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help needed for TEM cell feeding in CST

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Oct 1, 2008
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tem cell

i have designed simple tem cell (metalic, air filled and a thin inner septum). I want to get field distribution inside the cell, but I don`t get expected results at all. I define a discret port (between the septum and the case) to feed it and the other end of the cell is left opened (I tried also to place a discrete port there) When starting solver, I get reflection coefficient s11=1, so no field in the cell. What is it wrong defined/set?
Thanks in advance for answering me![/img]

what is tem cell

Could you please upload your model? I can try to simulate the same in EMC Studio (**broken link removed**)

tem cell feed

I saw that EMC can import .sat files, so I have exported the model into a sat file, but I get the message that *sat files are not allowed for upload. I added the .jpg extension also. Hope it works.

cst tem-cell

You can upload archive with SAT file - this is no problem. But project file with settings might be useful as well - better include it in archive. Picture I can not see yet - it is not opened.


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open cell structure tem

In the archive, are both cst and sat files.

Re: TEM cell feeding in CST

Here are results obtained for 300 MHz with your model. Do you need any more specific data to be shown?

Re: TEM cell feeding in CST

Thank you very, very much!
I have few questions: the boundary conditions are same as in cst? (y and z electric boundary and open on the x direction.Is that ok?) What type of excitation have you used? It's curious that the field is so weak in the cell... Anyway I don't know very well how it should look like. I have a paper presenting the Ez component of the field 4 mm above the septum. Could you get a picture of it?
Thank you once again!

TEM cell feeding in CST

Sure, , I can show such picture. But could you please specify required parameter more exactly? Do you mean Ez field in the center of the cell on 4 mm height vs Frequency?
Or you mean Ez component along central line in 4 mm height for some specific Frequency?
For any case - which frequency(ies) you are interested in?

Added after 3 minutes:

EMC Studio simulation is done using Method of Moments solver, which does not require to specify bounding box for the model - free space is not meshed and is considered as open space. TEM Cell structure is considered as PEC metal. Excitation source is 1 V + 50 Ohm between TEM Cell bound and septum (a'la 'lumped port'), the far end of septum is also loaded by 50 hm (this is actually missed in your CST model btw)

Re: TEM cell feeding in CST

I didn't mention: it was Ez component on the x direction for a single frequency (0.837 GHz).
I tried to place a lumped element, a 50 ohms resistor, but got not relevant results. I don't know yet what I'm doing wrong:defining ports or boundary conditions... I'm trying to see what I miss, for the moment reading its Help...
Thank you very much for your kindness!
P.S. I'm sure it's about defining the port. I have 100% reflection at input. Anyway, I define it between a point of the septum and a point of the case, the port being a current source || 50 ohms resistor. I don't understand why my source is "seeing" zero input impedance...

Re: TEM cell feeding in CST

Please take a look on attached EMC Studio MoM results.

About CST port I am not sure how to redefine it. When you will obtain alternative results it would be interesting to compare.


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Re: TEM cell feeding in CST

I had the possibility to run in in FEKO and it worked. I don't understand what was wrong in CST.... I upload few snapshots. I would like to see the field (Ez component, on x-direction at different instants in time. I still cannot find how. They say that Timefeko does this, but it's very few documentation (in my oppinion) about running it.

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