how to excite a plane wave in comsol

May 5, 2011, 1:07 pm

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Guys:

Anybody know how to excite a plane wave excitation in COMSOL? Really appreciate it

Best
Meng

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Plane Wave in a Cube

January 26, 2012, 3:19 pm

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Hi All
I want to create a perfect plane wave in COMSOL.
I draw a cube and assign "plane wave radiation" to one side of it and "PML" to aother sides of cube. But instead of having "plane wave" I am getting "standing wave". It means I have a lot of radiation.
Can you help me how I can create a plane wave?

Best Way to Incident Electric Field

May 8, 2016, 6:01 pm

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I'm currently working on modeling a 2D gradient index metamaterial lens and studying the electric field intensity inside it. My geometry consists of vertical alternating layers of two different materials (Ag and Alumina) and I have to incident a plane wave from the top of the resulting rectangle and study the x-component of the resultant electric field intensity inside the lens. I've used port excitation, surface current, initial electric field at the upper boundary (which is also surrounded by a PML) but I can't seem to get my results. I'm 100% sure my geometry and physics are correct, so this definitely has something to do with my physics. Can anyone help me out with this? :)

Finite-width excitation source

May 12, 2016, 2:45 pm

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Dear users,

I would like to define a plane wave source which does not extend throughout the entire computational domain. In order to do it, I start with a square air box embedded into a larger square PML domain. Later, I define a plane wave source in the air, launch my wave and look at the E-field distribution. My wave is polarized out-of-plane.

For the plane wave, I would expect to have a wave which propagates parallel to the source and is getting absorbed by the PMLs. However, as you can see in the attached figure my field starts to expand to the left and right.

Is there a way to define it the way I want?

Best regards,
Andrzej

potential of an trapezoidal cross section cantilever

May 13, 2016, 8:09 am

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sir i got some problem regarding potential and i didn't even get any voltage i got 0 v in every frequency.
i m working in frequancy domain. i have completed all the work but i could not stimulate and i got some problem in evaluation of voltage . i have some pics of this simulation plz help me .

thnx
sahrukh khan

Optical absorption in MIM or MSM plasmonic structure

April 22, 2016, 6:28 am

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Hello,

I am studying the plasmonic effects on Metal-Si(SiO2)-Metal structure . I try to calculate the total optical absorption (1/m) on the surface of the structure using the Total Power Dissipation Density (emw.Qh). Did I use the correct option to get the logical result or should I use the other one?
However, emw.Qh gives both positive and negative value which I cannot understand. I thought that the total power dissipation density should be positive. Can you please comment on this and tell me where I am going wrong?

Best,
Hamed

Simulation Based on previous simulation results

May 18, 2016, 9:19 am

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I am working on an RF MEMS Switch, I used electromechanics physics and got its results. Now I want to simulate its RF Performance using Electromagnetic Waves, Frequency Domain physics, but based on the displacement I got from the electromechanics stationary simulation. How can I do that on COMSOL?
Thanks in advance.

Simulating 2D optical waveguide

February 24, 2010, 11:48 am

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Hi,

I am simulating a 2D optical waveguide for both TE and TM modes.

For TE waves I get reasonable result by setting the cladding core interface as perfect electric conductor.
I use excitation port with analytic mode and exist port also as analytic mode.

However, for TM modes I do not get a reasonable result (please see attached file).
I've switched the core-cladding interface to be perfect magnetic conductor.

Any comments will be helpful. Thanks.

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how to excite a plane wave in comsol

May 5, 2011, 8:07 am

≫ Next: Plane Wave in a Cube

≪ Previous: Simulating 2D optical waveguide

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Guys:

Anybody know how to excite a plane wave excitation in COMSOL? Really appreciate it

Best
Meng

Plane Wave in a Cube

January 26, 2012, 11:19 am

≫ Next: Convergence: when should I stop the model?

≪ Previous: how to excite a plane wave in comsol

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Hi All
I want to create a perfect plane wave in COMSOL.
I draw a cube and assign "plane wave radiation" to one side of it and "PML" to aother sides of cube. But instead of having "plane wave" I am getting "standing wave". It means I have a lot of radiation.
Can you help me how I can create a plane wave?

Convergence: when should I stop the model?

March 15, 2012, 11:55 am

≫ Next: Multi-Port S-parameter Calculation Simultaneously

≪ Previous: Plane Wave in a Cube

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Hi everyone

I have been working on models that take several days to solve. One of them is running at the moment, and I just have a general question.

When I look at the Convergence Plot 2, which is "Reciprocal of step size" vs "Time step", I can see the reciprocal of step size is between 10^5 and 10^6. It has been like this for several hours, and the progress value is at 2% without increasing.

I need results for this simulation by the beginning of next week. When do you know if you should stop the simulation or let it run and solve this convergence difficulty eventually? If I stop it, and the model could have advanced and solved, then I'll lose several hours of solving. But if I don't stop it, it might be at 2% for more than a day.

What should I do? What are the general guidelines on convergence?

Thank you so much!
Sylvana

Multi-Port S-parameter Calculation Simultaneously

October 22, 2015, 2:52 am

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Hi, Is Comsol able to calculate the S-parameters of multiports in s single computing ?

For example, if i want to know s11 s21, s12 and s22 , i have to first set port 1 on port 2 off and compute to get s11 and s21, then manually set port 1 off port 2 on to compute s12 and s22, it there an automatic way to do this ?

