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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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How accurate is Comsol compared to FDTD

Posted Jun 25, 2014, 10:33 a.m. EDT RF & Microwave Engineering, Geometry, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 3.5a 1 Reply

Naema Othman
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Hi:
I am a comsol user. My supervisor asked me to re simulate a design that was done in FDTD using Comsol.
The problem I got is that my solution was not the same as the FDTD solution!!. I am sure I have no error but I have to check with you (comsol community) in case someone can help me figure out what is going on.
I solved for RF (MODE ANALYSIS) and the effective index I got was 3.81. However, the FDTD solution was 3.88.
The shape of the mode I got with Comsol is clearly different from the one done with FDTD.

Any help?. Should I give you the two files to see them?
1 Reply Last Post Jun 25, 2014, 11:13 a.m. EDT
Pu Zhang
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Posted: 1 decade ago Jun 25, 2014, 11:13 a.m. EDT
According to my very limited experience with COMSOL's mode solver, good accuracy requires very fine mesh. So probably you can try to do some convergence study with mesh size.

As for mode profile, if you have degenerate modes, the pattern has certain arbitrariness. Linear combinations of them are also eigenmodes. You could check this.
According to my very limited experience with COMSOL's mode solver, good accuracy requires very fine mesh. So probably you can try to do some convergence study with mesh size. As for mode profile, if you have degenerate modes, the pattern has certain arbitrariness. Linear combinations of them are also eigenmodes. You could check this.

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