# Need help with structure in CST Microwave studio

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#### eirp

I have question for members experienced with CST MWS. Structure is attached - it crashes during "Normal matrix..." initialization. It's strange because SPK3 - similar structure made by the same generator is analysed without any problems.

Eirp

#### Kit-the-great

##### Full Member level 3

I don't know: it's bug of MWS or bug in Sierpinsky triangle generator, but in Your case: move all importXX objects to 'Ground' layer; on my CST-MWS 3.2 this bug in Your project has been vanished after this procedure.

Have a nice day !

Kit-the-great

#### eirp

Dear Kit-the-great!

Thank you very much for your goodwill, but problem persists still.. I've moved imported objects into layer 'Ground' as you suggested and it crashed in y-plane again.
Please, can you send me your repaired file via e-mail, we can check where is the bug (I'm using CST-MWS v3.4); my e-mail sent to you by PM.
Thanks again,
best regards,
Eirp

#### JNovak

##### Junior Member level 1
re

Not sure if this helps Our company made extensive attempts to simulate all the fractal patterns related antennas Koch, Serpinsky etc. Using many of the tools, like CST, Microwave Office, Zeland etc etc. However the experimental measurement results proved that apparently all these packages do not work for this kind of fractional dimension geometries.

#### jjantenna

##### Member level 2
I think the problem should be the the connect joint between Serpinsky and coaxial inner conductor. Transit part should be added between.
Another point, all triangles in your model are point joint! It's unrealistic and may introduce error.

#### hca41316

##### Newbie level 4
I think the problem is the thickness of the metal...

You can speed up your simulation if you starts from f=0GHz, you need only the half time (fourier!)

Hmm, isn't there a magnetic wall in zx-plane? With wall, simulation works!

hc

#### eirp

Hi, all!

Thank so much for your time... I'm now very busy and on tuesday I'm going away for a week. Very shortly now

- start from 0GHz - it's a good tip!
- there isn't magnetic wall but I'll try to add - symmetry
- the problem really seems to be in the connecting coax/Sierpinsky

BTW how to remove joint points?

Because I really need to simulate this structure (I've made it and I want to compare), I'll start to work with CST again when I return. Your hints are very helpful :lol: :lol:
Many thanks for collaboration, I'll inform you about progress.
Best regards,
Eirp

#### jjantenna

##### Member level 2
You are on the right track, eirp!
The problem is in the connecting coax/Sierpinsky. Setting the zy-plane as magnetic wall and changing Zmin to Open(add space) seem to solve your problem.

#### jjantenna

##### Member level 2
What's your test result? It is something like this?

#### eirp

Dear Jjantenna and others!

Finally I've test it again with magn. wall and really, it works!!!
I have only SPK4 on GIL substrate at this time. I must mount it on ground plane, so it isn't measured yet. I'll post results here when it will it be done.
It's about 25cm high and I expect 4 bands starting around 0.7GHz.
Presented structure is smaller (height 90mm) version which probably works on ~2,4,8,16 GHz.
Again, thanks for your great support, you help me so much :lol:
Best regards,
Eirp

#### jjantenna

##### Member level 2
eirp,
You'd better add the GIL substrate on the back of the dipole in your model, for the dielectric constant (yours value?) changes the resonance freq.
If possible, post your spk3 here. I want to see the difference between 3 and 4. Why should the mang.wall be added?
I also interested in your Sierpinsky Generator. I think some improved is required, just as I mentioned in previous post. The connecting part between Sierpinsky is the EDGE! How about connecting point like this?

#### eirp

Hi jjantenna,

Of course I know about substrate, I add it in next evolution phase. It can be done now when simulation runs.
SPK3 is as attachment, name means Sierpinski triangle iteration #3 (iteration #0 is the main triangle without holes - 1/2 of BOWTIE antenna).
I don't know exactly why, but simulation runs when magnetic wall is present + it reduce computing time.
My generator can make connections between triangles by point or by small connecting triangle-see picture. This is necessary when IE3D is used. In FDTD there is specific mesh and point is a small box anyway.
PM me your e-mail for sending the generator, it's strange program in Pascal but works...
Eirp

#### floggie

##### Newbie level 3
C$T MW$ 4.2 problem

hi all,
i'm using c$t mw$ 4.2 with 4.1 patch, everytime when i undo a structure drawing or using structure history, the program crash. please help. anyone has the similar problem. thanks

flog

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