Simulating FSS in CST MW Studio

Hi
i am simulating fss in cst mw studio. First i am using the example discussed in PDF document "frequency selective surfaces " by REmsky in which we have an annular ring on a dielectric substrate . They have simulated it with hfss and got minimum transmission coefficient at almost 9 Ghz but i am getting it at near6 Ghz. i dont know why
What i am doing is , i am taking plane wave with e vector in x direction and boundary conditions with x as perfect electric, y perfect magnetic , zmax as open and zmin as electric. am i doing right
please help me

Hi shahnazyasir,

1/I think you must try to use a waveguide port instead of a plane wave:

You use PEC and PMC boundaries conditions, this choice is due to have the electric and magnetic field orthogonal so it's a good choice when you use a waveguide port.

But in the case of the plane wave E and H are already orthogonal so you don't need to use this boundaries conditions. For plane wave you must use periodic conditions to have an infinite structure.

2/ If you use a plane wave like this you don't have any reference of the incident field and reflected. There is a macro to simulate phase reflexion of a FSS / EBG / HIS etc...

If you use a waveguide port with PEC and PMC conditions and you put the reference's port to the surface of your structure, CST will simulate S-Parameter and you will have magnitude and phase reflexion of your structure.

Hope you will understand and help you,

Regards

Piboo

actually i want to simulate a subreflector which is reflective for infrared and transperant for ka band and it will be in far field of horn antenna thats why i am using plane wave simulation , i am trying to get frequency response by using probe. if its correct way to get frequency response
and also can anybody guide for the design of fss at infrared
thanks

You want to determine the reflected field by your surface.
As I explain before, by using plane wave and probe, you need to do 3 simulations: you need to simulate the field in free space, on a pec and finally in your structure.
Then a macro calculate the reflected field by your surface.

If you just do the simulation with a probe and plane wave sending on your surface you will not have the reflected field: you will also have the incident field in the response. You can check it in cst by viewing the signal.

You can use the other method with a waveguide port which is really faster.

And for the design of a fss at infrared I can't help you but maybe look the Munk's book: "Frequency Selective Surface: Theory and Design"

regards

actually i want to simulate a subreflector which is reflective for infrared and transperant for ka band and it will be in far field of horn antenna thats why i am using plane wave simulation , i am trying to get frequency response by using probe. if its correct way to get frequency response
and also can anybody guide for the design of fss at infrared
thanks

Sorry same post was sent again by mistake, i will try to simulate with waveguide and hoping that ,will get some results
thanks

Hi Piboo:
Thanks for your kind help. I am still confused a bit. i am using CStMWS version 4. I have read in this forum that i should define an embeded port but there is no option availabe for this , so kindly can you tell me how to define a waveguide port. May be it seems very easy question but please i am a new user of cst
Thanks

Hi shahnazyasir,

I had never used CST v4 so I don't think how I can help you...

But since the version 2006 (the first I have used) you have an option to fix the reference plane to the surface of your structure.

You can find in this forum a topic about plotting phase reflexion using a wavguide port.

regards

piboo

Dear shahnazyasir,
When you define the waveguide port there are two fields Zpos and Distance to reference plane .. so fill it and see if u get the desired results..

Praful

hello:
i am sending the model of my example with results, i am using the example explanied at page 19 of the pdf docment attached here. i am not getting the same results , please do tell me where i am making mistake.
While defining wavegudie port, when i give zpos at the surface of structure i.e. .66mm this error come , waveguide for port 1 is too short. please explain me why this occurs and how much much should be the dist to refrence plane?

With regrds

aslamo alykom shahinaz,see that link,it may help u
https://www.edaboard.com/viewtopic.p...hlight=abdoeng

Added after 39 seconds:

also see that one
https://www.edaboard.com/viewtopic.p...hlight=abdoeng

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

i am beginner. is it easy to learn cst to simulate fss structure

Hello David,
One your simulation is over goto 2D results > Port modes > e or h and you can see which mode is exciting.

Regards
Praful