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Custom transient RF signal from specific location as seen by antenna

Posted 29.03.2012, 12:58 GMT-4 RF & Microwave Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.2a 5 Replies

Carl Pfendner
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Hello,

I'm relatively new to Comsol and I'm trying to model a situation for astrophysics research.

We are designing an antenna that lies inside a balloon that will be floating about the surface of the Earth at some distance. We want to observe a transient RF signal produced by a particle interaction in the atmosphere at a particular location. The interior surface of the balloon has a reflective surface that focuses the RF signal onto the antenna at the center of the balloon. We want to determine the response of the antenna to the signal produced at particular locations relative to the location of the balloon.

How can I make a custom transient "point source" RF signal that begins at one particular location (with no physically source present in the model, just the brief RF pulse) and propagates so that we can determine the response of the antenna? Since this signal is not actually spherically symmetric but is emitted within a cone, I would also like to know if it is possible to generate this pulse so that it propagates in a conical shape.

Thank you in advance,
Carl
5 Replies Last Post 02.05.2012, 05:27 GMT-4
Alexander Kuznetsov
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Posted: 1 decade ago 29.03.2012, 13:55 GMT-4
I think the easiest way to define conical source is to create an additional small antenna with conical pattern. I'm not sure if it's possible at all to create conical source without having it physically present in the model. And it's rather hard to correctly implement a source with a given pattern through boundary condition.
I think the easiest way to define conical source is to create an additional small antenna with conical pattern. I'm not sure if it's possible at all to create conical source without having it physically present in the model. And it's rather hard to correctly implement a source with a given pattern through boundary condition.
Edgar Kaiser
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Posted: 1 decade ago 30.03.2012, 05:20 GMT-4
isn't the source far enough away to treat the incoming signal as a plane wave? This would allow to use an RF port but you would need to use the RF module. AC/DC works only for model geometries that are much smaller than the AC wavelength.

Cheers
Edgar
isn't the source far enough away to treat the incoming signal as a plane wave? This would allow to use an RF port but you would need to use the RF module. AC/DC works only for model geometries that are much smaller than the AC wavelength. Cheers Edgar
Carl Pfendner
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Posted: 1 decade ago 30.03.2012, 15:55 GMT-4
I think you're right about the approximation of the plane wave. I had realized that shortly after posting the message. So I will just use a plane wave. But still, out of curiosity, it would be interesting to try to make a conical wavefront rather than a spherical or plane wave.

Primarily I was referring more to the practical matters of getting the pulse set up in the first place but I think I've figured most of the steps needed to do that. I will keep this thread updated if there's anything else that seems to be an issue.

Thanks for the advice,
Carl
I think you're right about the approximation of the plane wave. I had realized that shortly after posting the message. So I will just use a plane wave. But still, out of curiosity, it would be interesting to try to make a conical wavefront rather than a spherical or plane wave. Primarily I was referring more to the practical matters of getting the pulse set up in the first place but I think I've figured most of the steps needed to do that. I will keep this thread updated if there's anything else that seems to be an issue. Thanks for the advice, Carl
Carl Pfendner
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Posted: 1 decade ago 06.04.2012, 16:38 GMT-4
I thought I had the details of the plane-wave figured out but I do not. I've tried to recreate the results of the Gaussian laser pulse example model from the Comsol example archive but I cannot get the wave to propagate through the medium in that model. How can I get a transient e-m wave to propagate through a medium?

Carl
I thought I had the details of the plane-wave figured out but I do not. I've tried to recreate the results of the Gaussian laser pulse example model from the Comsol example archive but I cannot get the wave to propagate through the medium in that model. How can I get a transient e-m wave to propagate through a medium? Carl
Muhammad Mohsin Rehman
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Posted: 1 decade ago 02.05.2012, 05:27 GMT-4
Hi Carl,

Did you solve your problem?
I am also trying to model a transient electromagnetic source for heating the fluid, can you please help me?

Many thanks in advance.
Hi Carl, Did you solve your problem? I am also trying to model a transient electromagnetic source for heating the fluid, can you please help me? Many thanks in advance.

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