Error when using FEKO solver for CMA

Zakaria

hi, i am trying to get the CMA of a wire antenna loaded with resistance and this error message appears'Characteristic mode analysis cannot be used when the number of MoM basis functions is zero'. Can any one tell me what does this error means and how to solve it. 

THANKS

Altair Forum User

Hi Mohammed,

 

Can you attach the model?  It will make it a lot easier to see what's happening.

 

It sounds like you don't have a valid mesh for the dipole.  How long is the dipole and at what frequency are you performing the simulation?  What is the wire radius?  You can also compare your model to the Examples Guide model ('A-1 Dipole example') and see if anything stands out.

Zakaria

thanks andries for replay, attached my wire design.

 

Unable to find an attachment - read this blog

Altair Forum User

Hi Mohamed,

 

Thanks for the model.  There are a few things that could explain why you're not seeing the characteristic modes in the attached model:

• The model doesn't contain any geometry.  There is only an infinite ground plane and a cable instance, both of which are approximations that can be used instead of complex geometry.  For characteristic modes, a model that will be solved using the Method of Moments (MoM) is needed.  In other words, there typically needs to be CAD that can be meshed into triangles and wire segments.
• The ports for the model are both Finite Element Method (FEM) line ports.  FEM is a separate solver from MoM and doesn't support characteristic mode analyses. 
• Neither port is excited or connected to anything.

I recreated what I think the model is trying to do (see ) using MoM.  Note that you need to add the requests that you are interested in; at the moment only the characteristic mode eigenvalue data is being calculated.

 

Are you trying to reproduce results from an article/measurements/calculations?  Do you have any reference data?  Without further information, this is as far as I can go.  I would urge you to go through the Examples Guide and some overview documents on the website:

• https://altairhyperworks.com/ResourceLibrary.aspx?keywords=Characteristic&altair_products=FEKO

Unable to find an attachment - read this blog

Zakaria

thank you very much. sorry, i am using FEKO 14.0.411 but i can not open your attached file

thanks again

Altair Forum User

Hi Mohamed,

 

I don't think I have a compatible version anymore.  If you run  though, then the script should rebuild the model from scratch.  To run the script, just drag and drop it into CADFEKO and click on the run button.

Unable to find an attachment - read this blog