[SOLVED] CST - "Calculation domain filled with metal (PEC)"

Hello,

Last Couple days im playing with CST Microwave Studio, doing my best to learn how to use it. Unfortunatelly, often im experiencing strange and impossible to solve (as for me) problems. Im trying to design my first own antenna - patch, and in fact i had to start already 3 times from scratch because solver complains about some imagined errors, like complaining about wrong discrete port edge when theres no any discrete port in project anymore, or shouting about wrong port design when all what i did was adding some needed holes in groundplane without touching existing (and working previously) ports...
Now i do have next problem: "The calculation domain is filled completely with metal (PEC). Please check background material settings and layer prosperities". This error is really frustrating, no matter what i do - its still present. Incrasing mesh prosperities, changing port design, even deleting all PEC objects - nothing does work.
Right now for example i have my waveguide port designed incorrectly, previously (in my first or second attemot to this antenna) with such design solver complained about need of at least 3 mesh cells, now he dont care about amount of mesh cells, instead souting all time about "calculation domain filled with metal". Can somebody experienced with CST check my design and try to find out what exacly is going on and what im doing wrong ?

Thank you very much for any help.
Greg

View attachment Simplepatch2_1280_50_Hard.rar

sigreg said:

Hello,

Last Couple days im playing with CST Microwave Studio, doing my best to learn how to use it. Unfortunatelly, often im experiencing strange and impossible to solve (as for me) problems. Im trying to design my first own antenna - patch, and in fact i had to start already 3 times from scratch because solver complains about some imagined errors, like complaining about wrong discrete port edge when theres no any discrete port in project anymore, or shouting about wrong port design when all what i did was adding some needed holes in groundplane without touching existing (and working previously) ports...
Now i do have next problem: "The calculation domain is filled completely with metal (PEC). Please check background material settings and layer prosperities". This error is really frustrating, no matter what i do - its still present. Incrasing mesh prosperities, changing port design, even deleting all PEC objects - nothing does work.
Right now for example i have my waveguide port designed incorrectly, previously (in my first or second attemot to this antenna) with such design solver complained about need of at least 3 mesh cells, now he dont care about amount of mesh cells, instead souting all time about "calculation domain filled with metal". Can somebody experienced with CST check my design and try to find out what exacly is going on and what im doing wrong ?

Thank you very much for any help.
Greg

Click to expand...

Hi

I have not done anything more than take a very quick look at CST - little more than opening it up, and closing it down. But I did watch a video on using it for antennas, and I do have experience of HFSS, so perhaps these comments might be useful. But I'm sure someone with more CST knowledge can add to them, or correct me if I'm wrong.

In HFSS at least, the program initially assumes everything is a perfect electrical conductor (PEC). So if you draw a dipole made of metal, and add a port, since the whole thing is surrounded by a perfect electrical conductor (PEC), you can't get any results from it. Everything is shorted out. With HFSS, one draws what Ansys refer to as an "airbox" around the antenna. This is a region of vacuum, so the components of the antenna are no longer shorted by the PEC.

I think you will find you need to do similar in CST. But in the CST video I see, when starting a new project, there were options for CST to create a project of the sort you wanted. One or more of those was an antenna. So when antenna was selected, the region of vacuum was automatically put in place. The size grew automatically as the antenna size was changed.

So I suspect your problem is you need a box around your antenna made of vacuum, and some boundary attached to that. But I think CST can do that automatically for you, whereas HFSS does not.

In the short video of CST that I see, it looked quite easy to create a simple antenna and simulate it - far simpler than in HFSS, where one has to create the airbox manually, work out its size and add a "radiation boundary" to it.

Sorry, I can't be of any more help, as I don't use CST, but hopefully I may have given you a clue what your problem is.

Deborah

sigreg said:

Now i do have next problem: "The calculation domain is filled completely with metal (PEC). Please check background material settings and layer prosperities".

Click to expand...

Background material is the material that fills the simulation volume, where you have not drawn anything else.
For antennas, this must be air. It seems that you have set perfect conductor (PEC) instead.
Check the setting for the background material, as the message told you.

Deborah, Volker, of course youre right At start of each new project CST ask about type of antenna what will be designed, last time i skipped it (canceled without answer) as i was sure my choice does have influence only for default units in new project. Looks like it does not, not only. There is something like "background material" (i never played with it before) as you said, and default material is set to PEC (when i was sure default would be vacuum, air or other type of free space). Also boundary box by default is set in other way than rookie like me would expect.
Generaly - problem is solved. I had to check and change background material (what i never did before) and also set up correctly boundary box. Now everything is working fine, thank you very much for your help !

Greg

volker_muehlhaus said:

Background material is the material that fills the simulation volume, where you have not drawn anything else.
For antennas, this must be air. It seems that you have set perfect conductor (PEC) instead.
Check the setting for the background material, as the message told you.

Click to expand...

I have change the setting to 'Normal', but it's still not working

sigreg said:

Deborah, Volker, of course youre right At start of each new project CST ask about type of antenna what will be designed, last time i skipped it (canceled without answer) as i was sure my choice does have influence only for default units in new project. Looks like it does not, not only. There is something like "background material" (i never played with it before) as you said, and default material is set to PEC (when i was sure default would be vacuum, air or other type of free space). Also boundary box by default is set in other way than rookie like me would expect.
Generaly - problem is solved. I had to check and change background material (what i never did before) and also set up correctly boundary box. Now everything is working fine, thank you very much for your help !

Greg

Click to expand...

I also have a same problem like you. How do you solve the problem? I also set the background material as normal but it still not working. How do you create the boundary box?
Thank You