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induced charge density

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Hello everyone,

I am working with the RF module of the Comsol 4.3b version. I am trying to calculated the dipole moments (px, py, pz) of a split ring resonator (SRR) illuminated by a plane wave. For calculating the dipole moment in x, I need to do the following:

px = VolumeIntegral(r_x rho(r) dv)
here, rho(r) is the induced charge density and r_x is the x-coordinate of the split ring resonator.

I am trying to reproduce the results from a paper but I have the feeling that I am doing something wrong during the post processing, where I try to calculate the volume integral of current density norm.J as I do not know how I could get the following parameters from Comsol.
1. r_x, which is the x-coordinates inside the volume of the split-ring resonator only.
2. the induced charge density, rho(r)

I would be grateful if any soul out there has any idea how to approach this problem and could help me. Maybe Ivar? I have always found your insights very educational.

Thanks in advance :)

2 Replies Last Post 2016年4月29日 GMT-4 01:41
Robert Koslover Certified Consultant

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Posted: 8 years ago 2016年4月28日 GMT-4 23:01
If I understand you correctly, you seek to carry out an integral over one or more of your domains, of a computed quantity. If the "volume of the split-ring resonator only" corresponds to one or more such domains, you can do this in a variety of ways. Here's one approach.
In the Model Builder, under Component, right-click Definitions, select Probes --> Domain Probe. Choose probe type as Integral. And chose the domains you want (under selection) and the integrand you want where it says "Expression." Name and label the quantity whatever you want (e.g., MyDipoleMoment).
The rest of what you need to do should be relatively clear.

p.s. My answer applies to Comsol 5.x I apologize if it is different in 4.x
If I understand you correctly, you seek to carry out an integral over one or more of your domains, of a computed quantity. If the "volume of the split-ring resonator only" corresponds to one or more such domains, you can do this in a variety of ways. Here's one approach. In the Model Builder, under Component, right-click Definitions, select Probes --> Domain Probe. Choose probe type as Integral. And chose the domains you want (under selection) and the integrand you want where it says "Expression." Name and label the quantity whatever you want (e.g., MyDipoleMoment). The rest of what you need to do should be relatively clear. p.s. My answer applies to Comsol 5.x I apologize if it is different in 4.x

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Posted: 8 years ago 2016年4月29日 GMT-4 01:41
Hi ajeetraj,

I have some experiences in this problem. In RF module, it seems you can not get the induced charge density. Fortunately, you can get the induced current density. Then px = VolumeIntegral(r_x rho(r) dv) can be changed to px = VolumeIntegral(-1i/omega*Jx dv), where Jx is the x directional induced current density. Then you simply integrate the current density and get the results.

Regards,
Zhang
Hi ajeetraj, I have some experiences in this problem. In RF module, it seems you can not get the induced charge density. Fortunately, you can get the induced current density. Then px = VolumeIntegral(r_x rho(r) dv) can be changed to px = VolumeIntegral(-1i/omega*Jx dv), where Jx is the x directional induced current density. Then you simply integrate the current density and get the results. Regards, Zhang

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