Thanks.
Cris

induced charge density

April 3, 2016, 11:33 pm

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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 :)

Why set the conductivity as zero?

April 26, 2016, 6:16 am

≫ Next: Patch antenna with a coat of Microwave absorber

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Hello everyone.

Here is another question about "scattering_nanosphere".
In this model, the conductivity of nanosphere (composed of Au) was set as 0. But its true value should be 45.6E6[S/m]. If we use it to replace the default one, then the result will be dramatically changed.

Please tell me which value should I use.
Thank you very much.

Patch antenna with a coat of Microwave absorber

April 26, 2016, 6:17 am

≫ Next: Mesh size and dimension of the structure

≪ Previous: Why set the conductivity as zero?

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Hi,
I am studying the improvement in absorption of radiation by microstrip patch antenna, which is coated with a layer of microwave absorber that I am going to develop.

How can I define the physics for this absorber?


Thanks in advance,

Best,
Karthik

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Mesh size and dimension of the structure

April 27, 2016, 5:14 am

≫ Next: time dependent EM-fields in cavity

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Hi Guys,

I am quite new in COMSOL, and I have three small questions about the setting of the mesh in ewfd, frequency domain study.

1. I found the results will be different if I used different size of the mesh, in this case, how could I value the setting of the mesh is suitable or not?

2. Another problem, the different dimension of my waveguide with same mesh size will also yield different results, how could I determine the right size of mesh if I change the length of my waveguide?

3. The distance between the light source and the boundary to my waveguide will also get different results, how could I choose the distance of the boundary to my waveguide.

Is there anyone have good suggestions? it would be very appreciated.

Chuan

time dependent EM-fields in cavity

April 28, 2016, 3:41 am

≫ Next: How to add a static current in Electromagnetic wave transient study

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Hi!
First of I apologize in advance for any stupid questions but I'm a new COMSOL user and would like to model the field inside a resonator. This is no problem in the frequency domain but when I try to do this in the time domain I run into problem. I want it in time domain as I would like to have particles interact with the field. I've tried a few different options but with no success.
I've tried a few different things, both feeding the cavity with a port, coupling the magnetic field in the resonator with a magnetic loop, doing an alternating voltage source to couple the E-field etc..None of these have worked so far and COMSOL doesn't seem to like very high frequencies when you're not in the frequency domain.
Can anyone point me in the right direction as to what physics/studies I should use?

TL;DR
What physics/studies should I use if I want to have particle-field interaction in a resonator?

I appreciate any answers

How to add a static current in Electromagnetic wave transient study

April 28, 2016, 5:11 am

≫ Next: Question about modeling propagating plane wave (wave optics)

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Hi,

I am working on a problem using electromagnetic waves transient module. I want to study the interaction between incident EM waves and an annulus conductor in which a static current is flowing on it.

It is easy to set up the incident EM waves using scattering boundary condition. My question is how can I establish the static current in the annulus conductor?

I can establish a static current in AC/DC module, such as the MEF study by putting a voltage difference on the two ends of the conductor. But it seems in electromagnetic waves transient study I can not define a voltage on the conductor end.

Any comment would be highly appreciated.

Zhang

Question about modeling propagating plane wave (wave optics)

May 1, 2016, 6:08 am

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Hi,
I am new to Comsol, so unfortunately I have little experience. I am trying to set up a very simple model in which I have a propagating plane wave in air, normally incident upon different materials with different geometries. It is to be a 2D model. Simply put: air medium, material (different types of plastic) with different geometries, then air. I am currently doing modeling in a ray tracing solver, but I wanted to compare the results with FDTD (patterned geometries are 2mm in size, corner cube reflectors). I want to know the reflectance / transmission of this plane wave as it interacts with these media. Plus I wanted the nice visualization of the plane wave reflecting for a presentation.

Here is a video (clip on the left), that I am trying to simulate. The plane wave can be a pulse, rather than continuous if that's easier to model.

www.youtube.com/watch?v=WRGfYqqjXDo

Any advice as far as the type of solver, setup, variables, etc. would be great. I feel like I should be able to do this! As it doesn't appear to be anything to complex other than a plane wave incident upon a surface!

Thanks,
Dan

serval questions of heat transfer in my project

May 2, 2016, 6:52 pm

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Hello
As the figure shows, I am using the fllowing models
(Heat Transfer>Conjugate Heat Transfer>Laminar Flow
Stationary situation
Surface-to-Surface Radiation), and try to find the temperature distribution of the air and the spheres.
I simplified the original object into two spheres,since its shape was very complex. The latter sphere has a boundary heat source.
I have some questions to solve:
1.Since the object was simplified, so the real convective area was changed, i need to modify the convective heat transfer coefficient, but I can't find the modify interface in comsol.
2.The Surface-to-Surface Radiation was considered, and the model is periodic, so I need to define the periodic boundaries as perfect mirrors (the default insulated conditions are just fine to the convective heat transfer and conduction heat transfer)， but I can't find the interface in comsol,too.
3. Since the original object was simplified into two spheres, so the heat conduction was incorrect，because the spheres are not contacted.I want to find the ht.gardT between the spheres and use the Fourier's law of heat conduction to define extra heat source on spheres, is it right?
thank you