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RF domain -> EM waves -> Eigenvalue -> Magnetic field plot?

Posted Jan 27, 2014, 10:35 a.m. EST 10 Replies

State Briga
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Hello,

I have a problem in plotting (or even calculating?) magnetic field in a simple structure and I am using Comsol 4.3a. The structure is a cylinder shape shield (perfect conductor) and inside is a dielectric ring. The thing is that I cannot get magnetic field. It is possible to get electric field and there is no problem, also this is written on the Comsol website: "However, it is no longer possible to solve for the magnetic field H as a dependent variable.". Rest could be found here www.comsol.com/support/releasenotes/4.2/rf/ .

Does anyone know how to plot (calculate) magnetic field from EM wave?

Best.
10 Replies Last Post Jan 28, 2014, 4:20 a.m. EST
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago Jan 27, 2014, 11:02 a.m. EST

Of course you can plot the magnetic field in EM waves. Please be more specific what the issue is. Don't you find the expression in the menus or is the result not what you expect? You might consider to show us your model.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Of course you can plot the magnetic field in EM waves. Please be more specific what the issue is. Don't you find the expression in the menus or is the result not what you expect? You might consider to show us your model. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
State Briga
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Posted: 1 decade ago Jan 27, 2014, 11:31 a.m. EST
Thank you for reply. Maybe it is good to say that this is very first thing I am doing in comsol, so I maybe didn't do all the required steps.

After I set the geometry, I opened Electromagnetic waves, Freq domain. There I set all the values for the wave equation.

From there I get good result for the electric field, but when I try to plot magnetic field it gives only zero. In order to plot it I go for "right click" on results -> 3D plot group -> Slice. In slice expression field I put emw.Hz.

I really do not know if I am not plotting it well, or the problem is that magnetic field is not calculated in the first place.

If anything needs to be clarified, please let me know.
Thank you for reply. Maybe it is good to say that this is very first thing I am doing in comsol, so I maybe didn't do all the required steps. After I set the geometry, I opened Electromagnetic waves, Freq domain. There I set all the values for the wave equation. From there I get good result for the electric field, but when I try to plot magnetic field it gives only zero. In order to plot it I go for "right click" on results -> 3D plot group -> Slice. In slice expression field I put emw.Hz. I really do not know if I am not plotting it well, or the problem is that magnetic field is not calculated in the first place. If anything needs to be clarified, please let me know.
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago Jan 27, 2014, 11:57 a.m. EST
It is not possible to give a better advice without seeing the model. It would just be guessing.

Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
It is not possible to give a better advice without seeing the model. It would just be guessing. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
State Briga
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Posted: 1 decade ago Jan 27, 2014, 12:11 p.m. EST
I am sorry, but unfortunately I cannot upload any file, it gives me "file extension error". Did you thought of attaching some picture or comsol file of what I am doing?
I am sorry, but unfortunately I cannot upload any file, it gives me "file extension error". Did you thought of attaching some picture or comsol file of what I am doing?
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago Jan 27, 2014, 12:18 p.m. EST

I need the model file (.mph).

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
I need the model file (.mph). -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
State Briga
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Posted: 1 decade ago Jan 28, 2014, 3:18 a.m. EST
From different computer I managed to upload a file, and now it is in the attachment.

I would really appreciate if you could give me some further help.

Thank you very much,
Best.

From different computer I managed to upload a file, and now it is in the attachment. I would really appreciate if you could give me some further help. Thank you very much, Best.
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago Jan 28, 2014, 3:48 a.m. EST

I had a look at your model and saw that the magnetic field is phase shifted by exactly 90°. You can see the magnetic field by plotting the norm or by plotting the imaginary component or by looking at the solution at phase angle 90°.

This seems to be a property of your model.
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
I had a look at your model and saw that the magnetic field is phase shifted by exactly 90°. You can see the magnetic field by plotting the norm or by plotting the imaginary component or by looking at the solution at phase angle 90°. This seems to be a property of your model. -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
State Briga
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Posted: 1 decade ago Jan 28, 2014, 4:10 a.m. EST
I can plot magnetic field norm, and it works fine. But still I cannot plot magnetic field component, did you succeed in that?

And could you please tell me how is it possible to change phase for 90deg, or to plot imaginary part?
I can plot magnetic field norm, and it works fine. But still I cannot plot magnetic field component, did you succeed in that? And could you please tell me how is it possible to change phase for 90deg, or to plot imaginary part?
Edgar J. Kaiser Certified Consultant
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Posted: 1 decade ago Jan 28, 2014, 4:14 a.m. EST

As I said, you have to plot the imaginary part (e.g. imag(emw.Hz) ) of the vector field components. Check the documentation for solution phase angle.

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
As I said, you have to plot the imaginary part (e.g. imag(emw.Hz) ) of the vector field components. Check the documentation for solution phase angle. -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
State Briga
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Posted: 1 decade ago Jan 28, 2014, 4:20 a.m. EST
Thank you very much once again.

Your advice is very helpful!
Thank you very much once again. Your advice is very helpful!

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