cst dispersion diagram

Hello,
I am trying to generating a dispersion diagram of a EBG for determining its band-gap on CST 2008(MWS). I want to get a dispersion diagram as shown(Fig. 10) in ?High-Impedance electromagnetic surfaces with a forbidden frequency band,? by D. Sievenpiper.
Does any one knows the procedure to obtain it in CST MWS?
Thanks in advance.
Praful

You have to use the eigenmode to plot the dispersion diagram

hi piboo

do you have any solved cst mws example of eigen mode solver to generate dispersion diagram.
it would be helpful if you post any example

thanks

Hello

to plot the dispersion diagram you need the following boundaries conditions:

±x periodic boundaries
±y periodic boundairies
± electric boundaries

then always in the boundaries conditions, if you have selected periodic boundaries, you will have a new slot : "Phase Shift/Scan Angles"
In the text box x and y: you put a variable like phase which inits to 0.

Then you lauch the eigen solver.
Parameter sweep
New Sequence
Choose the phase variable and choose sweep from 0 to 180.
Add watch: Frequency of Mode 1 & Frequency of Mode 2.

Now start and it will plot your absorption diagram.

If you have a sievenpiper structure upload it and iI will configure it.

regards

piboo

hi piboo,
I'll also try this procedure and let you know about the results. By the way have you got the reflection phase diagram of a unit cell. I am not getting correct results for Samii's "Reflection Phase characterization" paper. Have you got matched result for this paper?

hi piboo
pls upload ur file of dispersion diagram here to be available to every one here
regards

hi piboo,
Are you able to generate all the dispersion results as given in Sivenpiper paper " High impedance surfaces" ?

Hello all,

this is the results as obtain for Sievenpiper structure, I will post the structure later (just have the results on this computer)

its requested to upload the strucute along with the paper if possible.

hi piboo,
which figure result is this Fig.7 or Fig.10?

This is the Sievenpiper structure simulate from R. Samii's paper:

"Reflection Phase Characterizations of the EBG Ground Plane for Low Profile Wire Antenna Applications"

I you look on fig7 of:
"High-Impedance Electromagnetic Surfaces with a Forbidden Frequency Band"
(you can see it at

https://www.edaboard.com/viewtopic.php?p=861078#861078 )

You can see there is good agreement.

I post the first paper and the structure (you will need CST 2008 sp 5 to open it).

regards

piboo

Hi piboo,
I saw your result, yours is frequency Vs Phase. In the paper it is Frequency Vs Wave Vector. Can you modify your model to the same scales?

Regards
Praful

hi piboo

whenever i use eigen mode solver to generate the dispersion diagrom of mushroom type EBG structure i get the following error message:

the lowest eigenmode frequency is greater than the upper frequency range limit. please check the frequency range.optimum guess for the highest eigenfrequency would be: 100GHz.

can you comment why i am always getting this error no matter which uppper frequency i set.

also as mentioned by prafuldeo your generated dispersion figure has phase as x axis where as in the paper we have wave vecter beta.

can you comment how you combine the figures generated by cst mws to get the final dispersion diagram

regards

Hi all,

to have the dispersion diagram in function of the wave vector you have to:

1/ do the same thing as before

2/Then in template based processing load the results with "Load 1D result (or datafile don't remember).."

3/ Do also in template based processing: 1d result from 1d result and choose Rescaling

You can rescale the results in function of what you want so you have just to multiply the phase by 2*pi/d where d is the periodicity

Hope you will understand

@sahid78: I will try to check this, I have no answer for now I don't use eigenmode often.

Just for know: what are you working on prafuldeo and sahid78?

regards

hi piboo

well thanks for your reply but i am still not sure how u generated the dispersion figure out of cst mws.
the figure which you uploaded is showing phase along x axis from 0 to 180 and you having mentioned legends as frequency of mode 1 and frequency of mode 2.

now what i know is you have to run the simulation 3 times for each mode.
1 from Γ to X point of Brillion zone
2 from X to M point
3 from M to Γ point

and in each case phase will be varying from 0 to 180 degree

and in the end you have to combine the 3 simulation results to get the final result figure for each mode

so the x axis scale should be from 0 to 540 degree for the final figure but in you case its only from 0 to 180 ? any comment on that

now i dont know how to manipulate the final figure to get the same figure as in the seivenpiper paper

regards

hi sahid78

I haven't answer for now (I just try like this but seems correct). I will check it (I'm not using dispersion diagram I just try it).

regards

Dear Shahid78,

I believe we're working on the same thing! I've done the dispersion diagram in the HFSS, and am now trying to get it done in CST. Let me know if you're interested.

I am now however having problems in plotting my dispersion diagram, because my unit cell is anisotropic! Do you have any idea of how to go about this? How do I decide where is the Brillouin zone for an anisotropic unit cell?

Thanks alot!
RFgirl

PS:
Dear Piboo,

I've downloaded your CST project file! Thanks alot!
One question tho, what is the port 1 on the zmax for?

Thanks,
RFgirl

Hi RFgirl,
Have you got results in CST?

Regards
Praful

dear RFgirl

well i am still trying to get the dispersion diagram for the isotropic unit cell using CST. so i am unable to give you any advice on anisotropic unit cell

however as you told you were able to get dispersion diagram using HFSS so it would be great if you upload ur HFSS model for dispersion diagram
i think then we can both discuss how to use the same procedure in CST to get the dispersion diagram as normally all 3D electromagnetic software share many common things even though they might be using different numerical methods.

i hope you agree with me

Hello friends,
Any updates with generating dispersion diagram in CST? Please upload it if you got any results. Thanks.

Regards
Praful

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