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Automatically rejecting certain eigenmodes

Posted 08.10.2011, 15:04 GMT-4 RF & Microwave Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.2 4 Replies

dnh37
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Hi,

I regularly simulate optical eigenmodes using comsol 4.2 rf mode solver. I set the outer boundaries to be perfect electric conductor, put a waveguide somewhere in the middle, and solve for the mode in the waveguide. However the problems are often more complex, but this is just a simple example of what I am doing.

When I solve for modes I get a bunch of modes, not all of which are physical. It is immediately obvious to a human that the modes that do not go to zero everywhere on the outer boundary are not physical. For complicated simulations however I find myself hunting through many modes, sometimes hundreds, to find the correct physical one.

Is there some feature where I can filter the modes, so, say, I reject all the results where the field is not zero or nearly zero on the outer boundaries? This would be a GREAT feature to have.

Thanks
David
4 Replies Last Post 11.10.2011, 08:46 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 11.10.2011, 08:05 GMT-4
Hi

in the modal solver you have a setting to define "modes around", this puts roughly a "notch filter" around the node number.

--
Good luck
Ivar
Hi in the modal solver you have a setting to define "modes around", this puts roughly a "notch filter" around the node number. -- Good luck Ivar
dnh37
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Posted: 1 decade ago 11.10.2011, 08:40 GMT-4
OK thanks Ivar. However I'd like to filter the *nonphysical* ones out (by some metric defined by me -- in this case, those that don't go to zero or near zero on the boundaries) rather than just filter by frequency.

So this requires some kind of logic to be set up, to test each mode after it's found and see if it conforms to the rule I set (rule = zero on the boundaries)

So I guess there is no way to do this? I think it'd be a really helpful feature..

Thanks
OK thanks Ivar. However I'd like to filter the *nonphysical* ones out (by some metric defined by me -- in this case, those that don't go to zero or near zero on the boundaries) rather than just filter by frequency. So this requires some kind of logic to be set up, to test each mode after it's found and see if it conforms to the rule I set (rule = zero on the boundaries) So I guess there is no way to do this? I think it'd be a really helpful feature.. Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 11.10.2011, 08:45 GMT-4
Hi

no I'm not aware of such conditions on the modes, I would like to have it for model reduction in structural, but here too its all or none ;) Try it out with support, there might be something coming, I suppose the next release is for tomorrow at the Boston conference (hope so, I'm in EU so I need to still wait a couple of weeks ;)

--
Good luck
Ivar
Hi no I'm not aware of such conditions on the modes, I would like to have it for model reduction in structural, but here too its all or none ;) Try it out with support, there might be something coming, I suppose the next release is for tomorrow at the Boston conference (hope so, I'm in EU so I need to still wait a couple of weeks ;) -- Good luck Ivar
dnh37
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Posted: 1 decade ago 11.10.2011, 08:46 GMT-4
OK thanks, I will email the suggestion to support.
OK thanks, I will email the suggestion to support.

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