Jump to content
  • Announcements

    • Rahul Ponginan

      Please click here for a short but important announcement   03/26/17

      Dear Users Our Commercial and Academic users around the world can use these same forums here as before i.e. the Altair Support Forum , Commercial users from India with solver queries can go to the Solver Forum for India Commercial Users , Academic Users from India and AOC India Participants are requested to go to the Forum for India Academic Users and AOC India Participants , We will be tending to all queries in all the forums promptly as before, thank you for your understanding. 
Taram

Using symmetry for modeling simple array

Recommended Posts

__Hi everybody.

1. I am trying to use magnetic symmetry to model simple 2 element array (see image and 1.cfx file below). But FEKO 7.0-238289 (we have such license) gives me an error (i've attached image). Can anybody explain me, where is my mistake. User manual tells, that it is possible to model such structure, if "geometry to be meshed does indeed adhere to
the specified model symmetry (both geometric symmetry as well as symmetry of excitation and
loads where magnetic/electric symmetry is used)"

2. Another question. I calculate magnitude of active reflection coefficient for 2-port circuit in POSTFEKO by summation

 mag( REAL(S11)+REAL(S12) +i*(IMAG(S11)+IMAG(S12)) ) .

Now assume there are 10 ports :D. Is there any other way to find Active S parameters (or active VSWR)?

1.cfx

Geometry.png

Errors.png

Share this post


Link to post
Share on other sites

Hello Taram

 

4 hours ago, Taram said:

But FEKO 7.0-238289 (we have such license) gives me an error (i've attached image)

This s a really old version (in my opinion). The oldest I have installed on my system currently is 2017.0. Please try to upgrade.

 

4 hours ago, Taram said:

Can anybody explain me, where is my mistake.

The problem in your model is your S-parameter request. The request that you have is for only one of the ports. The resulting model would excite the port, but not the other port and thus your excitation contradicts the specified symmetry. Even if you add the other port to the S-parameter request, you will run into the same problem, since it will excite one port and load all the other ports, then excite the next port. In this process, the symmetry is violated (exciting the one side of the symmetry plane, but not the other).

 

I'm not sure why you are using symmetry on such a basic model, but maybe it is just and example. If you want the mesh to be symmetrical, then use geometrical symmetry and you won't run into the problem.

4 hours ago, Taram said:

2. Another question. I calculate magnitude of active reflection coefficient for 2-port circuit in POSTFEKO by summation

 mag( REAL(S11)+REAL(S12) +i*(IMAG(S11)+IMAG(S12)) ) .

If you want the active reflection coefficient, simply excite all the ports that you would like to have active an look at the reflection coefficient at the port of interest. I'm not sure what you are trying to calculate with the equation above.

 

If you do have a model with 10 or 100 or more ports and you want to add the reflection coefficients in some way, I would use the scripting feature (I can't remember if it is available in version 7.0, but I suspect it might be).

Taram likes this

Share this post


Link to post
Share on other sites

Hello JIF. First of all, Thank you very much for your answer.

 

1.

On 13.02.2018 at 10:42 PM, JIF said:

This s a really old version (in my opinion). The oldest I have installed on my system currently is 2017.0. Please try to upgrade.

__Of course, you are right. I hope we well upgrade this version as soon as possible. Unfortunately, it depend not only on me. 

2.

On 13.02.2018 at 10:42 PM, JIF said:

I'm not sure what you are trying to calculate with the equation above.

__I want to calculate active reflection coefficient Ra, i.e. reflection coefficient, that takes into account energy, that goes to current port from neighboring ports (due to mutual coupling). 

For exhample, when we solve unit cell of infinite array  with periodic boundary condition we obtain Ra. This model automatically accounts mutual cuopling and i don't need to add complex function's by myself. 

__For 2-port network (1 port) active reflection coefficient

Ra1=(S11*V1+S12*V2)/V1={if all incident field  amplitudes and phases is equal}=S11+S12; (where all function's are complex).

__In POSTFEKO i have to write Ra1="abs( REAL(S11)+REAL(S12) +i*(IMAG(S11)+IMAG(S12)) ) ".

__If i need active VSWR (Wa), then in POSTFEKO i must write 

Wa=( 1+ abs( REAL(S11)+REAL(S12) +i*(IMAG(S11)+IMAG(S12)) ) )/(1-abs( REAL(S11)+REAL(S12) +i*(IMAG(S11)+IMAG(S12)) ) );

__For 3-port network in case of equal incident field amplitudes

Ra1=S11+s12+s13;

__In POSTFEKO - Ra1="abs(  REAL(S11)+REAL(S12) +REAL(S13)+i*(IMAG(S11)+IMAG(S12)+IMAG(S13) )  ) ".

Wa=....

__I tried to clear for you, what i meant. As far as i understood, there is no built-in functions to calculate Ra and Wa in FEKO 7.0-238289 .

But may be this useful function available in newer versions of FEKO?

On 13.02.2018 at 10:42 PM, JIF said:

I would use the scripting feature (I can't remember if it is available in version 7.0, but I suspect it might be).

__Ok. I heard about it, but never used. I prefered CADFEKO and POSTFEKO gui :)). I think it's time to begin to study scripting in FEKO. 

 

3.

On 13.02.2018 at 10:42 PM, JIF said:

I'm not sure why you are using symmetry on such a basic model, but maybe it is just and example.

__Of course real model is more complicated. But i attached here this simple model to show you a problem i stuck on (without of irrelevant geometry). More correct 16 dipoles with ground (look at image with16 dipoles below). There is no dielectric here, but in future dipoles may be on PCB. Of course the first thing, that occurred to me - was to use electric and magnetic symmetry here to reduce memory requirements and computation time. Of course, S11 of full model and S11 of quarter of full model are not the same (take a look at my image "S_parameters_relation__.png"). But both model allows me to find necessary Active_S11. So for example, i can optimize smaller model to minimize Active_S11, Active_S22, Active_S33 and Active_S44.

 

 

It is sound and logical to use symmetry here. It would be great, if it were possible to reduce model size with such a way.

__Am i correct, that (sadly) i can't do it in my version of FEKO?  May it is possible in newer versions of FEKO? If not can you tell FEKO team to work on this.

 

On 13.02.2018 at 10:42 PM, JIF said:

use geometrical symmetry and you won't run into the problem

__Good idea, but...

"Geometric symmetry does not reduce the number of unknown coefficients in the current basis
functions. Therefore there is no reduction in memory usage. There is, however, a reduction in
computation time when the matrix elements are determined.."

__So geometrical symmetry does not allow me to reduce memory...

 

 

 

5a841d9fcbd0e_16dipolesarraywithsym__.png.f454b553906a8af56aff207bf835b96c.png5a841d9ad9aa2_Original16dipolesarray__.png.b0fc4810eb0ee93d38206495a56c4cbb.png

 

 

S_parameters_relation__.png.1cf7761bdca5f8d4303ce20c227f5730.png

 

 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×