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Imitate the radiation pattern of an antenna

Posted Mar 26, 2015, 10:47 a.m. EDT RF & Microwave Engineering 4 Replies

Xavier Faget
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Hi,

I am quite new on Comsol and i am trying to imitate the field emitted by the radiation pattern of an antenna.

In other words, I have a radiation pattern antenna, and I would like to have the same field on COMSOL without importing the geometry of my antenna.

I have read all the models of the library but i have not yet find the good way to do it.
Someone has any tips for me?

Cordially,
Xavier
4 Replies Last Post Mar 27, 2015, 5:47 a.m. EDT
Edgar J. Kaiser Certified Consultant
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Posted: 10 years ago Mar 26, 2015, 12:29 p.m. EDT
Xavier,

your radiation pattern is probably a far field pattern. COMSOL calculates the near field and finds the far field by the Stratton-Chu method applied to the outer boundary of the near field.

So you would have to invert the Stratton-Chu method to find a solution on the near field boundary. I doubt that there is an unambiguous solution to that.

The other question is, what do you want to do with the near field corresponding to the far field pattern? There might be other option to achieve your goal.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Xavier, your radiation pattern is probably a far field pattern. COMSOL calculates the near field and finds the far field by the Stratton-Chu method applied to the outer boundary of the near field. So you would have to invert the Stratton-Chu method to find a solution on the near field boundary. I doubt that there is an unambiguous solution to that. The other question is, what do you want to do with the near field corresponding to the far field pattern? There might be other option to achieve your goal. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com
Xavier Faget
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Posted: 10 years ago Mar 26, 2015, 1:37 p.m. EDT
Yep, have the desired far-field by reverse Stratton-Chu seems to be hard !

When I create a port with the RF module, I would like produce the same far-field than a real antenna does. no matter the near field.

Perhaps there is a way to do it analytically. With a port define by the user , input parameters are f[Hz],P[W],E(Ex,Ey,Ez)[V\m] and beta[m\rad].
Perhaps I can create the far-field desired by adjusting this parameters?

Another solution could be with an array of dipoles, but it seems quite complicated.

Cordially,

Xavier
Yep, have the desired far-field by reverse Stratton-Chu seems to be hard ! When I create a port with the RF module, I would like produce the same far-field than a real antenna does. no matter the near field. Perhaps there is a way to do it analytically. With a port define by the user , input parameters are f[Hz],P[W],E(Ex,Ey,Ez)[V\m] and beta[m\rad]. Perhaps I can create the far-field desired by adjusting this parameters? Another solution could be with an array of dipoles, but it seems quite complicated. Cordially, Xavier
Robert Koslover Certified Consultant
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Posted: 10 years ago Mar 26, 2015, 10:10 p.m. EDT
Aside from certain pathologically-shaped geometries (such as a shell-volume actually surrounding the antenna in question, but not containing it), any reasonable finite-extent volume that lies entirely within the "far-field" region of an antenna would indeed be entirely equivalent to that same volume being subjected to plane-wave illumination. Is that what you are trying to do? Are you simply trying to impose or launch a plane wave in/across your test volume? If so, you can do that in a number of ways. But the easiest is to use the "scattered-field" formulation. If you don't already know how to use that, look it up in the help system and try it out. I think there are some examples of using it in the model library. You may be pleasantly surprised with how easy it is to use.
Aside from certain pathologically-shaped geometries (such as a shell-volume actually surrounding the antenna in question, but not containing it), any reasonable finite-extent volume that lies entirely within the "far-field" region of an antenna would indeed be entirely equivalent to that same volume being subjected to plane-wave illumination. Is that what you are trying to do? Are you simply trying to impose or launch a plane wave in/across your test volume? If so, you can do that in a number of ways. But the easiest is to use the "scattered-field" formulation. If you don't already know how to use that, look it up in the help system and try it out. I think there are some examples of using it in the model library. You may be pleasantly surprised with how easy it is to use.
Xavier Faget
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Posted: 10 years ago Mar 27, 2015, 5:47 a.m. EDT
For be more precise. I emit an EM wave from a port, the wave illuminate an object and after that, I receive the field with an other port in order to compute S_parameter. All of this in 2D. It work great !

But now I would like to adjust my lighting as much as possible to a real antenna. For exemple see the parameters and radiations pattern of www.ets-lindgren.com/charts/3106B

Is it possible to do this? I would like if possible to conserve the calculation of S-parameters.

It would be also great to obtain the same VSWR :)

Kind regards,
Xavier

For be more precise. I emit an EM wave from a port, the wave illuminate an object and after that, I receive the field with an other port in order to compute S_parameter. All of this in 2D. It work great ! But now I would like to adjust my lighting as much as possible to a real antenna. For exemple see the parameters and radiations pattern of http://www.ets-lindgren.com/charts/3106B Is it possible to do this? I would like if possible to conserve the calculation of S-parameters. It would be also great to obtain the same VSWR :) Kind regards, Xavier

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