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Multiple input ports in RF problems

Posted 12 déc. 2012, 02:46 UTC−5 RF & Microwave Engineering, Results & Visualization 8 Replies

Jisu Kim
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Hello,

I'am doing a simulation with RF module. It's about the mode analysis of a rectangular silicon waveguide.

There are two waveguides.

To propagate the monochromatic light of 1550nm (1.935e14 Hz ), I've put two extremity of the length of Silicon waveguide1 and waveguide2 as "excitation port1 and port2"(type "numeric", input power:1watt)

For the result of the "Boundary Mode Analysis", I can obtain the solutions of "effective mode index".
One problem is here. When I simulated by "Boundary Mode Analysis" , I couldn't get results from waveguide 1 and waveguide 2 simultaneously. So I restored just one boundary result from waveguide1 surface.
So as for the distribution of intensity of electric field, it's just result from waveguide1.

So my question is How can I get results from waveguide 1 and waveguide 2 simultaneously and
why I can't obtain a good distribution of electric field, because results seems abnormal theoretically (at least I think It will be symmetric.). Maybe there are some nessesary parameters that I haven't defined?

Waiting sincerely for your help, I'am really a "rookie" for COMSOL.

Best regards,
Jisu

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8 Replies Last Post 7 oct. 2013, 06:23 UTC−4
Alexander Kuznetsov
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Posted: 1 decade ago 12 déc. 2012, 17:01 UTC−5
As far as I know, you can't have multiple input ports.
As far as I know, you can't have multiple input ports.
Jisu Kim
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Posted: 1 decade ago 12 déc. 2012, 22:28 UTC−5

As far as I know, you can't have multiple input ports.


Thanks:)
Then is there any method using periodic boundary condition?

Left input and right input are same.
So I think I can get the result by the following steps...
First, I can get the propagation field with left surface boundary condition in the physics-periodic conditions-periodic boundary conditions. But there is nothing to change after this. (I expected I could find the same left input surface and right input surface.)
After then, by using periodic boundary condition I want to copy left simulation result to right.


Or I wonder another method. If I get get the propagation field with surface boundary condition for each, can I get the superposition between left and right propagation field?
[QUOTE] As far as I know, you can't have multiple input ports. [/QUOTE] Thanks:) Then is there any method using periodic boundary condition? Left input and right input are same. So I think I can get the result by the following steps... First, I can get the propagation field with left surface boundary condition in the physics-periodic conditions-periodic boundary conditions. But there is nothing to change after this. (I expected I could find the same left input surface and right input surface.) After then, by using periodic boundary condition I want to copy left simulation result to right. Or I wonder another method. If I get get the propagation field with surface boundary condition for each, can I get the superposition between left and right propagation field?
Alexander Kuznetsov
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Posted: 1 decade ago 13 déc. 2012, 20:12 UTC−5
If your structure is completely symmetric, you can model only half of it.

Another option is using scattering boundary condition to set up plane wave excitation.
If your structure is completely symmetric, you can model only half of it. Another option is using scattering boundary condition to set up plane wave excitation.
Robert Koslover Certified Consultant
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Posted: 1 decade ago 18 déc. 2012, 23:19 UTC−5
Actually, you CAN have multiple active input ports. I do it all the time and it is useful for computing how fields combine in microwave systems with more than one input. However, when you turn on more than one port at once, the S-matrix components will not be made available to you explicitly in the post-computation list of available quantities. Nevertheless, you can still construct the input and output powers, and you can certainly observe the phases as well, by means of defining integrals at each port of interest and/or plotting fields at points on the ports.

An example of a rather trivial case (combining 2 waveguide inputs in 2D) is presented in an animated .gif file (prepared with the old Comsol 3.5a) attached to this message. Just open and view it in your web browser to see the animation.
Actually, you CAN have multiple active input ports. I do it all the time and it is useful for computing how fields combine in microwave systems with more than one input. However, when you turn on more than one port at once, the S-matrix components will not be made available to you explicitly in the post-computation list of available quantities. Nevertheless, you can still construct the input and output powers, and you can certainly observe the phases as well, by means of defining integrals at each port of interest and/or plotting fields at points on the ports. An example of a rather trivial case (combining 2 waveguide inputs in 2D) is presented in an animated .gif file (prepared with the old Comsol 3.5a) attached to this message. Just open and view it in your web browser to see the animation.

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Alexander Kuznetsov
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Posted: 1 decade ago 19 déc. 2012, 13:15 UTC−5
Robert,

you are right. It does work. Thanks!
Robert, you are right. It does work. Thanks!
Hitesh Ghadiya
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Posted: 1 decade ago 20 déc. 2012, 00:51 UTC−5
I have corrugated waveguide structure I have define numeric port and I want to excite hybrid mode and symmetric boundary condition please help me. my mail id is hitesh3399@gmail.com
I have corrugated waveguide structure I have define numeric port and I want to excite hybrid mode and symmetric boundary condition please help me. my mail id is hitesh3399@gmail.com
Massimo Valerio Preite
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Posted: 1 decade ago 3 oct. 2013, 08:24 UTC−4
Hi.
I think that you should use a Boundary Mode Analysis for every port, not do all together (if I do so, I get a double solution for the effective mode index, probably COMSOL considers it like a coupled waveguide).
But then I have problems when I start the simulation, that aborts.
I attach the file, if this could be useful.
Hi. I think that you should use a Boundary Mode Analysis for every port, not do all together (if I do so, I get a double solution for the effective mode index, probably COMSOL considers it like a coupled waveguide). But then I have problems when I start the simulation, that aborts. I attach the file, if this could be useful.

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Massimo Valerio Preite
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Posted: 1 decade ago 7 oct. 2013, 06:23 UTC−4
I think I solved my and your problem : go to page 59-62 of the User's guide of the RF module.
I attached an image, because the manual isn't perfectly clear.
I think I solved my and your problem : go to page 59-62 of the User's guide of the RF module. I attached an image, because the manual isn't perfectly clear.

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