how to avoid reflection of TE wave in 2D in 4.4?

July 29, 2015, 9:43 am

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Hi,

I am working on a rectangular structure, where I've created a PML boundary condition on all the four sides of the rectangle by creating a layer on its all sides. Also, inside it I've created a square and done a mapping inside it. For the entire geometry, I've chosen air as the material. I've created an inside port, from which I've given TE wave excitation. After simulating, I could find that reflection from the mapped square domain. How to avoid reflection in this case?

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sweep + Values of variables not solved for

June 5, 2014, 2:30 pm

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I have a model which consists of two studies:
- Study 1 : Stationary with parametric sweep of parameter A
- Study 2 : Eigenmode, with parametric sweep of A, the result of Study 1 is the input for Study 2.

I was amusing that by using "Values of variables not solved for" I would get it work, but when I run a sweep of A I get always the same result for Step 2. I tried setting "Parameter value (A)" to "All" or "Automatic" but it seems that in both cases only the results of the last value of A from Step 1 is considered. If I set "Parameter value (A)" to a specific value and run the simulation for that value it works. My question is how I can access the results from Step 1 in a sweep?
Please advise.

Thanks
Mohsen

Simulating S and P Polarised EM Waves

August 3, 2015, 8:34 am

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I am trying to simulate a plane wave with either S or P polarisation incident upon a nanoparticle on a substrate at various angle of incidence (phi and theta). Following the Scatterer on a Substrate model I have managed to do this for a S polarised plane wave using the follwing port conditions:


INCIDENT
x| -sin(phi)*exp(-i*(kbx*x+kby*y))
y| cos(phi)*exp(-i*(kax*x+kay*y))
z| 0

Propogation| abs (kaz)

TRANSMITTED (Through Substrate)

x| -sin(phi)*exp(-i*(kbx*x+kby*y))
y| cos(phi)*exp(-i*(kbx*x+kby*y))
z| 0

Could somebody please explain how this is derived for the model as the pdf doesnt really explain this. Also how would i modify this to have P polarisation incident?

Many Thanks Josh

Lumped Capacitor in the RF Module, eigenfrequency

August 4, 2015, 4:43 am

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Hello all,

I'm using 4.4, and I realize it is impossible to add Lumped Capacitor and Lumped Inductor in RF Module Eigenfrequency study.

(but lumped elements with Z value is possible, and Lumped Capacitor or Lumped Inductor is possible for frequency study)

I think it is because Comsol is looking for a frequency, so if you only give capacitance, how it can calculate impedance lol. My current solution is hand calculate a Z value with approximated frequency and input this Z value, then look for eigenfrequency.

Then my question is, how to use lumped element with capacitor type in Comsol? Is 5.1 or 5.0 can fix this problem? Or any other brilliant solutions?

Regards,
Jared

Superconductor in RF module

August 5, 2015, 1:28 pm

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Hi all,

Is there a simple way to define a superconductor material and directly assign it to a boundary in emw simulations?

I saw some papers using PEC instead of a real superconductor but I'm not sure if there's any significant difference. I will simulate both in eigenfrequency and frequency domin.

If the easy way (just define a supercondutor material and assign to a boudry or just use PEC) is impossible or mot accurate, is there a hard way, maybe by add other physics?

Best,
Hengjiang

Plasmonic Wire Grating Not Working

November 22, 2011, 12:00 am

≫ Next: frequency domain study of a heat transfer model

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I followed the steps in the plasmonic wire grating tutorial for COMSOL 4.2. When I try to compute the results it says it has encountered a problem with stationary solver 1(sol1/s1) and Failed to evaluate variable jacobian. I took a look at my variable files and comsol says that emw.k0 is an unknown variable. The tutorial says to use this variable to define ka. How do i get comsol to recognize what emw.k0 is. Also what is emw.k0, the tutorial didn't explain what it was.

frequency domain study of a heat transfer model

August 6, 2015, 7:16 am

≫ Next: "error: solnum out of range" RF module, mode analysis

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Hi everyone.

I am new to comsol, it would be appreciated if someone helps me. I want a frequency domain study analysis of a heat transfer model. Is there an easy way in comsol to do this.?

