# Discussion Forum

## electromagntic propagation through three layers

 Topics: 4.1, RF Module
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Belbey Hayet

January 18, 2013 10:54am UTC

electromagntic propagation through three layers

hello
I am student on electronic and I am trying to simulate with comsol on rf module , in summarize my work is to simulate the sun light propagation through three layers bonded to each other and I had used the floquet periodic condition and this witch include this equations :

Parameter

lambda0= 0.5e-6[m]
k0_emwh = 2*pi/lambda0
alpha1 =30[deg]
n1 1.97235
k1x= k0_emwh*real(n1)*cos(alpha1)
k1y =k0_emwh*real(n1)*sin(alpha1)
freq c/lambda0
c= 3*10^8[m/s]
n2 0.125
alpha2= asin(sin(alpha1)*real(n1/n2))
k2x= k0_emwh*real(n2)*cos(alpha2)
K2y= k0_emwh*real(n2)*sin(alpha2)
n3 1.97235
alpha3 =asin(sin(alpha3)*n2/real(n3))
E0z= exp(-i*k1x*x)
Ez1= E0z[V/m]
k3x= k0_emwh*real(n3)*cos(alpha3)
k3y= k0_emwh*real(n3)*sin(alpha3)

and I put the boundary condition above and below the layers
Periodic condition 1
K vector for folquet periodicity :
k1x
k1y
Port 1
In the front of the layer
Put the wave excitation in this port (on)
Pin=1
Téta(in) = 0
E0= Ez1
Beta =k1y
Port 2
Put the wave excitation in this port (off)
E0= Ez1
Beta =k1y

in this simulation i would like to study the propagation of the electromagnetic wave through three micrometer thickness of material, and each material have property , and my problem when reduce the thickness the electromagnetic wave propagate with difficulty and when i increase the thickness the wave propagate easily, i don't know if my simulation is true.

Sergei Yushanov
Certified Consultant
AltaSim Technologies, LLC

January 18, 2013 4:22pm UTC in response to Belbey Hayet

Re: electromagntic propagation through three layers

Belbey,

1) Expressions such as E0z= exp(-i*k1x*x) should be defined under Model>Definitions>Variables but not under Global Definitions>Parameters as in your model, since E0x depends on spatial coordinates. That is why your parameter is highlighted as red.

2) Propagation constant in the port conditions should be normal component of the wavector, not parallel. That is, beta=k1x and not beta=k1y as in your model.

3) I assume you want to analyze TE polarization. In that case, incident wave should be defined as E={0,0, exp(-i*k1y*y) }, not E={0,0,exp(-i*k1x*x)} as in your model.

4) Consider creating mesh with several elements through the thickness of the thin middle layer using Mapped mesh.

5) If you are not sure about your results, compare Comsol results with analytical solution for multilayer structures available in textbooks. Numerical and analytical solutions should be in perfect agreement for all incidence angles for 0 to 90 degrees.

Regards,
Sergei

Belbey Hayet

January 19, 2013 7:50am UTC in response to Sergei Yushanov

Re: electromagntic propagation through three layers

thank you sergai

I'll try i'll try to change what are you had tell , just I would like tell you i use the floquet periodic condition, i suppose it's the same , i ll give you the results that i found

Belbey Hayet

January 19, 2013 11:29am UTC in response to Belbey Hayet

Re: electromagntic propagation through three layers

hello sergai

I redid my simulation with your modification but it's the same results , and in this simulation i want to study the electromagnetic wave propagation through x axes , can you help me please .

thank you

Sergei Yushanov
Certified Consultant
AltaSim Technologies, LLC

January 21, 2013 5:56pm UTC in response to Belbey Hayet

Re: electromagntic propagation through three layers

Belbey,

I don’t have 4.1, so I am attaching report of your model created with later version. Comparison with analytical solution for the case of TM polarization is also included.

I set the conductivity of the first ZnO layer to zero because it does not make much sense to specify evanescent wave at the input port. If you want to study wave attenuation in the first ZnO layer, then you might want to model structure with four layers: first layer is lossless dielectric (say, air) where you specify incident wave, second layer is ZnO with specified thickness, etc.

Regards,
Sergei

Belbey Hayet

January 27, 2013 11:21am UTC in response to Sergei Yushanov

Re: electromagntic propagation through three layers

thank you sergai for your answer , i will trying this and i give the news

SR

January 27, 2013 6:58pm UTC in response to Sergei Yushanov

Re: electromagntic propagation through three layers

Could you please attach the mph file; thank you!

Belbey Hayet

January 27, 2013 7:31pm UTC in response to SR

Re: electromagntic propagation through three layers

of course

Sergei Yushanov
Certified Consultant
AltaSim Technologies, LLC

January 28, 2013 5:56pm UTC in response to SR

Re: electromagntic propagation through three layers

SR,

Attached is model file. Please note that this is 4.3a.

Regards,
Sergei

Belbey Hayet

January 29, 2013 9:09am UTC in response to Sergei Yushanov

Re: electromagntic propagation through three layers

thank you sergai

I don't have 4.3 A version , but I am trying to work under 4.1 version with you last exemple , when I finish I post the result

Belbey Hayet

January 29, 2013 1:42pm UTC in response to Belbey Hayet

Re: electromagntic propagation through three layers

hello ,

I have a small problem with parameter equation when i try to enter this equation in parameter case

sqrt(k0^2*em - kay^2 - j*eps^3)

x-component of wavevector of middle layer (evanescent square root)

the comsol don't accept this , and I would like to know what the
eps

thank you

Sergei Yushanov
Certified Consultant
AltaSim Technologies, LLC

January 29, 2013 2:41pm UTC in response to Belbey Hayet

Re: electromagntic propagation through three layers

Belbey,

eps is small number. Under Global Parameters, define a=eps and you will see that it's numerical value is 2.22e-16.
If you define eps1=1e-12, it will be OK.

Sergei

Ivar Kjelberg

January 29, 2013 7:03pm UTC in response to Sergei Yushanov

Re: electromagntic propagation through three layers

Hi

indeed "eps" is a predefined number in COMSOL (as in other numerical tools) it's the smalles real number one can distinguish from "1.0" in the binary representation of real numbers. It's rather FPU dependent, so you can forget to put it to any positive power it will wanish.
Even, as most physics equations are 2nd order PDE's then sqrt(eps) represents, the absolute best, relative ratio, or number of significant digits you could expect from your results

--
Good luck
Ivar

Belbey Hayet

January 30, 2013 10:31am UTC in response to Ivar Kjelberg

Re: electromagntic propagation through three layers

Hi sergai

this is what I've done but it's still wrong , but the notation in certain parameter indicate with red color , please if some one can correct me ,i am always trying to find a solution , in parallel if i find something i poste

thank you

Ivar Kjelberg

January 30, 2013 6:04pm UTC in response to Belbey Hayet

Re: electromagntic propagation through three layers

Hi

red means normally typos, or undefined variable name:s so those should be tracked and corrected,
orange is unit inconsistencies, thise might be ignored, with the risk of scaling errors

--
Good luck
Ivar

Belbey Hayet

March 7, 2013 8:32am UTC in response to Ivar Kjelberg

Re: electromagntic propagation through three layers

Hi ,

just I finished my simulation through the last exemple , but in last part from the example i don't understand how to obtain the diagram refraction in 1 D plot groupe can help you me to have the diagrme
thank you

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