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Frequency Domain to Time Domain , COMSOL 5.2

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Hi,

I have a design which involves two antenna and a gap in between. I have estimated the e-field intensity through the gap, where e-field is a function of frequency and space. However, I need to transfer the plots and the data of e-field in frequency domain to the time domain.

I would like to know how can I transfer the data and plots of e-field to time domain. I am using the RF module, COMSOL 5.2.

Please kindly let me know. Thanks.

7 Replies Last Post 27.07.2016, 11:42 GMT-4

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Posted: 8 years ago 25.07.2016, 14:00 GMT-4
Your question is somewhat unclear -- repeating an unclear question doesn't help. You can just post it once.

Anyway, what do you mean by "transfer". Certainly you can run both a time and frequency domain study on the same geometry and have both data sets available at the same time. Is that what you want to do? If that's not it, please make your question clearer.
Your question is somewhat unclear -- repeating an unclear question doesn't help. You can just post it once. Anyway, what do you mean by "transfer". Certainly you can run both a time and frequency domain study on the same geometry and have both data sets available at the same time. Is that what you want to do? If that's not it, please make your question clearer.

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Posted: 8 years ago 25.07.2016, 14:18 GMT-4
Hi Chris,

Sorry for posting it again. But I need help that's why. To make it more clear.

I have e-field distribution (attached fig.1) for a defined antenna structure at a certain frequency. I would like to plot the time-dependent e-field distribution (E-field Vs Time) along a certain line of the structure. In this case, I am expecting the time-dependent e-field distribution to be non-sinusoidal in nature.

Can you please suggest me how can I plot E field Vs time along a specific line in the antenna structure from the E-field distribution that I have obtained from frequency domain in frequency (attached fig.1).

Please let me know if anything is still unclear. Thanks Chris !
Hi Chris, Sorry for posting it again. But I need help that's why. To make it more clear. I have e-field distribution (attached fig.1) for a defined antenna structure at a certain frequency. I would like to plot the time-dependent e-field distribution (E-field Vs Time) along a certain line of the structure. In this case, I am expecting the time-dependent e-field distribution to be non-sinusoidal in nature. Can you please suggest me how can I plot E field Vs time along a specific line in the antenna structure from the E-field distribution that I have obtained from frequency domain in frequency (attached fig.1). Please let me know if anything is still unclear. Thanks Chris !


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Posted: 8 years ago 26.07.2016, 12:54 GMT-4
Anyone can help with this problem ? Please let me know. Thanks again.
Anyone can help with this problem ? Please let me know. Thanks again.

Edgar J. Kaiser Certified Consultant

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Posted: 8 years ago 26.07.2016, 13:47 GMT-4
Your picture doesn't explain much.
First of all, there is no time in a frequency domain study. If you have a frequency sweep you can do an FFT to transform it to time domain.
It is completely unclear how a line plot would correspond to a time domain plot. The line plot gives a spatial distribution of the E-field.
You can display a phase plot for any point or global quantity of the model. But this will always be a harmonic curve of the study frequency.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Your picture doesn't explain much. First of all, there is no time in a frequency domain study. If you have a frequency sweep you can do an FFT to transform it to time domain. It is completely unclear how a line plot would correspond to a time domain plot. The line plot gives a spatial distribution of the E-field. You can display a phase plot for any point or global quantity of the model. But this will always be a harmonic curve of the study frequency. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com

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Posted: 8 years ago 26.07.2016, 14:32 GMT-4
Hi Edgar,

The figure that I have attached here shows the e-field distribution at a particular frequency (10 THz in this case). However, a parametric sweep can be performed for higher frequencies as well. I was wondering if I can perform 'Frequency to Time FFT' study to obtain the time-dependent e-field distribution.


The thing that I actually want to do is - to obtain the voltage that is generated between the two antennas. The information that I got till now is the e-field distribution in frequency domain. In order to obtain the generated voltage, I want to integrate the time-dependent e-field distribution (non-sinusoidal in nature) along a path (dl), basically integral of E.dl which will give me Voltage generated along that path of the structure. I hope, I made it clear to you.

Would you please let me know, how I can perform 'Frequency to Time FFT' study after frequency sweep ? Please kindly let me know. Thanks a lot !
Hi Edgar, The figure that I have attached here shows the e-field distribution at a particular frequency (10 THz in this case). However, a parametric sweep can be performed for higher frequencies as well. I was wondering if I can perform 'Frequency to Time FFT' study to obtain the time-dependent e-field distribution. The thing that I actually want to do is - to obtain the voltage that is generated between the two antennas. The information that I got till now is the e-field distribution in frequency domain. In order to obtain the generated voltage, I want to integrate the time-dependent e-field distribution (non-sinusoidal in nature) along a path (dl), basically integral of E.dl which will give me Voltage generated along that path of the structure. I hope, I made it clear to you. Would you please let me know, how I can perform 'Frequency to Time FFT' study after frequency sweep ? Please kindly let me know. Thanks a lot !

Edgar J. Kaiser Certified Consultant

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Posted: 8 years ago 26.07.2016, 16:25 GMT-4
Hi Rishad,

the FFT procedures are explained in the COMSOL documentation and I would suggest to explore the application library.
For a line integral of the E-field you probably don't need to transform to time domain.

Cheers
Edgar

--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Hi Rishad, the FFT procedures are explained in the COMSOL documentation and I would suggest to explore the application library. For a line integral of the E-field you probably don't need to transform to time domain. Cheers Edgar -- Edgar J. Kaiser emPhys Physical Technology http://www.emphys.com

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Posted: 8 years ago 27.07.2016, 11:42 GMT-4
Thanks a lot. I will try to do as you said. Lets see how it goes ?
Thanks a lot. I will try to do as you said. Lets see how it goes ?

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