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Microstrip patch antenna

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Hi,

I am trying to design a microstrip patch antenna in comsol multiphysics software. I saw a video on youtube in which they were designing it in CST software. I had the student version of CST software, so i followed the step in the video and designed the antenna. The results obtained from the antenna in my CST software were good. However, now i am trying to design the same antenna with all same parameters in comsol multiphysics and getting awful results.

My problem is in CST they were using wave port for exciting the antenna, which was very big and almost floating in the air. In my case, in comsol, i am using lumped port for it. which is very small in size than the waveport of CST.

Can anyone tell me how should i get the good results in comsol software, the only difference which i can see in designing the antenna in CST and comsol is waveport.

Please help


8 Replies Last Post 23 feb 2019, 22:59 GMT-5
Robert Koslover Certified Consultant

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Posted: 6 years ago 21 feb 2019, 12:23 GMT-5

If you want to simulate the true (or nearly true) field distribution at the feed, then instead of using the lumped-port approximation, you need to first solve for the field distribution there, to use in exciting the antenna. There are at least a couple of ways to do this. Look at the examples involving boundary-mode calculations. Also, for TEM-line excitations, you can often solve for the fields with the electrostatic model, then use them to drive your RF model.

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Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
If you want to simulate the true (or nearly true) field distribution at the feed, then instead of using the lumped-port approximation, you need to first solve for the field distribution there, to use in exciting the antenna. There are at least a couple of ways to do this. Look at the examples involving boundary-mode calculations. Also, for TEM-line excitations, you can often solve for the fields with the electrostatic model, then use them to drive your RF model.

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Posted: 6 years ago 22 feb 2019, 00:27 GMT-5

Thankyou so much for your reply sir,

Could you please guide me in where i can see these (boundary mode calculations) examples? I have looked around application library of comsol multiphysics but all the examples there are using either lumped port or port boundary condition for exciting the antenna.

I have attached the microstrip patch antenna model made in comsol and CST below.

Just to highlight again:- My problem is, i am using the same parameters to model an antenna in comsol and CST, the results (S11 = -20dB, directivity in particular direction) obtained in CST are good. However, in comsol its very different (S11= -15dB, directivity spread all side).

The only difference that i can see in both the models is this wave port used in CST, shown in the attached file. As you can see in the diagrams, the wave port is somewhat floating in the air. I don't know where is wave port in comsol.

So, in comsol, I am using lumped port as shown in attached file. The volatge used is 1[V] and input impedence is 50 ohm.

Please help.

Thankyou so much for your reply sir, Could you please guide me in where i can see these (boundary mode calculations) examples? I have looked around application library of comsol multiphysics but all the examples there are using either lumped port or port boundary condition for exciting the antenna. I have attached the microstrip patch antenna model made in comsol and CST below. Just to highlight again:- My problem is, i am using the same parameters to model an antenna in comsol and CST, the results (S11 = -20dB, directivity in particular direction) obtained in CST are good. However, in comsol its very different (S11= -15dB, directivity spread all side). The only difference that i can see in both the models is this wave port used in CST, shown in the attached file. As you can see in the diagrams, the wave port is somewhat floating in the air. I don't know where is wave port in comsol. So, in comsol, I am using lumped port as shown in attached file. The volatge used is 1[V] and input impedence is 50 ohm. Please help.


Robert Koslover Certified Consultant

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Posted: 6 years ago 22 feb 2019, 18:59 GMT-5

I've attached an example (my own) of a parallel-plate TL with two numeric TEM RF ports, where the fields on the ports are first solved using the boundary-mode method. You can also compute the S parameters and impedance, which I included in the Results section.

I hope this simple model helps you enough so that you can figure out the rest of what you need to do. Good luck.

Enjoy.

-------------------
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
I've attached an example (my own) of a parallel-plate TL with two numeric TEM RF ports, where the fields on the ports are first solved using the boundary-mode method. You can also compute the S parameters and impedance, which I included in the Results section. I hope this simple model helps you enough so that you can figure out the rest of what you need to do. Good luck. Enjoy.


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Posted: 6 years ago 23 feb 2019, 03:44 GMT-5

Thankyou sir,

But, i'm not able to open your file in my comsol version. The comsol version which you are using is 5.4 and mine is 5.2.

Can you suggest some other way?

Thankyou sir, But, i'm not able to open your file in my comsol version. The comsol version which you are using is 5.4 and mine is 5.2. Can you suggest some other way?

Edgar J. Kaiser Certified Consultant

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Posted: 6 years ago 23 feb 2019, 06:38 GMT-5

The Comsol1 picture seems to show that the ground plane is only under the feed line and not under the patch. A patch antenna needs a proper ground plane.

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Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
The Comsol1 picture seems to show that the ground plane is only under the feed line and not under the patch. A patch antenna needs a proper ground plane.

Robert Koslover Certified Consultant

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Posted: 6 years ago 23 feb 2019, 18:58 GMT-5
Updated: 6 years ago 23 feb 2019, 18:59 GMT-5

Well, if you have an active license, I suggest upgrading to the latest Comsol version. It is always best to have the latest version, if you can. But if not, perhaps another person reading this forum can help you by providing some other example in v5.2 or earlier. Good luck.

-------------------
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
Well, if you have an active license, I suggest upgrading to the latest Comsol version. It is always best to have the latest version, if you can. But if not, perhaps another person reading this forum can help you by providing some other example in v5.2 or earlier. Good luck.

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Posted: 6 years ago 23 feb 2019, 22:38 GMT-5

Hello sir edigar,

I make the ground plane partial to have the wideband. If i make the groud plane size of substrate then the anteena becomes narrow band.

Hello sir edigar, I make the ground plane partial to have the wideband. If i make the groud plane size of substrate then the anteena becomes narrow band.

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Posted: 6 years ago 23 feb 2019, 22:59 GMT-5

Thankyou for you help sir robert.

Thankyou for you help sir robert.

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