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How to export the data of far-field pattern

Posted 29.09.2015, 00:07 GMT-4 RF & Microwave Engineering, Acoustics & Vibrations, Results & Visualization Version 5.1 4 Replies

Yuliang Wang
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Hi! I am a newbie to COMSOL and I just managed to compute the scattering of electromagnetic wave by a PEC ellipsoid. I exported the data of far-field pattern to a csv file. As far as I know, the far-field pattern are the amplitude of the electric field defined on the unit sphere (as a function of the zenith and azimuth angle). However, the (x,y,z) coordinates in the data file are apparently not on the unit sphere.

How to export the far-field pattern as a function of the two angles?
4 Replies Last Post 20.11.2015, 01:06 GMT-5
Gunnar Andersson COMSOL Employee

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Posted: 9 years ago 29.09.2015, 02:16 GMT-4
However, the (x,y,z) coordinates in the data file are apparently not on the unit sphere.


If you export plot data from a 3D far field plot, then you get the following columns in the data file:

x y z Color

The direction of the (x, y, z) vector corresponds to a point on the unit sphere. The magnitude of the vector is the value of the expression entered in the Expression section when evaluated on that point.

The Color is the value of the expression in the Color section for the same point on the unit sphere.
[QUOTE] However, the (x,y,z) coordinates in the data file are apparently not on the unit sphere.[/QUOTE] If you export plot data from a 3D far field plot, then you get the following columns in the data file: x y z Color The direction of the (x, y, z) vector corresponds to a point on the unit sphere. The magnitude of the vector is the value of the expression entered in the Expression section when evaluated on that point. The Color is the value of the expression in the Color section for the same point on the unit sphere.
Yuliang Wang
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Posted: 9 years ago 29.09.2015, 03:32 GMT-4
Thank you very much. I understand your explanations. In fact, I found a better way to export the far-field pattern for my purpose is to use a 2D far-field plot. But there is another question. In the color section, I selected ewfd.Efarx, which is assumed to be the x component of the electric far-field pattern. However, the output data is only a real value. How to output the complete complex valued far-field pattern? I do understand the physical electric field is a real number. Maybe I missed something here? I am from a mathematical background.
Thank you very much. I understand your explanations. In fact, I found a better way to export the far-field pattern for my purpose is to use a 2D far-field plot. But there is another question. In the color section, I selected ewfd.Efarx, which is assumed to be the x component of the electric far-field pattern. However, the output data is only a real value. How to output the complete complex valued far-field pattern? I do understand the physical electric field is a real number. Maybe I missed something here? I am from a mathematical background.
Gunnar Andersson COMSOL Employee

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Posted: 9 years ago 29.09.2015, 03:40 GMT-4

Thank you very much. I understand your explanations. In fact, I found a better way to export the far-field pattern for my purpose is to use a 2D far-field plot. But there is another question. In the color section, I selected ewfd.Efarx, which is assumed to be the x component of the electric far-field pattern. However, the output data is only a real value. How to output the complete complex valued far-field pattern? I do understand the physical electric field is a real number. Maybe I missed something here? I am from a mathematical background.


You can unfortunately only export the real part of the color expression as this is what the plot evaluates - the imaginary part of the color would be ignored anyway.

To export both the real and imaginary parts of the color expression, you can use the following workaround: Create two plots, one with real(ewfd.Efarx) as color expression and one with imag(ewfd.Efarx) as color expression. Then export the data using two plot data export features. This gives you two files. It's not an ideal solution, but it gives you the data.

[QUOTE] Thank you very much. I understand your explanations. In fact, I found a better way to export the far-field pattern for my purpose is to use a 2D far-field plot. But there is another question. In the color section, I selected ewfd.Efarx, which is assumed to be the x component of the electric far-field pattern. However, the output data is only a real value. How to output the complete complex valued far-field pattern? I do understand the physical electric field is a real number. Maybe I missed something here? I am from a mathematical background. [/QUOTE] You can unfortunately only export the real part of the color expression as this is what the plot evaluates - the imaginary part of the color would be ignored anyway. To export both the real and imaginary parts of the color expression, you can use the following workaround: Create two plots, one with real(ewfd.Efarx) as color expression and one with imag(ewfd.Efarx) as color expression. Then export the data using two plot data export features. This gives you two files. It's not an ideal solution, but it gives you the data.
Yuliang Wang
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Posted: 9 years ago 20.11.2015, 01:06 GMT-5
Thank you Gunnar!

Now I would like to export the far-field pattern for a fixed obstacle but with a sweep of incident angles. I solved the problem by using a parameter sweep but I don't know how to export the far-field pattern for all incident angles to a single file or individual files with parameter dependent file names. I watched a video about exporting parameter sweep results using tables, but it does not work for far-field pattern.
Thank you Gunnar! Now I would like to export the far-field pattern for a fixed obstacle but with a sweep of incident angles. I solved the problem by using a parameter sweep but I don't know how to export the far-field pattern for all incident angles to a single file or individual files with parameter dependent file names. I watched a video about exporting parameter sweep results using tables, but it does not work for far-field pattern.

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