Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

Mode Analysis, Eigenfrequency, and Frequency-Domain Modal

Please login with a confirmed email address before reporting spam

Hello,

I am working with comsol 4.4, and I know I can use the mode analysis to get the modes of a waveguide or a resonant cavity. However, I wanted to perform a mode analysis of a patch antenna to get the characteristic modes over frequency. Could anyone tell me how to run the mode analysis or the Freuqency-Domain Modal solver with conductive structures? I am currently running a model like that, but none of the mode solutions make any sense.

Thank you.


6 Replies Last Post Feb 12, 2020, 2:21 AM EST

Please login with a confirmed email address before reporting spam

Posted: 7 months ago Aug 15, 2019, 1:41 AM EDT
Updated: 7 months ago Aug 15, 2019, 1:41 AM EDT

You can have your patch antenna and computational domain (vacuum, I assume) surrounded by perfectly matched layers. Then it is possible to solve for the eigenfrequencies and eigenmodes (or characteristic modes). Without further information (a model file the best), it is hard to see where your problem is.

-------------------
ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
You can have your patch antenna and computational domain (vacuum, I assume) surrounded by perfectly matched layers. Then it is possible to solve for the eigenfrequencies and eigenmodes (or characteristic modes). Without further information (a model file the best), it is hard to see where your problem is.

Please login with a confirmed email address before reporting spam

Posted: 7 months ago Aug 16, 2019, 11:14 AM EDT
Updated: 7 months ago Aug 16, 2019, 11:14 AM EDT

Hi Pu,

Thanks for the reply. I am attaching my model file. Characteristic modes are supposed to be real values, and I am getting imaginary eigenfrequencies. Also, do you know how to export the eigenvectors for the corresponding eigenvalues?

Jose Santos.

Hi Pu, Thanks for the reply. I am attaching my model file. Characteristic modes are supposed to be real values, and I am getting imaginary eigenfrequencies. Also, do you know how to export the eigenvectors for the corresponding eigenvalues? Jose Santos.


Please login with a confirmed email address before reporting spam

Posted: 7 months ago Aug 16, 2019, 8:50 PM EDT
Updated: 7 months ago Aug 16, 2019, 8:50 PM EDT

I have a brief look at your model. First of all, I don't understand why you are using a 2D model. Shouldn't a patch antenna be a real-world 3D thing? And the eigenfrequencies actually should be complex, as the modes are loosing energy through radiation. About exporting eigenvectors, I'm not sure what you meant.

Best

-------------------
ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
I have a brief look at your model. First of all, I don't understand why you are using a 2D model. Shouldn't a patch antenna be a real-world 3D thing? And the eigenfrequencies actually should be complex, as the modes are loosing energy through radiation. About exporting eigenvectors, I'm not sure what you meant. Best

Please login with a confirmed email address before reporting spam

Posted: 7 months ago Aug 20, 2019, 11:59 AM EDT

Hi Pu,

I was trying to model the patch antenna as a crossection modeling only the conducting element. I undestand now that the eigenfrequencies should be complex, but according to documentation, the eigenfrequency and the eigenvalue study should be similar. However, I am getting different results with them. Do you have any suggestion of how I should model this? Also, where can I find more information about the eigenfrequency solver and its physical interpretation?

Respectfully, Jose Santos.

Hi Pu, I was trying to model the patch antenna as a crossection modeling only the conducting element. I undestand now that the eigenfrequencies should be complex, but according to documentation, the eigenfrequency and the eigenvalue study should be similar. However, I am getting different results with them. Do you have any suggestion of how I should model this? Also, where can I find more information about the eigenfrequency solver and its physical interpretation? Respectfully, Jose Santos.

Please login with a confirmed email address before reporting spam

Posted: 7 months ago Aug 20, 2019, 7:01 PM EDT

I don't get the cross section modeling thing. Can you explain it a bit?

Eigenfrequency and eigenvalue modules are indeed the same in essence. The results should be same. The only differences are some definitions.

I'm not aware of COMSOL calculation of characteristic modes, but the software is commonly used to calculate quasi-normal modes of metallic nanostructures at optical frequencies (similar to your study). You can find relevent information on the internet.

-------------------
ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
I don't get the cross section modeling thing. Can you explain it a bit? Eigenfrequency and eigenvalue modules are indeed the same in essence. The results should be same. The only differences are some definitions. I'm not aware of COMSOL calculation of characteristic modes, but the software is commonly used to calculate quasi-normal modes of metallic nanostructures at optical frequencies (similar to your study). You can find relevent information on the internet.

Please login with a confirmed email address before reporting spam

Posted: 2 months ago Feb 12, 2020, 2:21 AM EST

Hi Jose,

Have you found any way to export the eigenvectors for the corresponding eigenvalues?

Best,

-------------------
Phan
Hi Jose, Have you found any way to export the eigenvectors for the corresponding eigenvalues? Best,

Reply

Please read the discussion forum rules before posting.

Please log in to post a reply.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.