reflection phase diagram of ebg/pbg surface using CST

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shahid78

Joined: 29 Jul 2006
Posts: 328
Helped: 28

24 Jul 2007 11:34 ebg pbg

i am trying to find the bandgap of ebg structure using reflection phase diagram method. i am using CST MWS 2006B.

i model the unit cell of the ebg strucuture and then illuminate it with the plane wave and set up the probe to record the phase of the reflecing singal.

but i cant get the expected result. can any body tell me whether this method is correct and if correct what mistake i am making and if someboday know what other method i can use to find the bandgap of PBG/EBG structure using CST.

iaia

Joined: 26 Sep 2007
Posts: 48
Location: Italy

30 Sep 2007 12:50 pbg phase diagram

shahid78 wrote:

Hi, have you solved your problem? I'm trying to simulate the phase of the reflection coefficient but I have some problems with the boundary conditions. Can you help me?
[/quote]

shahid78

Joined: 29 Jul 2006
Posts: 328
Helped: 28

01 Oct 2007 11:06 cst pbg unit cell

hi

well you have to model 3 structures .

1 PEC model
2 vaccum model
3 actual model

and then use macro to find the reflection phase diagram.
can you explain a bit what boundary problem you are talking about,

regards

iaia

Joined: 26 Sep 2007
Posts: 48
Location: Italy

01 Oct 2007 11:22 Re: reflection phase diagram of ebg/pbg surface using CST

Hi,
I have posted my CST file yesterday. I have a unit cell (a square mushroom-type geometry) and I have selected periodic boundary for xmin, xmax, ymin, ymax, open boundary for zmax and Et=0 for zmin. I have used the plane wave excitation, but in this way the phase of the reflection coefficient does not appear in the results. So I used a waveguide port , but the resulting phase has a strange behavior (with a discontinuity roughly corresponding to the resonance frequency instead of crossing for 0°). This is the first time I use CST, but I did not have any problems with doing the same simulation in Designer.
Thanks a lot.

shahid78

Joined: 29 Jul 2006
Posts: 328
Helped: 28

02 Oct 2007 11:28 Re: reflection phase diagram of ebg/pbg surface using CST

well i dont think u can use waveguide port with periodic boundary conditions.
so i think you should use plane wave exciation for periodic boundary condition in x and y direction and Et=0 at Zmin and open at Zmax.

and then you can use macro to find the reflection phase diagram

regards

abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

03 Oct 2007 4:49 reflection phase diagram of ebg/pbg surface using CST

hi iaia,i already simulate mushroom using cst
what is ur request
send email to me,ok
regards

sassyboy

Joined: 20 Sep 2003
Posts: 88
Helped: 14
Location: United Kingdom

03 Oct 2007 11:11 Re: reflection phase diagram of ebg/pbg surface using CST

Make sure that you use the "Unit Cell" boundary condition instead of the "Periodic" boundary condition.

In the pre-2006 version, yes, we used macros, but this is no longer necessary in 2006B, it is also straightforward too. What you have to do is to have an additional model of just the PEC groundplane with a thickness equal to that of the overall thickness of the EBG structure. In the end you are left with two phase plots, one corresponds to EBG and the other corresponds to a referece PEC slab. Use excel and carry out a phase comparison and the result is the reflection phase.

shahid78

Joined: 29 Jul 2006
Posts: 328
Helped: 28

03 Oct 2007 11:32 Re: reflection phase diagram of ebg/pbg surface using CST

hi sassyboy

the method which you are talking seems to be interesting.
can you please tell which port you are using with unit cell boundary condition
or you are just using plane wave excitation

thanks

iaia

Joined: 26 Sep 2007
Posts: 48
Location: Italy

04 Oct 2007 9:50 Re: reflection phase diagram of ebg/pbg surface using CST

Hi all,

this is my cst file. I have set the boundary conditions as above and used a plane wave excitation, but when i tried to use the macro for the S parameters I got an error: "array lower bound is larger than upper bound".

Please, help me!!!
Crying or Very sad

Ps: I am using CST 5.0.1, but I'll get CST 2006b within few days.

