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How to add AC source

Posted 17.05.2011, 21:20 GMT-4 Low-Frequency Electromagnetics, MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Structural Mechanics Version 3.5a 18 Replies

Tianying Chang
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Hi,
In the simulation, a spiral antenna is excited by AC source in RF module. Physics is emw and study type is frequency domain. I want to use a square-wave AC to excite two terminals of antenna. My question is how to add the AC source. Is the lumped port used? If so, how to show square-wave voltage in lumped port? Thanks a lot in advance.
18 Replies Last Post 18.01.2013, 04:51 GMT-5
Tianying Chang
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Posted: 1 decade ago 18.05.2011, 11:27 GMT-4
Could anyone help to answer this question? Thanks.
Could anyone help to answer this question? Thanks.
Edgar Kaiser
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Posted: 1 decade ago 18.05.2011, 11:57 GMT-4
Hi,

I think a frequency domain analysis is always based on harmonic excitation and you can't apply a square wave. The frequency response analysis can show you what way your antenna responds to the spectral components of the square wave. You probably could run a parametric study using a sufficient number of harmonics of your square wave and add up the results with appropriate scaling factors. However, I don't know how to add results from a parametric study.

If you want to apply a real square wave you will need to perform a transient analysis and define the port input as a function of time.

Cheers
Edgar
Hi, I think a frequency domain analysis is always based on harmonic excitation and you can't apply a square wave. The frequency response analysis can show you what way your antenna responds to the spectral components of the square wave. You probably could run a parametric study using a sufficient number of harmonics of your square wave and add up the results with appropriate scaling factors. However, I don't know how to add results from a parametric study. If you want to apply a real square wave you will need to perform a transient analysis and define the port input as a function of time. Cheers Edgar
Tianying Chang
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Posted: 1 decade ago 18.05.2011, 12:08 GMT-4
Hi Edgar,

Thanks a lot for your reply. Your point makes sense. However, if I do not add a square-wave AC source, do you know how to add a sinusoidal AC source? My issue is I do not know how to use a kind of AC source in lumped port.

Best,
Tianying
Hi Edgar, Thanks a lot for your reply. Your point makes sense. However, if I do not add a square-wave AC source, do you know how to add a sinusoidal AC source? My issue is I do not know how to use a kind of AC source in lumped port. Best, Tianying
Edgar Kaiser
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Posted: 1 decade ago 19.05.2011, 04:04 GMT-4
Hi Tianying,

it is easy. Switch on wave excitation in the lumped port node, specify the terminal type and respective input and choose your frequencies in the Frequency domain study node.

Cheers
Edgar
Hi Tianying, it is easy. Switch on wave excitation in the lumped port node, specify the terminal type and respective input and choose your frequencies in the Frequency domain study node. Cheers Edgar
Tianying Chang
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Posted: 1 decade ago 19.05.2011, 19:39 GMT-4
Hi Edgar,

Thanks a lot. I will try it.

Best,
Tianying
Hi Edgar, Thanks a lot. I will try it. Best, Tianying
Edgar Kaiser
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Posted: 1 decade ago 20.05.2011, 03:20 GMT-4
Hi Tianying,

I recently had some problems with the lumped port. Actually the coaxial and uniform type didn't work and the solver terminated with an error message that is not very instructive, as most error messages from COMSOL :-(.

Finally I could set up a user defined lumped port that requires defining width, height and direction of the excitation gap.

A support case with COMSOL support is running. If you make it to define a uniform or coaxial port I would be interested to see how you did it.

Cheers
Edgar

Hi Tianying, I recently had some problems with the lumped port. Actually the coaxial and uniform type didn't work and the solver terminated with an error message that is not very instructive, as most error messages from COMSOL :-(. Finally I could set up a user defined lumped port that requires defining width, height and direction of the excitation gap. A support case with COMSOL support is running. If you make it to define a uniform or coaxial port I would be interested to see how you did it. Cheers Edgar
Tianying Chang
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Posted: 1 decade ago 23.05.2011, 16:31 GMT-4
Hi Edgar,

An error massage often occurs when I use the lumped port. More, I have not used the user defined lumped port. I am sorry for not helping you. I am trying my best to solve this issue. I will tell you once I make it.

