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Oscillating electric dipole source Comsol RF module
Posted May 10, 2013, 8:17 a.m. EDT RF & Microwave Engineering Version 5.1 9 Replies
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Dear All,
I have question.
I do simulations of plasmonic gap nanoantennas, and I want to excite antenna with dipole source which is placed and oscillate in the middle of the gap.
I have questions.
First, as I know unit for electric dipole moment is Cm (coulomb * meter), and in Comsol there is electric CURRENT dipole moment and unit is Am (amper * meter). I will mark electric dipole moment as P, and electric CURRENT dipole moment as PI.
My first question is how to set up equation in of “electric point dipole”? Is that for example just 1 [mA], or cos(emw.omega*t) [mA], or something else?
My second question is what is relation between P and PI. Is that PI = P/t (time), or PI = dP/dt, or maybe PI = P*emw.omega??
My third question is about Mie scattering. I want to calculate scattering and absorption cross section and I need electric field to calculate that.
Do you maybe know relation between electric current dipole moment and electric field??
Thanks for every reply and suggestion.
I have question.
I do simulations of plasmonic gap nanoantennas, and I want to excite antenna with dipole source which is placed and oscillate in the middle of the gap.
I have questions.
First, as I know unit for electric dipole moment is Cm (coulomb * meter), and in Comsol there is electric CURRENT dipole moment and unit is Am (amper * meter). I will mark electric dipole moment as P, and electric CURRENT dipole moment as PI.
My first question is how to set up equation in of “electric point dipole”? Is that for example just 1 [mA], or cos(emw.omega*t) [mA], or something else?
My second question is what is relation between P and PI. Is that PI = P/t (time), or PI = dP/dt, or maybe PI = P*emw.omega??
My third question is about Mie scattering. I want to calculate scattering and absorption cross section and I need electric field to calculate that.
Do you maybe know relation between electric current dipole moment and electric field??
Thanks for every reply and suggestion.
9 Replies Last Post Jun 28, 2017, 10:47 a.m. EDT
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Posted:
1 decade ago
Nicola,
1. In RF for frequency domain analysis, type 1[m*A] to set up electric current dipole moment.
2. In your notation, “P” is electrostatic dipole moment, created by static charges of opposite sign separated by small distance. The relation is: PI=d/dt(P).
3.Use scattering field formulation for Mie scattering. To calculate scattering cross-section use the following expression:
sigma_sca=intop1_surf(-(emw.relPoavx*nx+emw.relPoavy*ny+emw.relPoavz*nz)
Absorption cross-section is calculated as:
sigma_abs=4*intop2_vol(emw.Qh)
3. There are several standard textbooks with equations for electric and magnetic fields due to electric dipole moment (for example: Balanis, Antenna Theory).
Regards,
Sergei
1. In RF for frequency domain analysis, type 1[m*A] to set up electric current dipole moment.
2. In your notation, “P” is electrostatic dipole moment, created by static charges of opposite sign separated by small distance. The relation is: PI=d/dt(P).
3.Use scattering field formulation for Mie scattering. To calculate scattering cross-section use the following expression:
sigma_sca=intop1_surf(-(emw.relPoavx*nx+emw.relPoavy*ny+emw.relPoavz*nz)
Absorption cross-section is calculated as:
sigma_abs=4*intop2_vol(emw.Qh)
3. There are several standard textbooks with equations for electric and magnetic fields due to electric dipole moment (for example: Balanis, Antenna Theory).
Regards,
Sergei
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Posted:
1 decade ago
Dear Mr Yushanov,
Thank you very much on reply.
It is very helpful.
But I still have one question.
If I put just 1[m*A] to set up electric current dipole moment, is it enough for dipole to get oscillating on some specific
wavelength (or frequency) which I put in parametric sweep.
So, I defined gold like realAu(emw.freq)-j*imagAu(emw.freq), I put wavelengths in parametric sweep from 500nm to 900 nm in 10nm steps, etc etc, and is it enough to put just electric point dipole with 1[m*A] in the gap for oscillating?
Thanks for reply again.
Nikola
Thank you very much on reply.
It is very helpful.
But I still have one question.
If I put just 1[m*A] to set up electric current dipole moment, is it enough for dipole to get oscillating on some specific
wavelength (or frequency) which I put in parametric sweep.
So, I defined gold like realAu(emw.freq)-j*imagAu(emw.freq), I put wavelengths in parametric sweep from 500nm to 900 nm in 10nm steps, etc etc, and is it enough to put just electric point dipole with 1[m*A] in the gap for oscillating?
Thanks for reply again.
Nikola
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Posted:
1 decade ago
Nikola,
In frequency domain, Maxwell equations are solved for field phasors. It means that you specify amplitude only in the Electric Point Dipole node: p=1[m*A]. Dipole will be oscillating with frequency emw.freq which you specify in parametric sweep.
If you are in time domain study, then you would specify electric dipole as p=1[m*A]*sin(omega*t).
