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Calculating total power in the far field

Posted Apr 30, 2019, 2:54 p.m. EDT RF & Microwave Engineering, Wave Optics Version 5.4 5 Replies

Amer Abu Arisheh
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Hello

How can I find the total power in the far field? Can I do this by integrating the following expression over the simulation sphere:

ewfd.(normE^2)/(2*Z0_const)

When I do this I get a very small value

5 Replies Last Post May 2, 2019, 6:50 p.m. EDT
Pu
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Posted: 5 years ago Apr 30, 2019, 6:12 p.m. EDT

It depends on what your problem looks like.

-------------------
ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
It depends on what your problem looks like.
Amer Abu Arisheh
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Posted: 5 years ago Apr 30, 2019, 7:17 p.m. EDT

It depends on what your problem looks like.

Thanks for your reply. I illuminate a nanosphere with a plane wave and I want to find the total power scattered in the far field. When I integrate ewfd.(normE^2)/(2Z0const) over the main sphere I get an extremely small value.

>It depends on what your problem looks like. Thanks for your reply. I illuminate a nanosphere with a plane wave and I want to find the total power scattered in the far field. When I integrate ewfd.(normE^2)/(2Z0const) over the main sphere I get an extremely small value.
Pu
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Posted: 5 years ago May 1, 2019, 12:25 p.m. EDT

You can simply integrate the Poynting vector over a closed surface.

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ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
You can simply integrate the Poynting vector over a closed surface.
Amer Abu Arisheh
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Posted: 5 years ago May 1, 2019, 6:43 p.m. EDT

You can simply integrate the Poynting vector over a closed surface.

Thanks alot for your reply. I'm interested in the total power scattered to the far field. I made a typo error in the expression in my previous power.. I meant it is ewfd.(normEfar^2)/(2Z0const)

At what distance should I make the surface integration? The variable normEfar is calculated in comsol at 1[m] so I think it is constant with the distance..it only differs with the angle as shown in the attached figure.. so why my result differ when I integrate over closed surfaces with different radius?

>You can simply integrate the Poynting vector over a closed surface. Thanks alot for your reply. I'm interested in the total power scattered to the far field. I made a typo error in the expression in my previous power.. I meant it is ewfd.(normEfar^2)/(2Z0const) At what distance should I make the surface integration? The variable normEfar is calculated in comsol at 1[m] so I think it is constant with the distance..it only differs with the angle as shown in the attached figure.. so why my result differ when I integrate over closed surfaces with different radius?

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Pu
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Posted: 5 years ago May 2, 2019, 6:50 p.m. EDT

Energy conservation ensures one can calculate the power in the near field. Or maybe you are interested in more than the final result?

-------------------
ZHANG, Pu
School of Physics,
Huazhong University of Science and Technology
Energy conservation ensures one can calculate the power in the near field. Or maybe you are interested in more than the final result?

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