Best regards,
Tianying
Hi Edgar, An error massage often occurs when I use the lumped port. More, I have not used the user defined lumped port. I am sorry for not helping you. I am trying my best to solve this issue. I will tell you once I make it. Best regards, Tianying
Glenston Miranda
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Posted: 1 decade ago 29.08.2011, 06:55 GMT-4

Hi Tianying,

I recently had some problems with the lumped port. Actually the coaxial and uniform type didn't work and the solver terminated with an error message that is not very instructive, as most error messages from COMSOL :-(.

Finally I could set up a user defined lumped port that requires defining width, height and direction of the excitation gap.

A support case with COMSOL support is running. If you make it to define a uniform or coaxial port I would be interested to see how you did it.

Cheers
Edgar


Hi Edgar,

I'm trying to excite the spiral antenna using a 1mm rod in the center .
It worked in CST. I'm trying to simulate it using a single terminal .
Is it possible to excite it using lumped port ?
I tried with the user defined lumped port , it did not give me an error but the results are wrong.
Lumped port in all other forms gave me an error. I also used the port boundary condition I got an error again

Theoretically you need 2 terminals for port . But since the excitation rod is off very small
magnitude it sees the ground of the coaxial cable it self.

It would be great if you could help me in this.
Thanks a lot for being active on this discussion forum, your comments have proved very instrumental.

Regards
Glenston

[QUOTE] Hi Tianying, I recently had some problems with the lumped port. Actually the coaxial and uniform type didn't work and the solver terminated with an error message that is not very instructive, as most error messages from COMSOL :-(. Finally I could set up a user defined lumped port that requires defining width, height and direction of the excitation gap. A support case with COMSOL support is running. If you make it to define a uniform or coaxial port I would be interested to see how you did it. Cheers Edgar [/QUOTE] Hi Edgar, I'm trying to excite the spiral antenna using a 1mm rod in the center . It worked in CST. I'm trying to simulate it using a single terminal . Is it possible to excite it using lumped port ? I tried with the user defined lumped port , it did not give me an error but the results are wrong. Lumped port in all other forms gave me an error. I also used the port boundary condition I got an error again Theoretically you need 2 terminals for port . But since the excitation rod is off very small magnitude it sees the ground of the coaxial cable it self. It would be great if you could help me in this. Thanks a lot for being active on this discussion forum, your comments have proved very instrumental. Regards Glenston
Edgar Kaiser
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Posted: 1 decade ago 29.08.2011, 07:30 GMT-4
Glenston,

I have some difficulties to get the picture. If you could provide your model, it might be easier to have a look.

Cheers
Edgar
Glenston, I have some difficulties to get the picture. If you could provide your model, it might be easier to have a look. Cheers Edgar
Glenston Miranda
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Posted: 1 decade ago 29.08.2011, 08:14 GMT-4

Glenston,

I have some difficulties to get the picture. If you could provide your model, it might be easier to have a look.

Cheers
Edgar



I'm communicating with you through 2 threads.
Sorry for that.

Anyways i'm attaching the model again .
Thanks a lot for your help.

Regards
Glenston
[QUOTE] Glenston, I have some difficulties to get the picture. If you could provide your model, it might be easier to have a look. Cheers Edgar [/QUOTE] I'm communicating with you through 2 threads. Sorry for that. Anyways i'm attaching the model again . Thanks a lot for your help. Regards Glenston

Attachments:

Glenston Miranda
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Posted: 1 decade ago 29.08.2011, 08:40 GMT-4
This attachment is with perfect electric boundary conditions

Regards
Glenston
This attachment is with perfect electric boundary conditions Regards Glenston

Attachments:

Vikram Kumar Singh
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Posted: 1 decade ago 15.09.2011, 05:36 GMT-4
Hello sir

I also need to apply AC source to my model.

i given as

Function name : AC

Type : sine
Angular frequency : 2*pi*1e8
Phase : 0
Amplitude:2

and then through electric potential i called function name as

V0 : AC

but it is saying unknown variable AC .
please help i need to apply AC signal ,how can i apply?


Hello sir I also need to apply AC source to my model. i given as Function name : AC Type : sine Angular frequency : 2*pi*1e8 Phase : 0 Amplitude:2 and then through electric potential i called function name as V0 : AC but it is saying unknown variable AC . please help i need to apply AC signal ,how can i apply?
Andy Liu
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Posted: 1 decade ago 09.02.2012, 02:00 GMT-5
I have the same problem....

I use AC/DC module, quasi-static electric current.

I set the boundary Vo=5, or Vo=5*sin(2*pi*nu_emqvw*t)

But when I solve it, both show "No subdomain scalar data on screen." for the electric potential value

Anyone know how to do a AC simulations?


