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CPW with Resonator
Posted 6 feb 2014, 08:58 GMT-5 Low-Frequency Electromagnetics, RF & Microwave Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions 2 Replies
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Dear Community,
I've been trying to set up a model of CPW with a split-ring resonator (SRR) for quite a while now. Sadly, without much success. I've also tried to alter a couple of the related problems within the model library. But did also not get very far.
The model:
A CPW consisting of a signal line (S) and to adjacent ground lines (G) is supposed to be fed with an alternating current with frequencies within the GHz region. The ground lines run in parallel. In order to locally increase the current density a narrowing region is introduced where the width of the signal line and the ground lines as well as the width of the gap between them is decreased. Also, one of the ground lines is opened at the narrowing region to leave space for the SRR. The produced electromagnetic field should induce an alternating current into the SRR. The SRR itself creates an electromagnetic field which interferes with the one created by the CPW. If the phase difference of both ACs equals Pi, the interference reduces the the field to a minimum. This should be visible within a frequency sweep. The resulting graph should display a S21 parameter with a dip at the resonance frequency.
I was able to set up a model with the required geometry. But the results are not as expected and cannot be physical correct. Plus I cannot visualize the surface current of the signal line and SSR. There seems to be a field that couples with the SSR but it is very weak and does not influence the S21 output.
The setup is similar to a simulation discribed in APPLIED PHYSICS LETTERS 92, 254103 (2008) (DOI: 10.1063/1.2946656). I even tried to recreate their simulation in COMSOL, but it did not work. I attached on of my attempts.
I would be very greatful if somebody could help me out here.
Best,
Lennart
I've been trying to set up a model of CPW with a split-ring resonator (SRR) for quite a while now. Sadly, without much success. I've also tried to alter a couple of the related problems within the model library. But did also not get very far.
The model:
A CPW consisting of a signal line (S) and to adjacent ground lines (G) is supposed to be fed with an alternating current with frequencies within the GHz region. The ground lines run in parallel. In order to locally increase the current density a narrowing region is introduced where the width of the signal line and the ground lines as well as the width of the gap between them is decreased. Also, one of the ground lines is opened at the narrowing region to leave space for the SRR. The produced electromagnetic field should induce an alternating current into the SRR. The SRR itself creates an electromagnetic field which interferes with the one created by the CPW. If the phase difference of both ACs equals Pi, the interference reduces the the field to a minimum. This should be visible within a frequency sweep. The resulting graph should display a S21 parameter with a dip at the resonance frequency.
I was able to set up a model with the required geometry. But the results are not as expected and cannot be physical correct. Plus I cannot visualize the surface current of the signal line and SSR. There seems to be a field that couples with the SSR but it is very weak and does not influence the S21 output.
The setup is similar to a simulation discribed in APPLIED PHYSICS LETTERS 92, 254103 (2008) (DOI: 10.1063/1.2946656). I even tried to recreate their simulation in COMSOL, but it did not work. I attached on of my attempts.
I would be very greatful if somebody could help me out here.
Best,
Lennart
Attachments:
2 Replies Last Post 7 feb 2014, 04:26 GMT-5
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Posted:
1 decade ago
Lennart,
I've taken a brief look at the model you attached, and a few thoughts come to mind:
1) The mesh in the attached model is much too coarse. CPWs have very strong field gradients, and the mesh needs to be sufficiently fine to properly capture them.
2) The scattering BC on the back side of the substrate is probably going to have a non-physical effect on the solution. If there is air on the back side, I'd recommend including an air domain between the substrate and the scattering BC.
3) Some types of planar structures require the metallization thickness to be explicitly modeled to correctly capture the behavior of the structure, but I am not sure whether that is true in your case.
--
Luke Gritter
AltaSim Technologies
I've taken a brief look at the model you attached, and a few thoughts come to mind:
1) The mesh in the attached model is much too coarse. CPWs have very strong field gradients, and the mesh needs to be sufficiently fine to properly capture them.
2) The scattering BC on the back side of the substrate is probably going to have a non-physical effect on the solution. If there is air on the back side, I'd recommend including an air domain between the substrate and the scattering BC.
3) Some types of planar structures require the metallization thickness to be explicitly modeled to correctly capture the behavior of the structure, but I am not sure whether that is true in your case.
--
Luke Gritter
AltaSim Technologies
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Posted:
1 decade ago
Thank you very much for the quick reply, Luke. The mesh has definitely a strong influence on the simulation. But it wouldn't solve the problem, that I don't have any alternating surface currents at all. I have a feeling, that the RF module is missing some key aspects.
I've also tried to add an air domain underneath the substrate.
Next step is a finite thickness of the metallization...
Best,
Lennart
I've also tried to add an air domain underneath the substrate.
Next step is a finite thickness of the metallization...
Best,
Lennart