pec versus periodic boundary

hi piboo,
I am having CST 2006B installed in one of the lab PC so i can use this macro. Macro is embedded in top right corner of PPT. you can activate it by double click on it.
I am still not able to generate exact phase diagram as given in Samii's "Reflection phase characterization of EBG" by both macro and WGA method. I am not sure we getting correct answers by any method.

hi prafuldeo,

I think you will never find the same results as Samii's paper with CST MWS: R. Samii use a FDTD method and CST use a FIT method, that's not the same. So there will always few differences between the two methods.

With the macro I obtained the same curves but the frequency of non dephasing (don't know if it's like that to translate: phase = 0°) is shifting of 1 GHz.

The best way to check it, is to do some measures :P

Hi piboo,
I've attached the .cst file of samii's unit cell for 12Ghz resonating frequency. I've calculated the reflection phase by both the methods and results are also attached here. As you can see both results give fairly same results but none of them matching the original published results. If you are saying that results from FDTD is different from FIT then which one is more correct? As you can see for original results phase crosses zero degrees around 17.2 Ghz but with my simulation around 30 degrees at 18 Ghz. I am not convinced with the results. Also can you send me the dispersion diagram settings as given in sivenpiper paper for this model?

Regards
Praful

Hi,

I don't know which method is the best. I think a measure is the best way to check :p

I have the same results as you with CST. But if you try with a PEC or PMC you have good results.

I post the dipersion diagram in the next topic.

Also can you send me your email (in private message if you want) plz ?

I've tried macro and WGA method over PEC but i was not able to check it with PMC. how did you check it with PMC?

To check for a PMC you can design a square pec with periodic boundaries on x and y in zmin choose PMC, zmax open/open add space

But in local mesh properties you have to uncheck the box "Consider for ..." so when you start the simulation, the pec will not be consider so you will just only have a vaccuum box with a PMC boundaries at the end.

Do you understand ?

kind regards

hi piboo
well if at the end you need vacuum box then whats the purpose of modeling PEC why not just model vaccum box and use the required boundary conditions for PMC


regards

just if you want to check for pec just after :p
no need to create another model :)

I did it with vacuum box. But to get phase nearly equal to zero we have to keep the thikness as low as possible. And by comparision, macro method seems to be more sensitive than WGA method

yes.

For a pec I consider always a model in 2D. I don't use vaccuum box (for WGA method) because the background is normal, so no need to use it.

how we could simulate a pmc slab in cst?

Hi

I downloaded macro for calculate reflection phase, but i don′tknow how I used it, I copied it to macro CST MWS directory but I don′t know how run it...Can me everyone give instruction...?thanks very much

m.

Hi abdoeng

i was looking at your uplaoded model for WGA method.
i dont understand the following points:

1: why you are using waveguide port as well as farfield source?

2: how you get this graph of phase vs length?

3: and also what is this length? as i cant see any variable defined in your model file?

i hope you will understand what i am asking.

thanks

hi prafuldeo


you mentioned vaccum model , what do you mean by that ?
did you use macro or WGA method to simulate PMC reflection diagram.

thanks

Hello Shahid,
Since WGA method is much quicker and its easy to do parameter sweep with WGA method, I use this only. But I always cross check the final results with macro method for accuracy and till now I am getting same results with both so any method will do.

Regards

Hi everyone,

I have a problem. I am simulating a FSS cell in CST Studio and I want to calculate the reflection coefficient in a frequency range with a plane wave (TEM mode). I am using a waveguide, but I am not sure which mode I am exciting with a waveguide. Any of you can you tell me how to excite a TEM mode with a waveguide port.

Thanks in advance,

David

you have to check the ports E and H fields on both ports. and check the validation of TEM mode

hi praful. i think this file cannot run using cst 2010.did u have the reflection_macro that compatible with cst 2010?
thanks
yana-