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Performing Parasitic Extraction

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Hello all,

I am graduate student at Texas A&M. I am new to COMSOL Multiphysics. I want to do some analysis on bus bars. I was wondering whether COMSOL Multiphysics supports extracting parasitic inductance and capacitance values for a given geometry.

If any one of you have done so, please let me know. I would really appreciate it if you can send me an email at pg978.iitkgp@gmail.com. I'll get back to you with additional questions.

If the customer/technical support team is reading this, can you please send me some more details on how can I obtain a student/academic version of Multiphysics.

Thanks and keep up the good work,
Pawan Garg


4 Replies Last Post Feb 21, 2012, 8:55 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Feb 20, 2012, 1:33 a.m. EST
Hi

here you are on the USER forum, we are all users (included the "moderators") so you should address such question (about licences" directly to support os to your local rep.

From what I can tell you can obtain most info on your models, inclusive stray capacitance and inductances, but again for the results to be "true" you need a good model, and (what I understand as) stray values often comes from the surrounding, not only the geometrical shape of your object

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Good luck
Ivar
Hi here you are on the USER forum, we are all users (included the "moderators") so you should address such question (about licences" directly to support os to your local rep. From what I can tell you can obtain most info on your models, inclusive stray capacitance and inductances, but again for the results to be "true" you need a good model, and (what I understand as) stray values often comes from the surrounding, not only the geometrical shape of your object -- Good luck Ivar

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Posted: 1 decade ago Feb 20, 2012, 11:12 a.m. EST
@Ivar: Thanks for the reply. I will contact support.

What if I want to explicitly know the value of stray inductances and capacitances (since I want to compare two configurations)? Can COMSOL Multiphysics do that? If yes, then can you point me to the correct module?

As you said, surroundings lead to stray impedances. However, geometry does play a role. For example, a flat plate will have a greater stray capacitance than a thin wire.

Best regards,
Pawan Garg
@Ivar: Thanks for the reply. I will contact support. What if I want to explicitly know the value of stray inductances and capacitances (since I want to compare two configurations)? Can COMSOL Multiphysics do that? If yes, then can you point me to the correct module? As you said, surroundings lead to stray impedances. However, geometry does play a role. For example, a flat plate will have a greater stray capacitance than a thin wire. Best regards, Pawan Garg

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Feb 20, 2012, 11:29 a.m. EST
Hi
that too indeed shape and environment. Y would expect that the ACDC module should do the job, it depends on geoemtry size and frequencies, at higher frequencies its the RF module you need. Check with support they are very helpful

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Good luck
Ivar
Hi that too indeed shape and environment. Y would expect that the ACDC module should do the job, it depends on geoemtry size and frequencies, at higher frequencies its the RF module you need. Check with support they are very helpful -- Good luck Ivar

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Posted: 1 decade ago Feb 21, 2012, 8:55 a.m. EST
IMO, COMSOL does not support extraction of strays in the way of being able to use it in a SPICE model. It will calculate all the parameters when it does a simulation but it would be up to you to be able to extract them yourself. COMSOL is not like HFSS or Sonnet where those programs do have spice model equivalents that they can generate.

What you can do is vary the conditions around the model and infer what the parasitics may be. It is not an easy road doing it this way. If it is a complex model, you have your work cut out for you.

You would most likely use AC/DC or RF modules. Note that as of right now there is no smith chart in comsol if you are looking to plot impedances that way. Lacking a smith chart does not help in extracting parasitics. You would end up calculating impedances or admittances directly from the solver.

Also note the even though comsol does have a "spice" simulator built in, it is fairly limited as of ver42a. LTspice is leaps and bounds ahead of it but you are using a FEA tool here. Its job is to get you physical data to help you analyze your structure where something like LTspice cannot do this.

IMO, COMSOL does not support extraction of strays in the way of being able to use it in a SPICE model. It will calculate all the parameters when it does a simulation but it would be up to you to be able to extract them yourself. COMSOL is not like HFSS or Sonnet where those programs do have spice model equivalents that they can generate. What you can do is vary the conditions around the model and infer what the parasitics may be. It is not an easy road doing it this way. If it is a complex model, you have your work cut out for you. You would most likely use AC/DC or RF modules. Note that as of right now there is no smith chart in comsol if you are looking to plot impedances that way. Lacking a smith chart does not help in extracting parasitics. You would end up calculating impedances or admittances directly from the solver. Also note the even though comsol does have a "spice" simulator built in, it is fairly limited as of ver42a. LTspice is leaps and bounds ahead of it but you are using a FEA tool here. Its job is to get you physical data to help you analyze your structure where something like LTspice cannot do this.

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