Regards,
Sergei
In frequency domain, Maxwell equations are solved for field phasors. It means that you specify amplitude only in the Electric Point Dipole node: p=1[m*A]. Dipole will be oscillating with frequency emw.freq which you specify in parametric sweep.
If you are in time domain study, then you would specify electric dipole as p=1[m*A]*sin(omega*t).
Regards,
Sergei
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Posted:
1 decade ago
Dear Mr Yushanov,
Now is everything perfectly clear.
Thank you very much on both responses again.
Regards,
Nikola
Now is everything perfectly clear.
Thank you very much on both responses again.
Regards,
Nikola
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Posted:
9 years ago
Hi dear all,
How to add an oscillating in-plane electric dipole or an oscillating in-plane electric current source in 2D axisymmetric model with RF module?
First of all, there is no dipole node 2D axisymmetric formulation.
Under node ´points´, only ´line current (out-of-plane)´ is avaible. Unfortunately ´out-of-plane´ is what I don´t want.
Therefore, I tried to draw a line and applied ´surface current´ to the line. Now comes the question how to add an oscillating current.
Welcome any comments, hints and suggestions!
Thanks a lot!
Sarah
How to add an oscillating in-plane electric dipole or an oscillating in-plane electric current source in 2D axisymmetric model with RF module?
First of all, there is no dipole node 2D axisymmetric formulation.
Under node ´points´, only ´line current (out-of-plane)´ is avaible. Unfortunately ´out-of-plane´ is what I don´t want.
Therefore, I tried to draw a line and applied ´surface current´ to the line. Now comes the question how to add an oscillating current.
Welcome any comments, hints and suggestions!
Thanks a lot!
Sarah
Please login with a confirmed email address before reporting spam
Posted:
9 years ago
Hi dear all,
How to add an oscillating in-plane electric dipole or an oscillating in-plane electric current source in 2D axisymmetric model with RF module?
First of all, there is no dipole node 2D axisymmetric formulation.
Under node ´points´, only ´line current (out-of-plane)´ is avaible. Unfortunately ´out-of-plane´ is what I don´t want.
Therefore, I tried to draw a line and applied ´surface current´ to the line. Now comes the question how to add an oscillating current.
Welcome any comments, hints and suggestions!
Thanks a lot!
Sarah
I have the same problem. There's no such point dipole option in 2D axisymmetric RF module. What I'm using is also a surface current on a small piece of cylinder surface. Is this the best we can get here?
Any comment is appreciated!
--
Pu, ZHANG
DTU Fotonik
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Posted:
8 years ago
Sergei Yushanov：
“P” is electrostatic dipole moment, created by static charges of opposite sign separated by small distance. you say the relation is: PI=d/dt(P), as for two static charges, P is constant, so PI equals zero, I think P=q*exp(-i*omega*t), if so, PI=d/dt(P)=-i*q*omega*P, PI is related with omega, so if I set PI=1, and I sweep the omega, what's the meaning of "PI=1"?
“P” is electrostatic dipole moment, created by static charges of opposite sign separated by small distance. you say the relation is: PI=d/dt(P), as for two static charges, P is constant, so PI equals zero, I think P=q*exp(-i*omega*t), if so, PI=d/dt(P)=-i*q*omega*P, PI is related with omega, so if I set PI=1, and I sweep the omega, what's the meaning of "PI=1"?
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Posted:
8 years ago
Dear Mr Yushanov,
I hope every thing is fine with you.
I want to add 2 electric field sources around sphere. I used 2 electric point dipole in 3D around it on the same axis(z).
1- I determine 2 physical points and then linking between them and dipoles.
2- After that I choose the dipole moment option and I get 3 data entries for x, y and z, I know that these values determine the polarization of dipole moment and according to these values the power will be perpendicular to the polarization direction.
My first question is how can I determine the polarization direction and the physical points play a role in that.
The second: how could I convert from [A.m] unit to electron volt.
The attached pic is my structure and it is radio frequency model
Thanks in advance
I hope every thing is fine with you.
I want to add 2 electric field sources around sphere. I used 2 electric point dipole in 3D around it on the same axis(z).
1- I determine 2 physical points and then linking between them and dipoles.
2- After that I choose the dipole moment option and I get 3 data entries for x, y and z, I know that these values determine the polarization of dipole moment and according to these values the power will be perpendicular to the polarization direction.
My first question is how can I determine the polarization direction and the physical points play a role in that.
The second: how could I convert from [A.m] unit to electron volt.
The attached pic is my structure and it is radio frequency model
Thanks in advance
Attachments:
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Posted:
7 years ago
Hi everyone. I'm calculating the field distribution above a disk which is exited by a point dipole. My question is if I calculate the Electric Field, this is the total field, right? But I need to calculate the induced field 'in' the surface disk, without the point dipole field. It is posible to obtain that? how can I obtain it?
another question is how can I generate the charge density? Thanks
another question is how can I generate the charge density? Thanks