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Integrating two RF application modes

Posted Feb 21, 2010, 6:22 a.m. EST RF & Microwave Engineering, Geometry Version 3.5a 6 Replies

Shakeeb Bin Hasan
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I want to simulate a 3D waveguide geometry using 3D transient wave propagation mode of RF module. The input field at one of the far cross-sections is an eigen-mode of the waveguide.

I create a multiphysics models with both 3D Electromagnetic waves transient wave propagation and 2D perpendicular waves application modes included. The latter is used to define the cross-section of the waveguide which is then simply extruded into a 3D object for 3D transient wave propagation.

After solving the eigen-mode using 2D perpendicular waves analysis, I want to put in the generated field distribution in one cross-sectional boundary of the extruded 3D waveguides. But the problem is how to access the 2D field distribution in this extruded 3D geometry?

Intuitively, I tried defining Extrusion coupling variable in the 2D geometry and selected the desired boundary of 3D geometry as destination. But this doesn't work The variable is not recognized in the scope of 3D geometry.

I will really appreciate if someone could inform me on how to make do with this thing as I am really exhausted searching through manuals in vain. Please let me know if I need to clarify the question or settings more.

Thanks in anticipation.
6 Replies Last Post Jun 6, 2013, 8:26 a.m. EDT
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Hello Shakeeb Bin Hasan

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Jing Wen
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Posted: 1 decade ago Jan 17, 2011, 8:30 a.m. EST
Hi, I have exactly the same problem as you had. Did you find a solution already?
Hi, I have exactly the same problem as you had. Did you find a solution already?
Shakeeb Bin Hasan
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Posted: 1 decade ago Jan 20, 2011, 5:03 a.m. EST
Yes, I think I did. What specifically you want to know and which version?
Yes, I think I did. What specifically you want to know and which version?
Jing Wen
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Posted: 1 decade ago Jan 20, 2011, 5:26 a.m. EST
Does the cross section of your waveguide include different subdomain with different material?
I would like to know how to do it respectively in version 4.0 and version 3.5a.
Did you do it similar to an example of "waveguide adapter" the model library by using a combined "Boundary model analysis " and "transient electromagnetic waves"?
I had a problem to define the boundary condition to be the eigenmode of mode solver.

I guess there are some other way to do it without combined module. Just extract the field of the eigenmode from the mode analysis using Matlab and import it to the transient module. I never try myself in this way. Did you also do it like this?

Does the cross section of your waveguide include different subdomain with different material? I would like to know how to do it respectively in version 4.0 and version 3.5a. Did you do it similar to an example of "waveguide adapter" the model library by using a combined "Boundary model analysis " and "transient electromagnetic waves"? I had a problem to define the boundary condition to be the eigenmode of mode solver. I guess there are some other way to do it without combined module. Just extract the field of the eigenmode from the mode analysis using Matlab and import it to the transient module. I never try myself in this way. Did you also do it like this?
Shakeeb Bin Hasan
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Posted: 1 decade ago Jan 21, 2011, 10:35 a.m. EST
Well, waveguide adapter model mode is not sufficient in transient analysis in which you have to define the field variables manually. But the beginning steps are the same, first mode analysis, then set manual value of propagation constant, and finally store solution in solver manager.

Now incorporating this result finally in the transient analysis module can be done rather easily by selecting scattering boundary condition. Doing mode analysis on the same boundary for the sake of simplicity, just write

Ex: real(tEx_rfwb*exp(i*w0*t))
Ey: real(tEy_rfwb*exp(i*w0*t))
Ez: real(En_rfwb*exp(i*w0*t))

Note that for above statements to be exact, x-y plane must be parallel to your boundary/waveguide cross-section. Then the z-component would be field component normal to the boundary as I have written. Also make sure that frequency w0 is defined already.

And I don't think it would be so straightforward to export solution from Matlab back to Comsol
Well, waveguide adapter model mode is not sufficient in transient analysis in which you have to define the field variables manually. But the beginning steps are the same, first mode analysis, then set manual value of propagation constant, and finally store solution in solver manager. Now incorporating this result finally in the transient analysis module can be done rather easily by selecting scattering boundary condition. Doing mode analysis on the same boundary for the sake of simplicity, just write Ex: real(tEx_rfwb*exp(i*w0*t)) Ey: real(tEy_rfwb*exp(i*w0*t)) Ez: real(En_rfwb*exp(i*w0*t)) Note that for above statements to be exact, x-y plane must be parallel to your boundary/waveguide cross-section. Then the z-component would be field component normal to the boundary as I have written. Also make sure that frequency w0 is defined already. And I don't think it would be so straightforward to export solution from Matlab back to Comsol
Muhammad Mohsin Rehman
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Posted: 1 decade ago Oct 16, 2011, 3:32 p.m. EDT
Hi,
I am usning COMSOL 4.0.I want to model electromagnetic waves model in 3D for heating purpose and see the effect on fluid.I can build the model by defining an Edge Current but I am not getting the temperature as a result instead I am getting the E-field distribution.
In addition, I want to define Port in the model (with Power Input and Electric field with propagation constant) instead of Edge Current (with current). I tried to define it but it gave me error, can you please help me out?


Many thanks in advance.
Hi, I am usning COMSOL 4.0.I want to model electromagnetic waves model in 3D for heating purpose and see the effect on fluid.I can build the model by defining an Edge Current but I am not getting the temperature as a result instead I am getting the E-field distribution. In addition, I want to define Port in the model (with Power Input and Electric field with propagation constant) instead of Edge Current (with current). I tried to define it but it gave me error, can you please help me out? Many thanks in advance.
donato conteduca
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Posted: 1 decade ago Jun 6, 2013, 8:26 a.m. EDT
Hi,
I have the same problem. I want to simulate a rib waveguide (as in the attached file) for a 3D model. The rib is a single TM mode with a neff=3.538. If I try to simulate the same structure in 3D model I can see higher order modes at least for a propagation of 50microns. I think that it depends on the imput field chosen for the structure. I consider a boundary scattering condition at the imput port with a plane wave with E0y = 1V/m. It needs more than 50microns to propagate only the first mode. I can't consider longer waveguides because the limited memory of my computer.
I want to use the modal distribution of the first TM mode obtained by 2D model as the imput of the 3D model. Is it possible? I'm using a version of Comsol 3.5 RF module.
I hope someone could help me.
Thanks!
Hi, I have the same problem. I want to simulate a rib waveguide (as in the attached file) for a 3D model. The rib is a single TM mode with a neff=3.538. If I try to simulate the same structure in 3D model I can see higher order modes at least for a propagation of 50microns. I think that it depends on the imput field chosen for the structure. I consider a boundary scattering condition at the imput port with a plane wave with E0y = 1V/m. It needs more than 50microns to propagate only the first mode. I can't consider longer waveguides because the limited memory of my computer. I want to use the modal distribution of the first TM mode obtained by 2D model as the imput of the 3D model. Is it possible? I'm using a version of Comsol 3.5 RF module. I hope someone could help me. Thanks!

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