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v4 RF what is the way to find Dipole field pattern as doughnut shape

Posted 17.10.2010, 13:47 GMT-4 RF & Microwave Engineering Version 4.1 18 Replies

Irfan
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Hi,

I drove a dipole (1/2 wavelength) and found its E norm farfield, on a sphere. This however doest not matches the standard presentation of 3d dipole pattern that is close to doughnut shape .

How can I get it and other 2d patterns from different cuts of the same doughnut shape, I am looking for.
I am also attaching the model.

Thanks

Irfan
18 Replies Last Post 07.09.2011, 04:38 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18.10.2010, 02:53 GMT-4
Hi

I do not fully catch your model, you have only one input port, no ground, and for me a dipole has (as its name says) two poles, but I could have missed something too

--
Good luck
Ivar
Hi I do not fully catch your model, you have only one input port, no ground, and for me a dipole has (as its name says) two poles, but I could have missed something too -- Good luck Ivar
Irfan
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Posted: 1 decade ago 18.10.2010, 05:49 GMT-4
Hi,

I only worked out how to implement core ideas of old tutorial, in V4. A lumped port is equivalent to a circuit or cable, that I used. I do not think that a separate ground connection is needed to drive a dipole in COMSOL.
Actually I want to know how to plot farfield pattern, without requesting over the sphere, the doughnut is an example of dipole. you may give any other antenna example, that shows pattern in conventional / physical way
I need both 3D and 2D plots.

Thanks

Irfan
Hi, I only worked out how to implement core ideas of old tutorial, in V4. A lumped port is equivalent to a circuit or cable, that I used. I do not think that a separate ground connection is needed to drive a dipole in COMSOL. Actually I want to know how to plot farfield pattern, without requesting over the sphere, the doughnut is an example of dipole. you may give any other antenna example, that shows pattern in conventional / physical way I need both 3D and 2D plots. Thanks Irfan
Khalid Alharbi
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Posted: 1 decade ago 04.07.2011, 08:46 GMT-4
Hi,

I have the same problem. How to plot the radiation pattern?
Any hint???

Cheers,
Khalid
Hi, I have the same problem. How to plot the radiation pattern? Any hint??? Cheers, Khalid
Edgar Kaiser
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Posted: 1 decade ago 04.07.2011, 09:01 GMT-4
Hi,

you must add a Far Field Calculations Node under the electromagnetic waves (emw) node. This will make the far field variables available for postprocessing.

I advise only to use 2D plots, e.g. for azimuth and elevation patterns. 3D plots take ages to calculate, on my machine they take more time than solving the model.

Cheers
Edgar

Hi, you must add a Far Field Calculations Node under the electromagnetic waves (emw) node. This will make the far field variables available for postprocessing. I advise only to use 2D plots, e.g. for azimuth and elevation patterns. 3D plots take ages to calculate, on my machine they take more time than solving the model. Cheers Edgar
Khalid Alharbi
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Posted: 1 decade ago 04.07.2011, 09:14 GMT-4
Hi Edgar,

I downloaded your model ( dipole 3D) . You added two slices. Are they the 2D Plots that you mean?
If so, how can i calculate the gain and the 3-db beamwidth of the same model?
It will help much .

Cheers,
Khalid
Hi Edgar, I downloaded your model ( dipole 3D) . You added two slices. Are they the 2D Plots that you mean? If so, how can i calculate the gain and the 3-db beamwidth of the same model? It will help much . Cheers, Khalid
Edgar Kaiser
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Posted: 1 decade ago 04.07.2011, 09:36 GMT-4
No, that is an earlier model. I am attaching the model of a 4 element yagi. Look at the polar plots. I needed to clear the solution, otherwise the model would be too big to upload.

Cheers
Edgar
No, that is an earlier model. I am attaching the model of a 4 element yagi. Look at the polar plots. I needed to clear the solution, otherwise the model would be too big to upload. Cheers Edgar
Khalid Alharbi
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Posted: 1 decade ago 04.07.2011, 09:48 GMT-4
Hi Edgar,

I can't open the file. This message is shown:
" COMSOL Error
File Contains no model"
I am using version 4.0.0.925

Cheers
Khalid
Hi Edgar, I can't open the file. This message is shown: " COMSOL Error File Contains no model" I am using version 4.0.0.925 Cheers Khalid
Edgar Kaiser
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Posted: 1 decade ago 04.07.2011, 09:58 GMT-4
It is a version 4.1 model.
It is a version 4.1 model.
Khalid Alharbi
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Posted: 1 decade ago 06.07.2011, 20:42 GMT-4
Hi Edgar,

This model is very useful. And the polar plot is very fast.
Could you explain why you used the expressions in the angle data section. And should i use the same expressions for any model when ploting the far field pattern?

