[SOLVED] Obtain dispersion diagram from Eigenvalue Solver CST

cst_newbie · Feb 9, 2013

To all

I have finished my drawing a microstrip and I would like to observe the dispersion diagram (beta versus frequency) from Eigenvalue (Eigenmode) solver from CST. And I am supposed to obtain the dispersion diagram from Results File --> 1D Results. But I can't see any graph or results relate with it. How can I set the graph function and so that I am able to obtain the dispersion diagram?

For your information, I am applying PBC (Periodic Boundary Condition) at the z-axis which corresponding to my micostrip. Please let me know if you need a file and I am using CST version 11.

P/S: Please forgive me if I made some English grammar mistakes.

Hope to get reply from anyone of you soon. It is quite urgent, many thanks.

Regards
cst_newbie

StergiosP · Feb 9, 2013

Usually one needs to setup a parameter sweep (with the phase shift being the parameter). The dispersion diagram then can be found under the "tables" folder. It would be useful if you can provide some more info about your design or even better if you could upload the cst project....

cst_newbie · Feb 9, 2013

StergiosP said:
Usually one needs to setup a parameter sweep (with the phase shift being the parameter). The dispersion diagram then can be found under the "tables" folder. It would be useful if you can provide some more info about your design or even better if you could upload the cst project....

Hi, thanks for your reply and here I attached my cst file.View attachment Unit Cell Approach to Full-Wave Analysis of Meander Delay Line Using FDTD Periodic Structure Mod.pdf

For your information, I am using CST version 11.

I will extend more information about what I am doing now. Basically, I need to use the values from the journal as I attached to obtain the dispersion diagram as shown in page 4 figure 7.

Anybody can check whether my modeling for the meander line is correct?

As we can see, under port information, there is a beta graph, does this graph represents the dispersion for the meander line or it has another meaning behind it?

If not, how can I add the dispersion relation in my modeling.

Many thanks for your patient and reply.

cst_newbie · Feb 11, 2013

View attachment One single turn (PBC).ziphere is the attachment.

StergiosP · Feb 11, 2013

I had a look at your files (e.g. for 0.4mm) and I noticed the following:

1. You are exciting the structure with ports, and thus you do not use the eigenmode solve as you say in the original post. The standard way to get the dispersion diagram is with the eigenmode solver (i.e. without excitation). If you excite your structure you need to do quite a few steps. I suggest to use the eigenmode solver as this will save you a lot of time and will keep you away from many potential error sources.

2. You apply periodic boundaries along the y-direction but from my understanding (after having a quick look at the paper) the structure in your design should be periodic along the x-direction.

Now, if you follow the above steps, in the boundary setup window, under the phase shift tab you can define a variable for the phase shift along the direction that you applied the periodicity (e.g. kx for the x- dir). Enter an arbitrary value to start with. Next, select he eigenmode solver and hit the param. Sweep tab. Define a new sequence and use kx for the parameter sweep. Enter start/stop values for kx (0-180 deg) and the number of points inbetween. On the right hand side of the window monitor the frequency of the modes you are interested in. Finally, click start. This will generate automatically the dispersion diagram under the folder" tables". Then you can easily get the graph you want by normalizing the axis.

Hope this helps....

cst_newbie · Feb 14, 2013

StergiosP said:
I had a look at your files (e.g. for 0.4mm) and I noticed the following:

1. You are exciting the structure with ports, and thus you do not use the eigenmode solve as you say in the original post. The standard way to get the dispersion diagram is with the eigenmode solver (i.e. without excitation). If you excite your structure you need to do quite a few steps. I suggest to use the eigenmode solver as this will save you a lot of time and will keep you away from many potential error sources.

2. You apply periodic boundaries along the y-direction but from my understanding (after having a quick look at the paper) the structure in your design should be periodic along the x-direction.

Now, if you follow the above steps, in the boundary setup window, under the phase shift tab you can define a variable for the phase shift along the direction that you applied the periodicity (e.g. kx for the x- dir). Enter an arbitrary value to start with. Next, select he eigenmode solver and hit the param. Sweep tab. Define a new sequence and use kx for the parameter sweep. Enter start/stop values for kx (0-180 deg) and the number of points inbetween. On the right hand side of the window monitor the frequency of the modes you are interested in. Finally, click start. This will generate automatically the dispersion diagram under the folder" tables". Then you can easily get the graph you want by normalizing the axis.

Hope this helps....

Hi, thanks for your help and I managed to get it done.

akhileshgupta9 · Mar 7, 2013

cst_newbie said:
View attachment 86879here is the attachment.

ersion of cst

sir
i am using cst 10 version and unable to find newer version so please help me to access this cst file
akhileshgupta9@gmail.com

cst_newbie · Mar 7, 2013

akhileshgupta9 said:
ersion of cst

sir
i am using cst 10 version and unable to find newer version so please help me to access this cst file
akhileshgupta9@gmail.com

Which CST file that you meant?

amntt · Jun 13, 2013

hi anybody there? i whant to plot dispersion diyagram for a structure which has lumped element that are connected to the structure with discrete port . how i can plot dispersion diagram?

akhileshgupta9 · Jun 14, 2013

StergiosP said:
I had a look at your files (e.g. for 0.4mm) and I noticed the following:

1. You are exciting the structure with ports, and thus you do not use the eigenmode solve as you say in the original post. The standard way to get the dispersion diagram is with the eigenmode solver (i.e. without excitation). If you excite your structure you need to do quite a few steps. I suggest to use the eigenmode solver as this will save you a lot of time and will keep you away from many potential error sources.

2. You apply periodic boundaries along the y-direction but from my understanding (after having a quick look at the paper) the structure in your design should be periodic along the x-direction.

Now, if you follow the above steps, in the boundary setup window, under the phase shift tab you can define a variable for the phase shift along the direction that you applied the periodicity (e.g. kx for the x- dir). Enter an arbitrary value to start with. Next, select he eigenmode solver and hit the param. Sweep tab. Define a new sequence and use kx for the parameter sweep. Enter start/stop values for kx (0-180 deg) and the number of points inbetween. On the right hand side of the window monitor the frequency of the modes you are interested in. Finally, click start. This will generate automatically the dispersion diagram under the folder" tables". Then you can easily get the graph you want by normalizing the axis.

Hope this helps....

is there need to place airbox above the ebg structure if yes ,what should be the dimension of airbox (airbox>box who's material is vacuum)

[SOLVED] Obtain dispersion diagram from Eigenvalue Solver CST

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