Basically I have a dielectric resonator antenna DRA, I perform thermal simulation using Heat transfer model analysis to analyze the effect of ambient temperature on the surface of DRA over certain period of time. Now I want to saw the radiation pattern and S11 parameters of antenna, that what is the effect of temperature on the radiation pattern of antenna.?

Thanks in advance.

"error: solnum out of range" RF module, mode analysis

August 9, 2015, 4:21 am

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Hi,

I am doing a mode analysis for a plasmonic waveguide, now, when i am trying to open the file, the whole loading process of opening the model is done, then a message appears that tell me that "solnum is out of range", and the model doesn't open, and I need the results in this file. Thanks in advance.

Best Regards,
Abdalrahman

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Convergence problem in time dependent solver

September 26, 2011, 12:58 pm

≫ Next: Negative transmittance in comsol

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Hi,

I'm getting this error when running a time dependent simulation of laminar flow in a micro channel. What I want to do is change the input flow on one arm of a y-channel and follow the response in time. Anyway it's this error:

Repeated error test failures. May have reached a singularity.
Time : 0
Last time step is not converged.

Now I've seen people with similar problems where it is due to too large a change in the time dependent parameter but I don't see how this is the case here. I am simulating for t=0 with the stationary solver first which is giving the correct result and at t=0 for the time dependent solver the boundary conditions should be exactly the same. I've tried several different time steps and different arrangements for the step function I'm using to change the flow. If it failed as the flow changed I'd think there was a point to the error but this doesn't make sense to me. Anyone have any ideas?

Negative transmittance in comsol

August 10, 2015, 5:47 am

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Hello everyone

I am simulating a model for periodic silver sphere for in-plane and out-plane polarization. But when i am plotting the transmittance in case of in-polarization with angle of incident 50 deg then it gives me transmittance value greater than 1 while it is giving the correct value of out-plane polarization even also it is giving correct value of transmittance for angle less than 50 deg in in plane also.

I don't know why it is happening ?
If anyone have any suggestion please help me.

Thanks

Slit conditions error

August 11, 2015, 1:54 am

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Hi Everyone.

I am working on Dielectric Resonator Antenna in Comsol 4.4. When I complete my design and try to compute, it always has an error.

"The slit condition should be applied only on an interior boundary or the port should be placed on an exterior boundary."

What is this slit conditions in Comsol.? Can anyone help me how to solve this problem. Its urgent. Thanks in advance.

Convergence problem in time dependent solver

September 26, 2011, 6:58 am

≫ Next: Plasmonic Wire Grating Not Working

≪ Previous: Slit conditions error

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Hi,

I'm getting this error when running a time dependent simulation of laminar flow in a micro channel. What I want to do is change the input flow on one arm of a y-channel and follow the response in time. Anyway it's this error:

Repeated error test failures. May have reached a singularity.
Time : 0
Last time step is not converged.

Now I've seen people with similar problems where it is due to too large a change in the time dependent parameter but I don't see how this is the case here. I am simulating for t=0 with the stationary solver first which is giving the correct result and at t=0 for the time dependent solver the boundary conditions should be exactly the same. I've tried several different time steps and different arrangements for the step function I'm using to change the flow. If it failed as the flow changed I'd think there was a point to the error but this doesn't make sense to me. Anyone have any ideas?

Plasmonic Wire Grating Not Working

November 21, 2011, 6:00 pm

≫ Next: sweep + Values of variables not solved for

≪ Previous: Convergence problem in time dependent solver

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I followed the steps in the plasmonic wire grating tutorial for COMSOL 4.2. When I try to compute the results it says it has encountered a problem with stationary solver 1(sol1/s1) and Failed to evaluate variable jacobian. I took a look at my variable files and comsol says that emw.k0 is an unknown variable. The tutorial says to use this variable to define ka. How do i get comsol to recognize what emw.k0 is. Also what is emw.k0, the tutorial didn't explain what it was.

sweep + Values of variables not solved for

June 5, 2014, 8:30 am

≫ Next: How to draw a periodic waveguide?

≪ Previous: Plasmonic Wire Grating Not Working

$

0

0

I have a model which consists of two studies:
- Study 1 : Stationary with parametric sweep of parameter A
- Study 2 : Eigenmode, with parametric sweep of A, the result of Study 1 is the input for Study 2.