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qqqooo

Joined: 06 Oct 2006
Posts: 18

05 Oct 2007 5:11 reflection phase diagram of ebg/pbg surface using CST

thanks

abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

06 Oct 2007 13:05 reflection phase diagram of ebg/pbg surface using CST

hi all,i try to simulate ebg model using ansoft designer and cst with the above technique of sassayboy
the results so ggod in both cases
i use cst 2006b,avoiding using periodic walls,plane wave and macro files
regards

iaia

Joined: 26 Sep 2007
Posts: 48
Location: Italy

08 Oct 2007 11:47 Re: reflection phase diagram of ebg/pbg surface using CST

Hi abdoeng,
I'm still having problems with my simulations in cst, can you tell me the details of your model?
Thanks a lot

abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

09 Oct 2007 10:27 Re: reflection phase diagram of ebg/pbg surface using CST

hi iaia,sorry for my lating reply aas u email me
also for shahid,here my reply:
1-i build my model normaly,ok,
2-then use electric walls in -x,+x
3-biulding magnetic walls in -y,+y
use waveguide port in top of structure
(use embedded port from waveguide port to the upper point in mu structure)ok
then see argument of s paprameters
that all
u ask why e walls in -x,+x as to guide the electric filed that is polarized in x direction as u know

i hope it help

Added after 28 minutes:

here my model

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09 Oct 2007 10:27 Ads

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iaia

Joined: 26 Sep 2007
Posts: 48
Location: Italy

10 Oct 2007 9:56 Re: reflection phase diagram of ebg/pbg surface using CST

Hi abdoeng,
it works!!! Just an other question (so far Very Happy

): with this setup can I simulate a oblique incident plane wave?
Regards

shahid78

Joined: 29 Jul 2006
Posts: 328
Helped: 28

10 Oct 2007 11:13 Re: reflection phase diagram of ebg/pbg surface using CST

thanks abdoeng for your explanation of the problem.

however your method is a little different then sassyboy.

you are constructing only the actual model and then observing the argument of s parameters whereas sassyboy is constructing 2 models one the actual model and another PEC model with the same overall thickness. and then sassyboy is exporting the data of the 2 models and compare in excel to find reflection phase.

so i am confused which method is accurate yours or sassyboy.

any comments on this would clarify my doubts

thanks

abdoeng

Joined: 22 Feb 2004
Posts: 685
Helped: 14
Location: EGYPT

10 Oct 2007 11:25 reflection phase diagram of ebg/pbg surface using CST

akhy shahid,the method i test is correct that i compare that result with ansoft designer
so u can test them if u not sure my result is correct
regards
iaia,that method,i don't test it for any oblique angle,i so sorry,could u try it,i easy can do that but in ansoft designer,not in cst
regards

iaia

Joined: 26 Sep 2007
Posts: 48
Location: Italy

10 Oct 2007 11:36 Re: reflection phase diagram of ebg/pbg surface using CST

Hi abdoeng,
Ok, I will try.
I have seen some other posts where you talk of dispersion diagram. Have you already tried to get it for the mushroom-type structures? Can you please send me some examples? It would be of great help for me.
Thanks a lot Very Happy

vulehuy93

Joined: 27 Apr 2008
Posts: 2

04 May 2008 5:57 Re: reflection phase diagram of ebg/pbg surface using CST

Hi all,
I'm using CST2006. Which macro do I have to use to calculate the phase of reflection
coefficent?
This is the first time I use CST.
Please tell me in detail.
Regards

prafuldeo

Joined: 26 Mar 2008
Posts: 153
Helped: 10
Location: UK

04 May 2008 8:02 reflection phase diagram of ebg/pbg surface using CST

Hi vulehuy93,
Go to the link below and you will get the ppt name PBG_Reflection_method. Download it and run the macros. Everything is explained in that macro.
http://www.edaboard.com/ftopic304618.html
Hope it helps.
Regards
Praful

vulehuy93

Joined: 27 Apr 2008
Posts: 2

06 May 2008 6:13 Re: reflection phase diagram of ebg/pbg surface using CST

I downloaded that macro but I can't use it.
After unzip file reflection_macro, I have file reflection-method.bas
I copy it to make a macro in CST.
But when I use it for 3_hexa_structure_pec_01, the result is strange
My screen when I use macro

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prafuldeo

Joined: 26 Mar 2008
Posts: 153
Helped: 10
Location: UK

06 May 2008 13:59 reflection phase diagram of ebg/pbg surface using CST

Dear vulehuy93,
The results you showed is for PEC and as you can see it is showing 180 degress for all the frequencies as expected. To get the desired results do as follows:
1. make a unit cell with all the original dimensions but take all material as vacuum. In probe results look for argument and note the phase for maximum frequency.
2. now make original unit cell with all material as PEC and then simulate.
3. Lastly, simulate the unit cell with all original materials. Run the macro provided in this simulation and fill the Fmin, Fmax, phase value which you noted for vacuum simulation and PEC simulation file name. Run the macro and if you entered everything correct, you should get the desired result.
PS- Make x-y as periodic and keep Zmax=open add space, Zmin=electrical except for vacuum case where Zmin=open

Hope it helps.
Regards
Praful