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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Radiate power of an isolated patch antenna

Posted 2012年10月1日 GMT-4 03:50 RF & Microwave Engineering, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.3 8 Replies

Matth Duperron
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Hi,

I'm trying to calculate the radiated and absorbed powers of an isolated patch antenna.
I create a box with 4 PML. When i change the horizontal dimension of my box, the calculated powers vary significantly, even if the box size is large compare to the antenna size. There is some horizontal interferences that we can see on the field map, or on the calculated power.
I tryied different configuration: size box, mesh, pml, source... but I still have this undesirable variation.
If anyone have an idea.
Thanks.

(the mph file with the results is too big, so I delete the solution to attach it to the discussion. The jpg file shows the absorbed power in the metal near the antenna vs the horizontal size of the box, we can clearly see the undesirable oscillation)
8 Replies Last Post 2012年10月2日 GMT-4 12:50
Edgar Kaiser
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Posted: 1 decade ago 2012年10月1日 GMT-4 05:37

Hi,

you could try to replace the box by a cylinder and make the PML at least a wavelength thick and change its geometry to cylindical.

Cheers
Edgar
Hi, you could try to replace the box by a cylinder and make the PML at least a wavelength thick and change its geometry to cylindical. Cheers Edgar
Matth Duperron
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Posted: 1 decade ago 2012年10月1日 GMT-4 10:39
There's the same problem with a cylindrical box.
There's the same problem with a cylindrical box.

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Erik Shipton
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Posted: 1 decade ago 2012年10月1日 GMT-4 13:05
edit: i just saw edgar's post. nevemind.

could it be your PML thickness isn't enough? it looks like your PML isn't even a wavelength thick hPML=2e-6 while your wavelength is ~3.3e-6 unless i did something wrong(your frequency is 90THz). i was under the impression the PML's should be at least a wavelength or more.
edit: i just saw edgar's post. nevemind. could it be your PML thickness isn't enough? it looks like your PML isn't even a wavelength thick hPML=2e-6 while your wavelength is ~3.3e-6 unless i did something wrong(your frequency is 90THz). i was under the impression the PML's should be at least a wavelength or more.
Alexander Kuznetsov
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Posted: 1 decade ago 2012年10月1日 GMT-4 14:39
your field is on the order of 10^(-15). Is it just computational error you are seeing?
your field is on the order of 10^(-15). Is it just computational error you are seeing?
Matth Duperron
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Posted: 1 decade ago 2012年10月2日 GMT-4 02:54
Thanks for all your responses.
Unfortunatelly, that didn't work: I try PML of 5µm, 10µm and 20µm, I multiply the incident field amplitude by 10^5 (power are now ~10-100W/m), but I still have the same oscillations.
If I suppress my antenna and keep just the mirror, the interference appear on the reflected field. If I suppress all (just plane wave in the air) the field is ok. That's really strange beacause the interference are horizontal (and the reflected field is in the vertical direction).
Do you know if it's a good choice to use background field to work with a mirror system?

(the optimal configuration seems to be a large rectangular box, see the attached picture)
Thanks for all your responses. Unfortunatelly, that didn't work: I try PML of 5µm, 10µm and 20µm, I multiply the incident field amplitude by 10^5 (power are now ~10-100W/m), but I still have the same oscillations. If I suppress my antenna and keep just the mirror, the interference appear on the reflected field. If I suppress all (just plane wave in the air) the field is ok. That's really strange beacause the interference are horizontal (and the reflected field is in the vertical direction). Do you know if it's a good choice to use background field to work with a mirror system? (the optimal configuration seems to be a large rectangular box, see the attached picture)

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Matth Duperron
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Posted: 1 decade ago 2012年10月2日 GMT-4 04:37

Attachments:

Matth Duperron
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Posted: 1 decade ago 2012年10月2日 GMT-4 09:30
I've found where the problem comes from: there's a surface plasmon on the interface metal-air of the mirror. And this propagating wave isn't absorb by the PML.
I'll search if anyone have already find a solution to this problem on the forum, but if you have any idea: this topic is still available.
I've found where the problem comes from: there's a surface plasmon on the interface metal-air of the mirror. And this propagating wave isn't absorb by the PML. I'll search if anyone have already find a solution to this problem on the forum, but if you have any idea: this topic is still available.
Alexander Kuznetsov
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Posted: 1 decade ago 2012年10月2日 GMT-4 12:50
have you tried changing PML's parameters? Make sure to change PML type to General to see the effect...
have you tried changing PML's parameters? Make sure to change PML type to General to see the effect...

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