I was amusing that by using "Values of variables not solved for" I would get it work, but when I run a sweep of A I get always the same result for Step 2. I tried setting "Parameter value (A)" to "All" or "Automatic" but it seems that in both cases only the results of the last value of A from Step 1 is considered. If I set "Parameter value (A)" to a specific value and run the simulation for that value it works. My question is how I can access the results from Step 1 in a sweep?
Please advise.

Thanks
Mohsen

How to draw a periodic waveguide?

April 13, 2015, 10:06 pm

≫ Next: Is there a variable Ex in Electromagnetic Waves module?

≪ Previous: sweep + Values of variables not solved for

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Hi all,
I have a simple question towards for geometry for which I didn't a lot of search but still confused.
So how do you draw a periodic waveguide that has a simple mathematical expression in 3D?
For example, in this blog of corrugated waveguide
www.comsol.com/blogs/computing...mpedance-corrugated-waveguide/
I was looking for some "nonlinear extrusion", but didn't see it.
It would be so nice of you if you could give me a quick answer even with one keyword.

Best,
Cathy

P.S. I think this would be less version related, but I'm using 4.3a

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Is there a variable Ex in Electromagnetic Waves module?

July 12, 2015, 3:22 pm

≫ Next: Impedance in RF module & Transmission Line module

≪ Previous: How to draw a periodic waveguide?

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Dear all,

By the question in the title, I mean a variable named exactly as Ex, without emw. prefix. Is it an internal variable?

I input such a variable by mistake in a model. COMSOL didn't report an error, but the results were totally wrong. After changing to emw.Ex, the results make much more sense.

Thanks!
--
Pu, ZHANG
DTU Fotonik

Impedance in RF module & Transmission Line module

July 15, 2015, 10:37 pm

≫ Next: Modeling of resonant absorbtion

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Hi !

I am currently on a project. I am trying to model human liver and the reaction of tissues due to the heat. There are models already set up in COMSOL. They are called "tumor_ablation" and "microwave_cancer_therapy" and they are placed in the " Heat transfert module" library.

It's the exact thing that I want but I would like to upgrade it.

I have an electrical modeling of liver, that let me know the impedance in function of the frequency.

So my objective is to use the geometric of the "tumor_ablation" model, using the "microwave_cancer_therapy" physics (especially the RF module), changing the impedance of tissues by my function.

1) Is it possible ? (I mean to change the impedance by my function )

1 bis) Is it possible using the Transmission Line module?

2) If yes , how ?

Thanks for your consideration, it's the first time that I meet this software so I just know few things that I have learned watching COMSOL videos.

Modeling of resonant absorbtion

July 22, 2015, 4:03 am

≫ Next: How to set up the port?

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Hello,

I am wondering if it is possible for COMSOL to model the resonant absorption of protons in a static magnetic field.

For example, if I had a 1T field along the Z-axis with a water phantom inside, I would expect to see resonant absorption if I applied a 42.58 MHz RF pulse at 90 degrees to the Z-axis.

I am currently working on modeling this and would just like to know if such a thing is possible.

Thank you

How to set up the port?

July 22, 2015, 10:05 pm

≫ Next: microfluidic + external force field (optical force)

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Dear all,

I use RF module constructing 2 models, which have same structures except the length. The input power and other parameters are also the same. But after simulation, the power at the incident port of both models are not equal. I want them to have a same value in order to compare the wave and study the dissipate power along distance. I already use a scattering BC. The characteristic are similar but still not equal. So, I wonder that is there any way to set up the structure to have a same input power after the simulation?

Thank you in advance

microfluidic + external force field (optical force)

July 23, 2015, 6:04 am

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≪ Previous: How to set up the port?

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Hi, everybody
I am a new user and just learned the tutorial of particle separation in microfluidics (www.comsol.com/model/red-blood-cell-separation-17013).

I am working on a problems that how the particle motion will be deviated by an external force field, may I know how to do the modification from that tutorial?

This force is generated from an external electromagnetic wave, so called optical force. If I want to further include the RF module and do the whole simulation, are there any samples I can follow please? thank you!