Re： <CST MWS> A periodic structure+Plane wave problems

---

Hi,
I'm glad that it works for you. The diffrences you see can be the result of many things like solver settings, mesh setting etc.
If you'll post your model and the article you are trying to follow i'll be able to give it a dipper inspection.
rgdz,
P.

hi pushhead
thanks for your helpful comments.
i am attaching my simulated model along with the paper with which i am comparing my results. i am getting the resonance frequency at 11.7ghz while in paper for the same structure resonanct frequency is at 10.8ghz.
have a look at it and let me know if you find some clue .
thanks
shahid78

Hello,
I have reviewed your model and the paper.
First of all, please make sure that you have modeled the shorting pin in the middle correctly. It seems like its material is er=2.2 instead of PEC.
Also,I think that in the paper the use their own FDTD codes instead of a commercial software package. Considering that, your results are "just" 8% higher in frequency than theirs.
Rgdz,
P.

hi pushhead
thanks for reviewing my model and helpful comments.yah u were right the material of central pin was not pec however when i changed it to pec i got the same result i.e resonant frequency at 11.7ghz.
also one other question have u tried this method with uc ebg because i got error message when i tried to simulate it using this method
the error message is pec material is touching the boundary
i dont know why i m getting this error message.
looking forward for your helpful comments
thanks

Hello again,
I have tried uc ebg in the past and didn't get any error messages. I'll check it out sometime soon and see if there are any "traps" there.
Regarding your model, I've taken another (deeper) look into it and into the paper noticed several things:
1. In the paper they don't mention anything about the metal layer thickness or the shorting pin radius. I did some sweeps and found that resonance changes along with pin radius and metal thickness. Check out the attached picture for metal thickness sweep:

2. The paper uses Periodic Boundary Conditions, whereas in this case you use E/H boundaries.
3. Just to be on the safe side, set the energy level to -50 dB or more so that your S-parameters converge properly (-30 dB wasn"t enough in your case)
4. See if you can get a paper that icludes calculations and actual manufacturing and measurements of EBG structures. This would be the best way to test the accuracy of your model.
Regards,
P.

hi pushhead
thanks for giving some time to resolve my problem
yes you are right by changing the pin radius the resonant frequency changes and i have found that resonant frequency decrease with decrease in pin radius however when radius approaches 0.1mm after that there is no significant change. and for 0.1mm radius my simulated resonant frequency is 11.2ghz so i was not able to approahe the paper resonant frequency of 10.8ghz
h
regarding ucebg simulation i tried this method but when i use E and H boundary conditions for the model the E boundary touches the PEC of the UC EBG cell and cst gives error message for this.

i will be waiting for your reply regarding ucebg simulation using this method.
thanks a lot

some people uses the waveguide method but the problem si not the same:
with a plane wave you use periodic conditions in ±x and ±y. So you have an infinite substrate in both directions.
However, with the waveguide method, the diagram simulate is for an infinite row of EBG cell.
So that's not totally the same thing.
Don't you think so ?

salam shahid
are you could simulate the PMC in cst?
if yes please tell me as soon as possible

hello
well i tried my best to find a way to model PMC structure in cst but as far as i know its not possible in cst

all you can do is to use magnetic boundary condition to simulate PMC
this is all help i can offer at this time
regards

I'm gonna prepare a thesis about reflectarray with microstrip patch element .I'm supposed to simulate it with CST.
Since I think some of you have worked through the reflec array I wonder if I could ask you to guide me through the periodic structures . I have desined a microstrip antenna with T-solver . But I need to know a little about how to use from the unit cell.
But I have not enough info about making n*n structures .
I look forward to hear from you soon .
Thanks in advance