============================================
I searched some previous threads and found something useful...

www.comsol.com/community/forums/general/thread/23481/

This might help. I will try it now
I have the same problem.... I use AC/DC module, quasi-static electric current. I set the boundary Vo=5, or Vo=5*sin(2*pi*nu_emqvw*t) But when I solve it, both show "No subdomain scalar data on screen." for the electric potential value Anyone know how to do a AC simulations? ============================================ I searched some previous threads and found something useful... http://www.comsol.com/community/forums/general/thread/23481/ This might help. I will try it now
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 09.02.2012, 03:58 GMT-5
Hi

it depends what you want: transient or steady state AC fixed frequency or frequency domain scan ?

You must change the solver accordingly and either use amplitude phase, or with the sin(2*pi*f*t) explicitely.

Note "t" is only defined once you launch a time / transient solver

ANd do notforget that EC is "quasi standard hecen loe frequency) again check the doc ACDC versus RF

--
Good luck
Ivar
Hi it depends what you want: transient or steady state AC fixed frequency or frequency domain scan ? You must change the solver accordingly and either use amplitude phase, or with the sin(2*pi*f*t) explicitely. Note "t" is only defined once you launch a time / transient solver ANd do notforget that EC is "quasi standard hecen loe frequency) again check the doc ACDC versus RF -- Good luck Ivar
Megha Agrawal
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Posted: 1 decade ago 16.07.2012, 06:40 GMT-4

Hi

it depends what you want: transient or steady state AC fixed frequency or frequency domain scan ?

You must change the solver accordingly and either use amplitude phase, or with the sin(2*pi*f*t) explicitely.

Note "t" is only defined once you launch a time / transient solver

ANd do notforget that EC is "quasi standard hecen loe frequency) again check the doc ACDC versus RF

--
Good luck
Ivar


Hi Ivar
Thanks for the reply. I wanted to use AC voltage as an input into piezoelectric devices physics. According to your post above I should use TIme Dependent study and then put sin(2*pi*f*t) as input to piezo - Electrical Potential...right? but it does not take the input. sin(2*pi*f*t) is red indicating it cannot take the input. am i making a mistake? should pi be defined?

Thanks in advance
Megha
[QUOTE] Hi it depends what you want: transient or steady state AC fixed frequency or frequency domain scan ? You must change the solver accordingly and either use amplitude phase, or with the sin(2*pi*f*t) explicitely. Note "t" is only defined once you launch a time / transient solver ANd do notforget that EC is "quasi standard hecen loe frequency) again check the doc ACDC versus RF -- Good luck Ivar [/QUOTE] Hi Ivar Thanks for the reply. I wanted to use AC voltage as an input into piezoelectric devices physics. According to your post above I should use TIme Dependent study and then put sin(2*pi*f*t) as input to piezo - Electrical Potential...right? but it does not take the input. sin(2*pi*f*t) is red indicating it cannot take the input. am i making a mistake? should pi be defined? Thanks in advance Megha
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 16.07.2012, 14:25 GMT-4
Hi

normally it should work, but could it be that "f" is already used, or that it does not have the units of "Hz" ?

If you have a steady state sinus excitation I would recommend that you consider the frequency domain sweep using a harmonic development of the PDE equations, check the doc

--
Good luck
Ivar
Hi normally it should work, but could it be that "f" is already used, or that it does not have the units of "Hz" ? If you have a steady state sinus excitation I would recommend that you consider the frequency domain sweep using a harmonic development of the PDE equations, check the doc -- Good luck Ivar
Jiujiang Wang
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Posted: 1 decade ago 18.01.2013, 03:41 GMT-5
Hello!

Do you know how to add AC source now?

Will you please describe how to do it in COMSOL 4.2?

Thanks!
Hello! Do you know how to add AC source now? Will you please describe how to do it in COMSOL 4.2? Thanks!
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18.01.2013, 04:51 GMT-5
Hi

check the doc for Frequency solver or harmonic development (you define amplitudes and the frequency, and your physics is described in omega (frequency domain) (unfortunately I have only latest 4.3a up running ;)

--
Good luck
Ivar
Hi check the doc for Frequency solver or harmonic development (you define amplitudes and the frequency, and your physics is described in omega (frequency domain) (unfortunately I have only latest 4.3a up running ;) -- Good luck Ivar

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