Calculating transmission and reflection coefficients of a multilayered structure

@wim
Sorry but please correct me ... after defining substrate layers, the next step to draw the design is to draw ploygons (rectangles in my case) at specified thicknesses and then to give the excitation. I had for example taken 100x100 as the dimensions of these rectangles(xy-plane) but now I want infinite dimensions in xy plane so what should the dimensions of these rectangles be(this is what I meant by "infinite polygons")? Also when you say "when you build polygon you get metal"......with my approach( may be wrong) I will get metal with my dielectric layers.

I am confused now. Do you want infinite size metallic or dielectric?

You are correct, when you draw a polygon (and don't convert it into a dielectric layer afterwards), you "paint" metal at the selected heigth. You can't model an infinite ground plane by drawing a polygon as this leads to infinite number of segments.

Why you want an infinite size polygon? I don't see the relations with your #1 posting.

Sorry, I think I am not able to make my point clearly.
As suggested by you in #6 , I want infinite dielectric in xy plane.I definitely don't want any metallic layer in my structure.
It seems my approach is not correct. Please tell me that after defining substrate layers in "basic parameters" how should I proceed to make my design? Shouldn't my design look like in the picture that I uploaded?

OK, this makes sense.

By default, dielectric layers you define have infinite size, no matter the presence of metallic polygons. In 3D view, dielectric layers don't look like infinite (but sure they are).

I still have a doubt..... after I define the dielectric layers and click OK in basic parameters window, polygon editor opens up. Please tell me how should I design my problem there.I design by drawing polygons whose dimensions need to be entered. If this is correct how should these dimensions be selected and do they have to do anything with xy plane?

Sorry, I am confused again, why would you need metallic polygons when having plane wave port option?

Ok. Let me put it in this way....What steps should I take after the polygon editor window opens up?

Are you trying to measure thickness of layers?
I have seen cell membranes and other similar structures modeled.

Why are you operating at 400Meg?
Why cant Impedance spectrometer and modeling retreive the data?

Mona7150 said:

Hello all,

I have to determine S11 and S21 for a planar multilayered structure ( different layers with different permitivities stacked on each other). The thickness of different layers is fixed only in one dimension(say Z-axis,total thickness in Z direction is almost 150mm). My frequency of operation is around 403MHz. I tried doing it with CST and HFSS but since they are 3D software so I am not able to understand what thickness should be kept in the other two axis(x and y axis) because the results change as I change these dimensions. Moreover do I need to make some changes in mesh settings?
Can anybody please suggest some other way of solving the problem?


Thank You

Click to expand...

When in the basic parameters menu set up your dielectric layers AND set conductivity = 0 for Z=0 layer. Now you have your infinite size dielectric layers without any metal structure.

Your version seems to have plane wave ports, so you can continu setting up your ports. I don't know your version exactly, but if yo get complaints about Z<0, you may need to raise your dielectric sandwich.

@wim

I am working in MGRID. I am not sure how will I define the port without drawing any ploygons. I will try to implement the way you said and get back to you.

Thanks


@nicsky

No , I know the thicknesses of all the layers. I have to find the equivalent S11 and S21 of this multilayer structure.

I hope that you can figure out how plane wave excitation with S-parameters functions in IE3D, I didn't even know that it was possible.

When I had to do dielectric things I used plane wave excitation as used for Radar Cross Section analysis and put short dipoles in the vicinity of the dielectric that are "loaded" with a lumped port (vertical or horizontal localized ports).

Before running the simulation I selected current density simulation also. When in the current density view (after the simulation) I set the port voltage to zero, I look to the voltage (or current) at the port with the plane wave excitation present. Based on these values, and the calibration simulations, I calculate the things I want to know by hand.

The calibrations simulations I do just without a dielectric present. When running simulations with dielectric, make sure you set all accuracies to high (the simulator should do this automatically).

As you are requesting vertical incidence only (theta = 0, E- and H-field parallel to media interface), you need to have theta=0 when setting up the plane wave source. The amplitudes and polarization of the plane wave excitation you can specify in the current viewer.

IE3D is no from Mentor and I had only a few hours to experiment with the latest version, so maybe some things have changed.

If you can do it with plane wave S-parameter simulation, it will save you time.

When i have S11 and S21, it is possibile to find the electrical parameters as conductivity, permittivity and permeability?

Thank you

Hello zionico90

yes we can calculate these parameters. Can you please help me setting up my problem in CST?

How i can calculate these parameters?This is my approach:

- characterize a unit cell of material in terms of conducitivity, epsilon and mue;
- create a "normale" material with this tensor;
- create a plane in which overlapping the layer using a "thin or coated" materials;
- set porst and boundary conditions and calculate s-parameters

I don't know how is it done in CST (would like to know), but I have come across certain papers which shows how can we extract these parameters from S11 and S21.
Could you get correct S11 and S21 in CST. Can you help me in setting up a simple problem.

Which is your problem? I recommend you to try to calculate s-parameters for a aluminium panel in order to understand the set up. Have you try it?

No i haven't.. What do you mean by aluminium panel? I have a slab of air(infinite in xy plane) whose S11 I want to know. I tried but I am getting S11=0.9 (but there should not be any reflection in pure air medim)

which is your range of frequency?Which are the settings of the background?Have you try with a OPEN ADD SPACE Boundary?

If you create a brick of aluminium and find s-parameters, you should know the conductivity and are you able to comparared it with the standard value of aluminium.

Iam working in 402-405 MHz. Background material is" normal", boundary conditions being electric in x direction, magnetic in y and open in z. Like you are saying to do a basic example of aluminium, similarly I am doin with a brick of air in which ideally there should be no reflection so S11 should be 0.
Do you know how to excite a TEM mode in waveguide port ? Can I send you my design?

Have you set the frequency range as 402-405 MHz?! Try to modified and set to 0-2Ghz. When i'm in office i try to take a snapshot of my design.