 

 

 

mgmv7

@ MvdM 

Can you reply to my above question ?

Madelé

Hello @mgmv7

 

Just browsing the forum, you would find some helpful advice, for example:

 

https://community.altair.com/community?id=community_question&sys_id=28a6c47a1b2bd0908017dc61ec4bcbc7

 

 

For the segment radius, I would suggest that you use the radius that you need to simulate - don't make the wire infinitely thin thinking the answer is more correct for some reason. If the ratio of the radius to length become to extreme, then it is time to use a cylinder (triangles) instead of segments. What I mean by 'extreme' is that the MoM segments uses a thin wire model and the approximation becomes better the longer the segment is relative to its radius (or rather, the smaller the radius for a given segment length). You can get good results even with relatively fat segments (5 to 1 ratio). FEKO will give a warning and eventually an error if the segments are too think compared to the segment length.

 

https://community.altair.com/community?id=community_question&sys_id=35864c3a1b2bd0908017dc61ec4bcb29

 

 ...mesh size refers to the edge / segment lengths. The radius is more a model parameter. When you build an antenna, you select a particular wire with a particular radius (model parameter). The meshing on the other hand is a 'simulation parameter' and has nothing to do with the actual (real life) model - it is simply a requirement for the simulation.

2

You should enter the wire radius value that matches the dimension of the structure you are modelling.

 

What you need to simulate really depends on the problem that you are trying to solve. If you know the length of the dipole antenna, then you do not need to do a parameter sweep to determine its length. If you need to determine the optimum length of the antenna, you could follow the steps in the example.

To get started, you can use automatic meshing (for example, select 'Standard' for the mesh size on the meshing dialog). Please refer to the user guide for more information on meshing and automatic meshing. If you'd like to familiarise yourself with the basic concepts, you can work through the Altair Feko Getting Started Guide and the section(s) of interest like 'Antenna Synthesis and Analysis' in the Altair Feko Examples Guide.

mgmv7

@MvdM

 

Thank you so much for the reply . Will look into those  examples .