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A SMALL DOUBT ON PORT POWER VALUE !

Posted 19 nov. 2013, 01:41 UTC−5 RF & Microwave Engineering, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.2a, Version 4.3b 5 Replies

Binoy Chacko
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Hi all,

I am new to this software and I am trying to simulate a multi-layer structure on which plane electromagnetic wave is allowed to fall at normal incidence. I kept the port power at the default value(1 W) and after running the program I tried to check the power at the port 1. For that I use line integration to calculate sqrt(emw.Poavy^2 +emw.Poavx^2), but to my surprise the values I am getting is smaller than 1.

Can any one help me.
Thanks in advance...
5 Replies Last Post 29 nov. 2013, 01:32 UTC−5
Robert Koslover Certified Consultant
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Posted: 1 decade ago 20 nov. 2013, 13:31 UTC−5
Believe it or not, this is a feature, not a bug! When you specify the power going into the port, you are NOT actually forcing the boundary condition there into a state where it will actually have that net-overall power going into the port. Rather, you are only setting the forward-going power at that port. In general, there will also be a reverse-going power there, due to reflections or impedance mismatches somewhere in your system. This fact allows the proper computation of parameters such as S_11 (where the port is port #1), for example. When you do your integral of the power density over the port, both forward-directed and reverse-directed power flow is included, which is why you got less than 1W. (Note also that to get accurate numbers, you should generally mesh your ports relatively finely.)
Believe it or not, this is a feature, not a bug! When you specify the power going into the port, you are NOT actually forcing the boundary condition there into a state where it will actually have that net-overall power going into the port. Rather, you are only setting the forward-going power at that port. In general, there will also be a reverse-going power there, due to reflections or impedance mismatches somewhere in your system. This fact allows the proper computation of parameters such as S_11 (where the port is port #1), for example. When you do your integral of the power density over the port, both forward-directed and reverse-directed power flow is included, which is why you got less than 1W. (Note also that to get accurate numbers, you should generally mesh your ports relatively finely.)
Binoy Chacko
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Posted: 1 decade ago 21 nov. 2013, 01:43 UTC−5
Sir,

Thank For your reply..
I think I understand your explanation and In this case how will one able to find only the forward-going power at that port after running the program.

Regards
Binoy Chacko
Sir, Thank For your reply.. I think I understand your explanation and In this case how will one able to find only the forward-going power at that port after running the program. Regards Binoy Chacko
Robert Koslover Certified Consultant
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Posted: 1 decade ago 22 nov. 2013, 20:21 UTC−5
The "forward-going" power is 1W, since that is what you specified. P_total_input = P_forward - P_reverse. You can also do integrals over various surfaces (and/or volumes, if heating/loss is involved) to confirm energy conservation, and/or just to get a feel for the magnitude of numerical errors in the model. And you can plot quantities like S11, that relate to the power reflected. Look up "s-parameters" in the help system.
The "forward-going" power is 1W, since that is what you specified. P_total_input = P_forward - P_reverse. You can also do integrals over various surfaces (and/or volumes, if heating/loss is involved) to confirm energy conservation, and/or just to get a feel for the magnitude of numerical errors in the model. And you can plot quantities like S11, that relate to the power reflected. Look up "s-parameters" in the help system.
Maha Hashemi
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Posted: 1 decade ago 24 nov. 2013, 21:20 UTC−5

Sir,

Thank For your reply..
I think I understand your explanation and In this case how will one able to find only the forward-going power at that port after running the program.

Regards
Binoy Chacko


Dear Binoy,
A "PML" layer at the end of structure will help you to avoid any reverse wave!
Good luck! :)
[QUOTE] Sir, Thank For your reply.. I think I understand your explanation and In this case how will one able to find only the forward-going power at that port after running the program. Regards Binoy Chacko [/QUOTE] Dear Binoy, A "PML" layer at the end of structure will help you to avoid any reverse wave! Good luck! :)
Binoy Chacko
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Posted: 1 decade ago 29 nov. 2013, 01:32 UTC−5
hi,

Thank you for your reply.
We are trying to do as you said..

Regards
Binoy Chacko
hi, Thank you for your reply. We are trying to do as you said.. Regards Binoy Chacko

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