Cheers,
Khalid
Hi Edgar, This model is very useful. And the polar plot is very fast. Could you explain why you used the expressions in the angle data section. And should i use the same expressions for any model when ploting the far field pattern? Cheers, Khalid
Edgar Kaiser
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Posted: 1 decade ago 07.07.2011, 05:08 GMT-4
Khalid,

the expression gives you the angle in the polar plot and allows to rotate the pattern. Arc length works as well but the results are rotated by 90 degrees. I wanted the main lobe point to 0 degrees.

Just a matter of taste (or definition).

Cheers
Edgar
Khalid, the expression gives you the angle in the polar plot and allows to rotate the pattern. Arc length works as well but the results are rotated by 90 degrees. I wanted the main lobe point to 0 degrees. Just a matter of taste (or definition). Cheers Edgar
Glenston Miranda
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Posted: 1 decade ago 22.08.2011, 13:26 GMT-4

No, that is an earlier model. I am attaching the model of a 4 element yagi. Look at the polar plots. I needed to clear the solution, otherwise the model would be too big to upload.

Cheers
Edgar


Hi Edgar,

I've just started working on COMSOL , and i needed a little help to understand your model .
It would really help me a lot if the doubts are clarified.

1. In the type field for scattering boundary condition you have used plane wave but for the PML you have used Spherical.Shouldn't the type for the scattering field condition be spherical like the PML?

2.Is it necessary to have scattering boundary condition when there's a PML condition, as the primary purpose of using scattering boundary condition is for absorption of incoming waves which the PML region does effectively.

3. What's the basis for using Zref=28ohm , and in the impedance boundary condition the value 3.774e7 is based on which material.

Lastly will a 64 bit windows OS with 8 gb ram not be sufficient to run the 3D radiation pattern? How long might it take approximately ?

Thank a Lot in advance , your model and comments have helped me tremendously!
Looking forward to hear for your reply.

Regards
Glenston
[QUOTE] No, that is an earlier model. I am attaching the model of a 4 element yagi. Look at the polar plots. I needed to clear the solution, otherwise the model would be too big to upload. Cheers Edgar [/QUOTE] Hi Edgar, I've just started working on COMSOL , and i needed a little help to understand your model . It would really help me a lot if the doubts are clarified. 1. In the type field for scattering boundary condition you have used plane wave but for the PML you have used Spherical.Shouldn't the type for the scattering field condition be spherical like the PML? 2.Is it necessary to have scattering boundary condition when there's a PML condition, as the primary purpose of using scattering boundary condition is for absorption of incoming waves which the PML region does effectively. 3. What's the basis for using Zref=28ohm , and in the impedance boundary condition the value 3.774e7 is based on which material. Lastly will a 64 bit windows OS with 8 gb ram not be sufficient to run the 3D radiation pattern? How long might it take approximately ? Thank a Lot in advance , your model and comments have helped me tremendously! Looking forward to hear for your reply. Regards Glenston
Edgar Kaiser
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Posted: 1 decade ago 23.08.2011, 06:37 GMT-4
Hi Glenston,

this model was a first attempt to try far field calculations in RF. I haven't been doing much more about it recently and there may be some inconstistencies. But I will try to answer as far as possible:

1. and 2. I think you are right, the PML should be sufficient.

3. The 28 Ohms is a measured value from a realized yagi antenna of this kind and also from EZNEC, that is a momentum based antenna simulator.

4. The impedance boundary value may be the conductivity of aluminium or copper, not sure about that.

I ran the model on a 64 bit windows 7 machine with 12 GB RAM. For one frequency it may take some 10-15 minutes to solve and 20-30 minutes to calculate the far field in 3D. The 2D patterns are much quicker. I think 8 GB should be sufficient too. For a first test, disable the parametric sweep and solve it for one frequency.

Regards
Edgar

Hi Glenston, this model was a first attempt to try far field calculations in RF. I haven't been doing much more about it recently and there may be some inconstistencies. But I will try to answer as far as possible: 1. and 2. I think you are right, the PML should be sufficient. 3. The 28 Ohms is a measured value from a realized yagi antenna of this kind and also from EZNEC, that is a momentum based antenna simulator. 4. The impedance boundary value may be the conductivity of aluminium or copper, not sure about that. I ran the model on a 64 bit windows 7 machine with 12 GB RAM. For one frequency it may take some 10-15 minutes to solve and 20-30 minutes to calculate the far field in 3D. The 2D patterns are much quicker. I think 8 GB should be sufficient too. For a first test, disable the parametric sweep and solve it for one frequency. Regards Edgar
Glenston Miranda
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Posted: 1 decade ago 23.08.2011, 06:56 GMT-4
Hi Edgar,

Thanks a lot for your patience and reply .
It will help me a lot.

