Far field calculation in metasurface

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Hi guys. Now I am facing a problem of getting far field from an array. When calculating the near field, periodic condition is applied and only a single unit is calculated. But when I tried to apply far field node in the model, I think COMSOL only do stratton-chu equation on the single unit but not the whole array. Since I want to calculate the far field from the whole array, I think I need the integral on the whole surface of the whole array. Is there a solution for this problem now? Thanks!


10 Replies Last Post 18 set 2025, 00:04 GMT-4
Robert Koslover Certified Consultant

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Posted: 2 days ago 16 set 2025, 20:27 GMT-4
Updated: 2 days ago 16 set 2025, 20:36 GMT-4

I recommend you study the example model: "microstrip_patch_antenna_periodic" in the Comsol-supplied Application Library. "Modeling of a Phased Array Antenna" Application ID: 88011 . See https://www.comsol.com/model/modeling-of-a-phased-array-antenna-88011 . Be sure to read the discussion of how the far field computations are done in the associated .pdf file. You need to apply an array factor.

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Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
I recommend you study the example model: "microstrip_patch_antenna_periodic" in the Comsol-supplied Application Library. "Modeling of a Phased Array Antenna" Application ID: 88011 . See https://www.comsol.com/model/modeling-of-a-phased-array-antenna-88011 . Be sure to read the discussion of how the far field computations are done in the associated .pdf file. You need to apply an array factor.

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Posted: 2 days ago 16 set 2025, 20:52 GMT-4
Updated: 1 day ago 17 set 2025, 08:43 GMT-4

Yes! From the math structure of Stratton-Chu, I also found that a phase factor is necessary to solve it but my mates not always agree with me. Your advise is really helpful for my work. I will look at it to if there is a difference between my factor and that factor. Thank you again.

Yes! From the math structure of Stratton-Chu, I also found that a phase factor is necessary to solve it but my mates not always agree with me. Your advise is really helpful for my work. I will look at it to if there is a difference between my factor and that factor. Thank you again.


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Posted: 1 day ago 17 set 2025, 14:21 GMT-4

I recommend you study the example model: "microstrip_patch_antenna_periodic" in the Comsol-supplied Application Library. "Modeling of a Phased Array Antenna" Application ID: 88011 . See https://www.comsol.com/model/modeling-of-a-phased-array-antenna-88011 . Be sure to read the discussion of how the far field computations are done in the associated .pdf file. You need to apply an array factor.

I want to know the factor af3() could be. I think it should be a complex number. But from the document, it seems a real number. Is there a source of the array factor?

>I recommend you study the example model: "microstrip_patch_antenna_periodic" in the Comsol-supplied Application Library. "Modeling of a Phased Array Antenna" >Application ID: 88011 . See https://www.comsol.com/model/modeling-of-a-phased-array-antenna-88011 . Be sure to read the discussion of how the far field computations are done in the associated .pdf file. You need to apply an array factor. I want to know the factor af3() could be. I think it should be a complex number. But from the document, it seems a real number. Is there a source of the array factor?

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Posted: 24 hours ago 17 set 2025, 14:32 GMT-4

I get it. They are totally the same.

I get it. They are totally the same.

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Posted: 22 hours ago 17 set 2025, 16:06 GMT-4

I recommend you study the example model: "microstrip_patch_antenna_periodic" in the Comsol-supplied Application Library. "Modeling of a Phased Array Antenna" Application ID: 88011 . See https://www.comsol.com/model/modeling-of-a-phased-array-antenna-88011 . Be sure to read the discussion of how the far field computations are done in the associated .pdf file. You need to apply an array factor.

So if I want to apply this factor and calculate far field in Electromagnetic Waves, Transient. I think I need to multiply this factor in different frequency in far field node in Electromagnetic Waves, Transient. How can I achieve this?

>I recommend you study the example model: "microstrip_patch_antenna_periodic" in the Comsol-supplied Application Library. "Modeling of a Phased Array Antenna" >Application ID: 88011 . See https://www.comsol.com/model/modeling-of-a-phased-array-antenna-88011 . Be sure to read the discussion of how the far field computations are done in the associated .pdf file. You need to apply an array factor. So if I want to apply this factor and calculate far field in Electromagnetic Waves, Transient. I think I need to multiply this factor in different frequency in far field node in Electromagnetic Waves, Transient. How can I achieve this?

Robert Koslover Certified Consultant

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Posted: 20 hours ago 17 set 2025, 18:24 GMT-4
Updated: 20 hours ago 17 set 2025, 18:28 GMT-4

Last I checked, the Comsol Multiphysics RF module doesn't (yet!) offer the user any built-in post-processing routine to compute/plot far-field radiation from time-domain/transient RF computations even for single radiating elements, let alone arrays of them. You can, in principle, write your own such routines, but you'll need to go back to fundamentals. I've done that in some rather specialized cases for my own use, so I know it is possible. However, I don't have any general-purpose routines to share here. Perhaps, if there is sufficient demand, Comsol's RF module development staff can be persuaded to create & add such a feature to the code? (By the way, if you have not studied / worked with modeling transient behavior of antennas before, you might want to review the literature on it. There are many new ways to get confused.)