Another totally different question.
Ive built a parametric curve in 2D geometry with specifications as follows.

parameter name :s
range from 0-20.
x exp: (125s+700)*cos(s)
y exp: (125s+700)*sin(s)

This gives me a 2 arm spiral around (0,0) with negligible width.
I want to have a finite width to this spiral in 2D.

Do you know how i can do that?
Thanks a lot again for your time and effort!

Regards
Glenston

Hi Edgar, Thanks a lot for your patience and reply . It will help me a lot. Another totally different question. Ive built a parametric curve in 2D geometry with specifications as follows. parameter name :s range from 0-20. x exp: (125s+700)*cos(s) y exp: (125s+700)*sin(s) This gives me a 2 arm spiral around (0,0) with negligible width. I want to have a finite width to this spiral in 2D. Do you know how i can do that? Thanks a lot again for your time and effort! Regards Glenston
Edgar Kaiser
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Posted: 1 decade ago 23.08.2011, 08:35 GMT-4
Hi Glenston,

I am not completely sure what you mean. A curve doesn't have a width.
If you want to create a spiral geometry (a spiral antenna?) you might consider two spirals that are rotated a bit with respect to each other and use the curves as boundaries for the spiral domain.

Regards
Edgar
Hi Glenston, I am not completely sure what you mean. A curve doesn't have a width. If you want to create a spiral geometry (a spiral antenna?) you might consider two spirals that are rotated a bit with respect to each other and use the curves as boundaries for the spiral domain. Regards Edgar
Glenston Miranda
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Posted: 1 decade ago 23.08.2011, 09:33 GMT-4

Hi Glenston,

I am not completely sure what you mean. A curve doesn't have a width.
If you want to create a spiral geometry (a spiral antenna?) you might consider two spirals that are rotated a bit with respect to each other and use the curves as boundaries for the spiral domain.

Regards
Edgar


Dear Edgar,

There's an option in CST for the width ,when you execute an equation based geometry.
So I was wondering if there's a similar option in COMSOL.

I'm attaching the geometry that I have created , its for a 2 arm spiral archimedian antenna.
You're suggesting on creating 4 different parametric curves?

Thanks a lot for your time and effort!!!!

Regards
Glenston
[QUOTE] Hi Glenston, I am not completely sure what you mean. A curve doesn't have a width. If you want to create a spiral geometry (a spiral antenna?) you might consider two spirals that are rotated a bit with respect to each other and use the curves as boundaries for the spiral domain. Regards Edgar [/QUOTE] Dear Edgar, There's an option in CST for the width ,when you execute an equation based geometry. So I was wondering if there's a similar option in COMSOL. I'm attaching the geometry that I have created , its for a 2 arm spiral archimedian antenna. You're suggesting on creating 4 different parametric curves? Thanks a lot for your time and effort!!!! Regards Glenston

Attachments:

Glenston Miranda
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Posted: 1 decade ago 24.08.2011, 10:00 GMT-4
Hi Edgar,

I understood how to create a spiral antenna.
Thanks a lot for your help.

Regards
Glenston
Hi Edgar, I understood how to create a spiral antenna. Thanks a lot for your help. Regards Glenston
Irfan
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Posted: 1 decade ago 06.09.2011, 14:43 GMT-4

Hi Edgar,

This model is very useful. And the polar plot is very fast.
Could you explain why you used the expressions in the angle data section. And should i use the same expressions for any model when ploting the far field pattern?

Cheers,
Khalid


Hi Khalid

How you opened the Edgar's Model I could not open it, I am using 4.2

Thanks

Irfan

[QUOTE] Hi Edgar, This model is very useful. And the polar plot is very fast. Could you explain why you used the expressions in the angle data section. And should i use the same expressions for any model when ploting the far field pattern? Cheers, Khalid [/QUOTE] Hi Khalid How you opened the Edgar's Model I could not open it, I am using 4.2 Thanks Irfan
Edgar Kaiser
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Posted: 1 decade ago 07.09.2011, 04:38 GMT-4
Irfan,

it is a version 4.1 model. I recently updated to 4.2 and can open it without problems in 4.2

Cheers
Edgar
Irfan, it is a version 4.1 model. I recently updated to 4.2 and can open it without problems in 4.2 Cheers Edgar

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