-------------------
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
Last I checked, the Comsol Multiphysics RF module doesn't (yet!) offer the user any built-in post-processing routine to compute/plot far-field radiation from time-domain/transient RF computations even for single radiating elements, let alone arrays of them. You can, in principle, write your own such routines, but you'll need to go back to fundamentals. I've done that in some rather specialized cases for my own use, so I know it is possible. However, I don't have any general-purpose routines to share here. Perhaps, if there is sufficient demand, Comsol's RF module development staff can be persuaded to create & add such a feature to the code? (By the way, if you have not studied / worked with modeling transient behavior of antennas before, you might want to review the literature on it. There are many new ways to get confused.)

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Posted: 17 hours ago 17 set 2025, 21:49 GMT-4

Last I checked, the Comsol Multiphysics RF module doesn't (yet!) offer the user any built-in post-processing routine to compute/plot far-field radiation from time-domain/transient RF computations even for single radiating elements, let alone arrays of them. You can, in principle, write your own such routines, but you'll need to go back to fundamentals. I've done that in some rather specialized cases for my own use, so I know it is possible. However, I don't have any general-purpose routines to share here. Perhaps, if there is sufficient demand, Comsol's RF module development staff can be persuaded to create & add such a feature to the code? (By the way, if you have not studied / worked with modeling transient behavior of antennas before, you might want to review the literature on it. There are many new ways to get confused.)

Thanks for your reply! My idea is doing FFT - far field in frequency domain- doing IFFT. But I find their is already a Far-Field node in EW, Transient. Now I'm try to perform the convolution of FFT(array factor) in the time domain but I don't know if it works. I'm totally a green hand with COMSOL and I would be very grateful if you could offer an easy-going literature on transient.

>Last I checked, the Comsol Multiphysics RF module doesn't (yet!) offer the user any built-in post-processing routine to compute/plot far-field radiation from time-domain/transient RF computations even for single radiating elements, let alone arrays of them. You can, in principle, write your own such routines, but you'll need to go back to fundamentals. I've done that in some rather specialized cases for my own use, so I know it is possible. However, I don't have any general-purpose routines to share here. Perhaps, if there is sufficient demand, Comsol's RF module development staff can be persuaded to create & add such a feature to the code? (By the way, if you have not studied / worked with modeling transient behavior of antennas before, you might want to review the literature on it. There are many new ways to get confused.) Thanks for your reply! My idea is doing FFT - far field in frequency domain- doing IFFT. But I find their is already a Far-Field node in EW, Transient. Now I'm try to perform the convolution of FFT(array factor) in the time domain but I don't know if it works. I'm totally a green hand with COMSOL and I would be very grateful if you could offer an easy-going literature on transient.

Robert Koslover Certified Consultant

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Posted: 16 hours ago 17 set 2025, 22:40 GMT-4

I haven't tried that approach. I suggest you ask Comsol Support for specific suggestions about the best way to do this, especially in regard to including the array factor and/or any kind of periodic (or Floquet) boundary conditions. And before even attempting that, I would want to make sure a single element antenna was being handled properly. Take it one step at a time. https://www.comsol.com/support

-------------------
Scientific Applications & Research Associates (SARA) Inc.
www.comsol.com/partners-consultants/certified-consultants/sara
I haven't tried that approach. I suggest you ask Comsol Support for specific suggestions about the best way to do this, especially in regard to including the array factor and/or any kind of periodic (or Floquet) boundary conditions. And before even attempting that, I would want to make sure a single element antenna was being handled properly. Take it one step at a time. https://www.comsol.com/support

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Posted: 15 hours ago 17 set 2025, 23:33 GMT-4

Thanks for your advise!

Thanks for your advise!

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Posted: 14 hours ago 18 set 2025, 00:04 GMT-4

I think of my models again. My model don't need to take array effect into account, so I can just apply far field node in EW, Transient. The other model only need to see the far field spectra in normal direction where array factor equals to 0 for all frequency, so far field of single unit is same as far field of array. I can still just apply far field node in EW, Transient there to get the far field spectra of array in normal direction.

I think of my models again. My model don't need to take array effect into account, so I can just apply far field node in EW, Transient. The other model only need to see the far field spectra in normal direction where array factor equals to 0 for all frequency, so far field of single unit is same as far field of array. I can still just apply far field node in EW, Transient there to get the far field spectra of array in normal direction.

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